# African Herbal Remedies with Antioxidant Activity: A Potential Resource Base for Wound Treatment

Authors: Mary Gulumian; Ewura Seidu Yahaya; Vanessa Steenkamp
Journal: Evidence-Based Complementary and Alternative Medicine
 (2018)

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## Abstract

The use of traditional herbal remedies as alternative medicine plays an important role in Africa since it forms part of primary health care for treatment of various medical conditions, including wounds. Although physiological levels of free radicals are essential to the healing process, they are known to partly contribute to wound chronicity when in excess. Consequently, antioxidant therapy has been shown to facilitate healing of such wounds. Also, a growing body of evidence suggests that, at least, part of the therapeutic value of herbals may be explained by their antioxidant activity. This paper reviews African herbal remedies with antioxidant activity with the aim of indicating potential resources for wound treatment. Firstly, herbals with identified antioxidant compounds and, secondly, herbals with proven antioxidant activity, but where the compound(s) responsible for the activity has not yet been identified, are listed. In the latter case it has been attempted to ascribe the activity to a compound known to be present in the plant family and/or species, where related activity has previously been documented for another genus of the species. Also, the tests employed to assess antioxidant activity and the potential caveats thereof during assessment are briefly commented on.


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## Body

## 1. Introduction

Human cells are continuously exposed to exogenous oxidants as well as to those produced endogenously during normal physiological processes. Antioxidants form part of protective mechanisms that exist in human cells to scavenge and neutralize these oxidants. Oxidants such as the reactive oxygen species (ROS) and reactive nitrogen species (RNS) are involved in several diseases [1, 2]. Antioxidant defenses are defective in these diseases and therefore it is possible to limit oxidative damage and ameliorate disease progression with antioxidant supplementation [3].With reference to wounds, antioxidants play pivotal roles that consequently restore normalcy to injured skin. Basal levels of ROS and other free radicals are essential in almost all phases of the wound healing process (Figure1) [4]. During haemostasis, ROS regulates the constriction of blood vessels to limit loss of blood. Furthermore, ROS facilitates the migration of neutrophils and monocytes from surrounding blood vessels towards the injury site. The presence of ROS and other free radicals in the wound vicinity during the inflammatory phase of the healing process is also required for infection control and general maintenance of sterility. Finally, ROS promotes the proliferation of keratinocytes, endothelial cells, and fibroblasts, thereby enhancing angiogenesis and collagen deposition. However, uncontrolled release of ROS could cause oxidative stress, resulting in cellular and tissue damage, thereby causing delayed healing [1].Figure 1
Role of reactive oxygen species (ROS) in the wound healing process.To keep ROS within physiological levels, antioxidants serve as electron donors, thereby preventing them from capturing electrons from other molecules which ultimately leads to their destruction [4]. Both nonenzymatic antioxidants such as glutathione, ascorbic acid, and α-tocopherol, as well as enzymatic antioxidants like catalase and peroxiredoxin, have shown potential to normalize high ROS levels and thus stimulate healing [4]. By normalizing ROS, antioxidants can enhance their physiological roles and thereby accelerate the wound healing process. Naturally occurring antioxidants are generally favoured over their synthetic counterparts, as the latter are suspected to cause or promote negative health effects [5]. This has resulted in the restricted use of synthetic antioxidants in several countries [6].This review provides a comprehensive list of African medicinal plants and isolated compounds with antioxidant activities, with the aim of highlighting the continent’s rich herbal resource base for possible management of wounds and allied conditions. Previous reviews have listed a number of these African medicinal plants with antioxidant properties [7–9]. The present work has therefore aimed to expand the list to include medicinal plant species with antioxidant properties that are used in different African countries including those from Madagascar and Mauritius. For the sake of inclusivity, plants that have been shown to contain compounds that hold the potential of being novel antioxidants are also considered. In addition, those with anti-inflammatory properties were also included due to an earlier observation that the anti-inflammatory activities of the same extracts could be explained, at least in part, by their antioxidant properties [10]. Additional efforts were also made to include information, where available, on their vernacular names, their regional distribution, and medicinal use and plant parts used for these preparations or for the isolation of the antioxidant ingredient(s). Table 1 lists medicinal plants that have been investigated and have confirmed antioxidant and/or anti-inflammatory activity and that contain compounds which are known to have such activities. Table 2 on the other hand lists medicinal plants that have confirmed antioxidant activity but the compounds responsible for their antioxidant property have not yet been identified.Table 1
Medicinal plants with confirmed antioxidant activity, shown to contain compounds that are known to have such activity.
Family and plant name Vernacular name Plant part Country/area Medicinal use and/or experimental validation Compounds isolated Reference Aloaceae  Aloe barbadensis Mill. Burn plant,siber, sbar/essouktouri /mar, sbar Leaf exudate Algeria, Morocco, Tunisia Antioxidant activity.Used as laxative, purgative, diuretic, asthma, baldness, cuts, bounds, skin rash. Flavonoids, two dihydrocoumarin derivatives and two flavone glycosides [32–34]  Aloe claviflora  Burch. Kraal aloe Leaf exudate South Africa Radical scavenging activity and moderate activity in the lipid peroxidation assay Chromone glycoside [35, 36]  A. saponaria (Ait.) Haw. MpeluMnemvuSoap aloe, African aloe Leaf exudate South Africa Radical scavenging activity and moderate activity in the lipid peroxidation assay Chromone glycoside [35, 37]  A. thraskii  Baker Dune aloe, ikhala, umhlaba Leaf exudate South Africa Radical scavenging activity and moderate activity in the lipid peroxidation assay Chromone glycoside [35, 36]  Amaranthaceae  Amaranthus caudatus L. Tassel flower Seed;Young shoots Ethiopia Antioxidant properties Tocopherols, phenolic acids [38–40]  Anacardiaceae  Anacardium occidentale L. Not signalized Stem-bark Nigeria Anti-inflammatory properties. Agathisflavone, quercetin 3-O-rutinoside, quercetin 3-O-rhamnoside [41, 42]  Lannea edulis Engl. Wild Grape Root-bark Zimbabwe Semipolar extracts high activity both as radical scavengers and lipoxygenase inhibitors. Lipophilic extracts inhibitor of 15-lipoxygenase.Used for painful menstruation, urogenital infection, sexually transmitted diseases. Two alkylphenols (cardonol 7 and cordonol 13) and three dihydroalkylhexenones [43–45]  Lannea velutina A. Rich BemmbeyiRaisinier velu, Lannéa velouté Leaves, bark, root Mali Antioxidant properties Proanthocyanidins [46, 47]  Mangifera indica L. MangoMangoro Leaves, seeds,stem-bark BeninBurkina Faso Anti-inflammatory, analgesic, and hypoglycemic effects.Used to treat urogenital infection, tonic, diarrhoea, tooth ache, gingivitis, liver disease, diabetes. Polyphenolics, flavonoids [12, 13, 46, 47]  Apiaceae  Centella asiatica (L.) Urb. Gotu kola Leaves South Africa Antioxidant and anti-inflammatory activities.Used for wound healing. Protection against radiation-induced injury.Cardio protective effect.Oral treatment increased antioxidant enzymes. Quercetin and tetrandrine [48–55]  Apocynaceae  Alstonia boonei De Wild. Awun,Egbu Stem-barkRoot-bark NigeriaGhana Anti-inflammatory activity.Used for its analgesic and anti-inflammatory properties. Rutin, Quercetin robinobioside,Kaempferol-3-O-rutinoside, Kaempferol-3-O-robinobioside [56–59]  Catharanthus roseus  (L.) G. Don Madagascarperiwinklekaka poul, karaktè dezosm blan, zèb sosyé Whole plant Madagascar Antioxidant activity and ability to increase antioxidant enzymes.Used for conjunctivitis. Phenols [60]  Arecaceae  Elaeis guineensis Jacq. Ori Nuts Ghana  Nigeria Anti-inflammatory activity.Used to treat rheumatoid arthritis. 3,4 hydroxybenzaldehyde, p-hydroxybenzoic acid, vanillic acid, syringic acid, ferulic acid, carotenoids,α-tocopherol [12, 61]  Asclepiadaceae  Secamone afzelii Rhoem. AhabanKroratima Stem Central Africa Antioxidant and anti-inflammatory properties.Used for wound healing. Flavonoids, caffeic acid derivatives andα-tocopherol. [62–64]  Asphodelaceae  Bulbine capitata Poelln. Scented grass bulbine RootsAerial parts South Africa Anti-inflammatory and weak antioxidant and free radical scavenging and lipid peroxidation inhibition activities.Knipholone as a selective inhibitor of leukotriene metabolism.Used as a mild purgative and to cure gonorrhoeal infections. Anthraquinone Knipholone [65–73]  Bulbine frutescens Willd. Snake flower, cat’s tail,burn jelly plant Leaf juiceRoots South Africa Anti-inflammatory and weak antioxidant and free radical scavenging and lipid peroxidation inhibition activities.Knipholone is a selective inhibitor of leukotriene metabolism.Used to treat burns, rashes, blisters, insect bites, cracked lips, acne, cold sores, mouth ulcers and areas of cracked skin. Phenylanthraquinones,Isofuranonaphthoquinones,Gaboroquinones A and B and 4′-O-demethylknipholone-4′-O-beta-D-glucopyranoside, and Knipholone (anthroquinone) [65, 67, 70, 74, 75]  Kniphofia foliosa Hochst. Red-not-peker  Kenya Anti-inflammatory and weak antioxidant and free radical scavenging and lipid peroxidation inhibition activities. Knipholone as a selective inhibitor of leukotriene metabolism.Used for abdominal cramps, wound healing Anthraquinone: Knipholone [65, 76–78]  Asteraceae  Artemisia abyssinica Sch.Bip. Chikugn (Amharic)Arrtta bera (Or) Whole plant Ethiopia Radical scavenging and antioxidant activities.Used for stomach pain and wound healing. Essential oils and flavonoids [79–82]  A. afra Jacq.  ex Willd. African wormwoodWild wormwood Roots, stems and leaves EthiopiaSouth Africa Radical scavenging and antioxidant activities.Used for stomach pain, coughs, colds, fever, loss of appetite, colic, headache, earache, intestinal worms to malaria. Essential oils and flavonoids [79, 82–84]  A. arvensis L. MugwortWormwood Whole plant Algeria Radical scavenging and antioxidant activities. Phenolic compounds and flavonoids. [85]  A. campestris L. Field sagewort Field wormwood Whole plant Algeria Radical scavenging and antioxidant activities.Used to treat insomnia Phenolic compounds and flavonoids. [85–87]  Bidens pilosa L. Black jack LeavesRoots South Africa Antioxidant and anti-inflammatory, antibacterial, antihypertensive activities.Used to treat diabetes and backache. Phenolic compounds: quercetin 3-O-rabinobioside, quercetin 3-O-rutinoside.Two novel methoxylated flavone glycosides: quercetin 3,3′-dimethyl ether 7-O-c¢-L-rhamnopyranosyl-(1 ~ 6)-fl-D-glucopyranoside and the known quercetin 3,3′-dimethyl ether 7-O-fl-D-glucopyranoside [19, 88–91]  Cynara scolymus L. Globeartichoke Leaves Ethiopia Antioxidative and lipid-lowering properties and eNOS up-regulating ability.Used to treat chronic liver and gall bladder diseases, jaundice, hepatitis and atherosclerosis. Polyphenolic flavonoid compounds [14, 15, 92, 93]  Helichrysum dasyanthum Sweet Afrikaans common name of kooigoed (bedding material) Leaves South Africa Antioxidant, radical scavenging and anti-inflammatory activities.Used to treat wounds, infections, respiratory conditions. Essential oils [94–96]  H. petiolare Hilliard & B.L. Burtt. Everlasting, Imphepho Leaves South Africa Antioxidant, radical scavenging and anti-inflammatory activities.Used to treat wounds, infections, respiratory conditions, asthma, chest problems and high blood pressure Essential oils [94–96]  Tagetes minuta L. Khaki bushstinking rogermuster John Henry, wild marigold Leaves Madagascar Antimicrobial and antioxidant activity.Used as anthelmintic, antispasmodic, purgative and for the treatment of gastritis, indigestion and internal worms. Essential oils. [23, 97]  Balanophoraceae  Thonningia sanguinea Vahl. Nkomango Roots Ghana Antioxidative and radical scavenging activities and lipid peroxidation inhibitory activity.Used for bronchial asthma, rheumatoid arthritis, atherosclerosis and diabetes. Ellagitannins: Thonningianin A and B [98–103]  Balanitaceae  Balanites aegyptiaca (L.) Delile Hausa: aduwaDesert date Bark and roots East Africa Antioxidant propertiesin vitro confirmed.The bark and roots are used as laxatives, and for colic. The bark is used for sore throats, and as a remedy for sterility, mental diseases, epilepsy, yellow fever, syphilis, and tooth aches. Coumarins, flavonoids, saponins (Balanin 1 (3β,12β,14β,16β) cholest-5-ene-3,16-diyl bis (β-d -glucopyranoside)- 12-sulphate, a new sterol sulfonated and Balanin 2 (3β,20S,22R,25R)-26-hydroxy-22-acetoxyfurost-5-en-3- yl-rhamnopyranosyl-(1→2)-glucopyranoside, a novel furostanol saponin) [11, 104–106]  Bignoniaceae  Jacaranda mimosaefolia D.Don. Sharpleaf Jacaranda LeavesStem-bark Nigeria Shown to have antimicrobial activity and used to treat infections Phenylethanoid glucoside, jacaranone [107–109]  Spathodea campanulata P.Beauv. African tulip Stem-bark Nigeria, Ghana,Cameroon (Yaounde region) Anti-inflammatory, antioxidant, hypoglycemic, anticomplement and anti-HIV activities.Used to treat itching, arthritis, and diabetes. Flavonoids and caffeic acid derivatives [63, 110]  Tecoma stans (L.)H.B. & K. Yellowtrumpet bush LeavesStem-bark Nigeria Anti-diabetic activity is shown. 4-O-E-caffeoyl-alpha-L-rhamnopyranosyl-(1′→ 3)-alpha/beta-D-glucopyranose, E/Z-acetoside, isoacetoside [107, 111]  Capparaceae  Cleome arabica L. Cleome efeina Leaves Egypt Antioxidant activity, inhibited lipoxygenase activity and calcium ionophore-stimulated LTB4 synthesis in human neutrophils.Used to treat wounds and prevent inflammation Rutin and quercetin. [112, 113]  Clusiaceae  Garcinia kola Heckel Bitter cola/aku ilu, agbu ilu.NigeriaHausa:Góórò pl. gwârráá or gòòràrràkáí Seeds Nigeria Inhibit lipid peroxidation and protective against H2O2-induced DNA strand breaks and oxidized bases.Used for laryngitis, coughs, liver disease, bronchitis and throat infections. Inhibits Aflatoxin B1 induced genotoxicity. Biflavonoid: kolaviron [114–120]  Harungana madagascariensis Poir. Otori Stem-bark Eastern Nigeria Significant antioxidant activity.Used to treat skin diseases. Prenylated Anthronoids: harunmadagascarin A [8,9-dihydroxy-4,4-bis-(3,3-dimethylallyl)-6-methyl-2,3-(2,2-dimethylpyrano)anthrone], harunganol B [121–123]  Hypericum carinatum Griseb. Not signalized Leaves Egypt Antioxidant and radical scavenging activities. Benzophenones: cariphenone A (6-benzoyl-5,7-dihydroxy-2,2,8-trimethyl-2H-chromene) and cariphenone B (8-benzoyl-5,7-dihydroxy-2,2,6-trimethyl-2H-chromene). [124, 125]  H. perforatum L. Common St.-Johns’ wort Whole plant Egypt Anti-inflammatory and anti-oxidant activities. Free radical scavenging, metal-chelation, and reactive oxygen quenching activities. Protective against scopolamine-induced altered brain oxidative stress status and amnesia in rats. Ability to suppress the activities of 5-lipoxygenase (5-LO) and cyclooxygenase-2 (COX-2), key enzymes in the formation of proinflammatory eicosanoids from arachidonic acid (AA).Analgesic, antiseptic, antispasmodic, digestive, diuretic and sedative. Flavonoids: Rutin, hyperoside, isoquercitrin, avicularin, quercitrin, and quercetin. [124, 126–131]  Cochlospermaceae  Cochlospermum tinctorium A.Rich. N’tiribara Roots Sudan, UgandaWest Africa Antioxidant activity.Used for malaria, jaundice. Polyphenols: gallotannins and ferulic acids [35]  Combretaceae  Combretum woodii Drum. Large-leaved forest bushwillow Leaf South Africa Antioxidant and antibacterial activities. Also tannins showed inhibitory effect on Fe2+-induced lipid peroxidation and radical scavenger activity.Used for pneumonia, syphilis, abdominal pain and conjunctivitis. Polyphenols: Combretastatin B5 (2′,3′4-trihydroxyl,3,5,4′-trimethoxybibenzyl).Tannins. [132–137]  Combretum imberbe Not signified  South Africa Combretum species are widely used for treating abdominal disorders (e.g. abdominal pains, diarrhea) backache, bilharziasis, chest coughs, colds, conjunctivitis, dysmenorrhoea, earache, fattening babies, fever, headache 1α,3β-dihydroxy-12-oleanen-29-oic, 1-hydroxy-12-olean-30-oic acid, 3,30-dihydroxyl-12-oleanen-22-one, and 1,3,24-trihydroxyl-12-olean-29-oic acid, a new pentacyclic triterpenoid (1α,23-dihydroxy-12-oleanen-29-oic acid-3β-O-2,4-di-acetyl-l-rhamnopyranoside) [138]  Guiera senegalensis J.F.Gmel. N’kundjè Leaf Western Africa Antioxidant and radical scavenging activities.Used to treat dysentery, diarrhoea, gastro-intestinal pains and disorders, rheumatism, diabetes and fever. Flavonol aglycones, flavonol glycosides and flavonoids (catechin, myricitrin, rutin and quercetin) as well as tannins (galloylquinic acids (hydrolysable tannins). [139–143]  Terminalia sericea Burch. ex DC. Silver cluster-leaf Bark South Africa Radical scavenging and antioxidant activities.Used to treat diabetes and pneumonia and to relieve colic Pentacyclic triterpenoidsAnolignan B [21, 136, 144]  Commelinaceae  Commelina diffusa Burm.f. Wandering JewClimbing day flower Leaves Ghanna Anti-inflammatory and antioxidant properties.Used to treat fever and is diuretic Flavonoids [63, 145]  Palisota hirsuta K.Schum., Not signified Aqueous leaf extracts Nigeria Anti-inflammatory effects against carrageenan induced hind paw oedema Not identified [146, 147]  Crassulaceae  Bryophyllum  pinnatum  (Lam.) OkenSynonym: Kalanchoe pinnata (Lam.) Pers. Ufu ivo Leaves Nigeria, South Africa Anti-inflammatory properties.Used for earache. Flavonoids, polyphenols, triterpenoids [12, 148, 149]  Cupressaceae  Juniperus procera  Hochst ex. Endl. African Juniper Young twigs and buds Ethiopia Antioxidant and free radical scavenging activities.Used to relieve stomach pain. Essental oils [79, 150, 151]  Dioscoreaceae  Dioscorea dumetorum (Kunth) pax Yam Tubers Nigeria Antioxidant activity to modify serum lipid and anti-inflammatory activity.Used to treat diabetes. Dioscorea and Dioscoretine [152–154]  Drosera madagascariensis  (DC.)D. ramentacea Burchell Sundew Roots and flowers Madagascar Anti-inflammatory effects.Used to treat coughs and asthma Flavonoids: hyperoside, quercetin and isoquercitrin [155, 156]  Drosera rotundifolia L. Round-leaf Sundew Roots and flowers Madagascar Anti-inflammatory effects.Used to treat coughs and asthma Flavonoids: hyperoside, quercetin and isoquercitrin [155, 157]  Euphorbiaceae  Alchornea laxiflora (Benth) Pax & K. Hoffm. Wild banana Leaf and root Nigeria Antioxidant and anti-microbial activity.Used to treat jaundice and liver disorders. Also used in food preservation. Quercetin-7,4′-disulphate, quercetin, quercetin-3′,4′-disulphate, quercetin-3,4′-diacetate, rutin and quercetrin [158–161]  Bridelia ferruginea Benth. Ora Leaves, stemand bark West AfricaDemocratic republic of Congo, Nigeria Anti-inflammatory.Used to treat diarrhea, dysentery, gastro-intestinal disorders, gynecological disorders (including sterility), and rheumatic pains. A bioflavonoid: Gallocatechin-(4′→O →7)-Epigallocatechin. [12, 57, 162–166]  Mallotus oppositifolius (Geiseler) Muell. Arg. JororoKáfàr mútúwààSenampendiMvundza jembe Leaves, roots West AfricaNigeria Antioxidant, anti-inflammatory and antimicrobial activities.Used for abortion. Flavonoids: quercetin and quercitrin. [167–172]  Fabaceae  Aspalathus linearis (Brum. F.) R. Dahlgr. Rooibos Leaves South Africa Radical Scavenging CapacityUsed to treat stomach cramps, insomnia, and to reduce stress. Phenolic Fractions, Tannins and monomeric flavonoids aspalathin, nothofagin, quercetin, rutin, isoquercitrin, orientin, isoorientin, luteolin, vitexin, isovitexin, and chrysoeriol. [16–21, 173, 174]  Burkea africana Hook Wild Syringa Bark Mali and Sub-Saharan Africa Antioxidant and radical scavenging activity.Used to treat coughs, colds, stomach obstruction, infusions against gonorrhoea and syphilis. Proanthocyanidins; fisetinidol-(4alpha- >8)-catechin 3-gallate and bis-fisetinidol-(4alpha- >6, 4alpha- >8)-catechin 3-gallate, with smaller amounts of flavan-3-ols (catechin, epicatechin and fisetinidol) [175, 176]  Crotalaria podocarpa DC. Crotalaria Roots South Africa Anti-inflammatory activity.Used for the treatment of sore-eyes and boils.Expectorant. Flavonoids [67, 177]  Cyclopia intermedia  E. Mey. and C. subternata Vog. Honeybush Leaves and stem South Africa Antioxidant activity.Used as tonic for colds, catarrh and tuberculosis. Pinitol, shikimic acid, p-coumaric acid, 4-glucosyltyrosol, epigallocatechin gallate, the isoflavone orobol, the flavanones hesperedin, narirutin and eriocitrin, a glycosylated flavan, the flavones luteolin, 5-deoxyluteolin and scolymoside, the xanthone mangiferin and the flavonol C-6-glucosylkaempferol.Phenolic content: tyrosol and a methoxy analogue, 2-[4-[O-alpha-apiofuranosyl-(1′′→6′)-beta-d-glucopyranosyloxy] phenyl]ethanol, 4-[O-alpha-apiofuranosyl-(1′′→2′)-beta-d-glucopyranosyloxy]benzaldehyde, five glycosylated flavonols, two isoflavones, four flavanones, two isoflavones, and two flavones [19, 21, 178–181]  Eriosema robustum  Twigs Burundi, Ethiopia, Kenya, Rwanda, Tanzania, Uganda, Democratic Republic of Congo and Cameroon Used traditionally for the treatment of coughs in East Africa and skin diseases in Central Africa 2′,3′,5′,5,7-pentahydroxy-3,40-dimethoxyflavone,2′,3,5′,5,7-pentahydroxy-4′-methoxyflavone [182, 183]  Erythrina latissima  E. Mey. Broad-leaved coral tree Stem WoodRoot woodSeeds South AfricaBotswana Antimicrobial activity and weak radical scavenging properties.Purgative. Flavonoids and isoflavonoids.Isoflavones: erylatissin A and B. Flavanone: erylatissin Cand flavonoids andIsoflavone glycosides: 4′-hydroxyisoflavone-7-O-beta-D-glucopyranoside (compound 1); 4′-hydroxyisoflavone-7-O-alpha-L-rhamnosyl (1→6)-beta-D-glucopyranoside (compound 2); and a new compound 4′, 8-dimethoxy isoflavone-7-O-alpha-L-rhamnosyl (1→6) glucopyranoside (8-O-methylretusin-7-O-alpha-L-rhamnosyl (1-6)-beta-D-glucopyranoside) (compound 3) Isoflavonoids: 5,7-dihydroxy-2′,4′,5′-trimethoxyisoflavanone. [67, 184–186]  E. lysistemon  Hutch. Common coral tree; lucky bean tree Bark South Africa Mild antioxidant activity.Used to treat sores, wounds, abscesses and arthritis. Three prenylated flavonoid derivatives; 5,7,4′-trihydroxy-8-(3′′′-methylbut-2′′′-enyl)-6-(2′′-hydroxy-3′′-methylbut-3′′ enyl) isoflavone (isoerysenegalensein E), 5,7,2′-trihydroxy-4′-methoxy-5′-(3′′-methylbut-2′′-enyl) isoflavanone (lysisteisoflavanone), 5, 4′-dihydroxy-6-(3′′′-methylbut-2′′′-enyl)-2′′-hydroxyisopropyl dihydrofurano [4′′,5′′:8,7] isoflavone (isosenegalensin), together with the four known flavonoids abyssinone V-4′-methylether, alpinumisoflavone, wighteone and burttinone [187–190]  Melilotus elegans  Salzm. ex Ser.(syn. M.  abyssinica Baker) Egug, Gugi, Yemen berriElegant sweet clover Leaves Ethiopia Anti-inflammatory properties.Used for asthma, haemorrhoid, wounds, excavated sore, piles, ulcers mouth infection, lacerated wounds,haemorrhoids, bronchial asthma (personalcommunication) Flavonoids: kaempferol [191–194]  Millettia griffoniana  Baill. Not signalized Root-bark andseeds Cameroon Anti-inflammatory activity.Used as an antimalarial. Coumarin: 4-hydroxy-3-(3′,4′-methylenedioxyphenyl)-5,6,7-trimethoxycoumarin, durmillone, odorantin, 7-methoxyebenosin, calopogonium isoflavone B and 7,2′-dimethoxy-4′,5′-methylenedioxy isoflavone maximaisoflavone G (5) and 7-hydroxy-6-methoxy-3′,4′-methylenedioxyisoflavone and new prenylated isoflavonoids griffonianones A, B, C, D and E.Griffonianone D ((7E)-(6′′,7′′-dihydroxy-3′′,7′′-dimethyloct-2′′-enyl)oxy-4′-methoxyisoflavone), an isoflavone. [195–202]  Parkia biglobosa  (Jacq.) Benth African Locust BeanNèrèOjinyi BarkSeeds MaliSudanIvory Coast Anti-inflammatory activity.Used as antiseptic and to treat coughs, chest pain, and wound healing Tocopherol, ascorbic acid (Seeds) [12, 33, 34, 36–39, 43–53, 55, 64, 66–72, 118, 119, 121, 138, 159, 182, 195, 203–235]  Peltophorum africanum Sond. Weeping wttle Root and bark South Africa Antioxidant and antibacterial activitiesUsed to treat diarrhoea, dysentery, sore throat, wounds, back and joint pains, HIV-AIDS, venereal diseases and infertility. Flavonol glycosides and flavonol glucoside gallates [236–238]  Piliostigma thonningii  (Schum.) Milne- Redh Camel’s foot tree, Monkey BreadNiama (Mali).AbefeKalgoOkpoatuOmepa Root, bark, pods, leaves Nigeria, Ethiopia Botswana, Kenya, Namibia, Senegal, South Africa, Sudan, Tanzania, Uganda, Zambia Anti-oxidant and anti-inflammatory properties.Used to treat wounds, chronic ulcers, cough, respiratory disorders and toothache, gum inflammation, arthritis, headache, backache, andantioxidant supplement. Proanthocyanidins epicatechin, catechin trimers and oligomers, flavonoids, polyphenolics,C-methylflavonols (in the leaf extract) [12, 58, 239–245]  Sutherlandia frutescens R.Br. CancerbushPhetola Leaves South Africa Superoxide and hydrogen peroxide scavenging activities.Used as tonic to boost the immune system. Canavanine, pinitol [246–248]  Trigonella foenumgraecum L. Fenugreek Seeds Ethiopia, Morocco Protective effect against Oxidative stress during ischemia-reperfusion.It is hypolipidemic, and is also used to treat boils and to improve appetite. Free phenolics and Vit C. [26–28, 249, 250]  Humiriaceae  Sacoglottis gabonensis Urb. Cherry tree, ozouga Stem-bark West Africa Antioxidant activity. Bergenin [251–254]  Hypoxidaceae  Hypoxis hemerocallidea Fisch. & C.A. Mey. African potato Corms South Africa Antioxidant activity.Used to treat tuberculosis, cancer, bladder disorders, benign prostatic hyperplasia. Rooperol [188, 255–257]  Lamiaceae  Ocimum basilicum L. MükanduBasil Leaves Burkina FasoEthiopia Intermediate antioxidant activity and high antibacterial activity.Used in Ethiopia to treat Conjunctivitis and inKenya to treat colds and stomacheache. Linalool basil oilMethyl chavicol, eugenol, (E)-methyl cinnamate, thymol, linalool [23, 258]  Ocimum gratissimum L. Tea bush, Scent leaf/Nchuanwu.Ujuju okpevuBasil Leaves Popular republic of Congo (ex Brazaville Congo)Eastern Nigeria Antioxidant activityPopular republic of Congo it is used as a laxative, purgative, and to treat snakebite, diabetes, tooth ache, gingivitis. Xanthomicrol, cirsimaritin, rutin, kaempferol 3-O-rutinoside and vicenin-2 were identified as the major flavonoids, whereas luteolin 5-O-glucoside, luteolin 7-O-glucoside, apigenin 7-O-glucoside, vitexin, isovitexin, quercetin 3-O-glucoside and isothymusin were detected as minor constituents. [12, 58, 258–262]  Lauraceae  Cinnamomum zeylanicum Breyne Cinnamon leaf Leaves MadagascarEthiopia Very high antioxidant and high antimicrobial activities.Used to treat diarrhoea, rheumatism, colds and hypertension Cinnamaldehyde, eugenol and eugenyl acetate to be the main constituents of cinnamon oil. [22–24, 263]  Ocotea bullata (Burch.) Baill. Black stinkwoodUnukane (Zulu) Bark South Africa Anti-inflammatory, cyclooxygenase inhibitory activity.Urinary disorders, headaches. Monoterpenoids [188, 264]  Ravensara aromatica Sonn. Nutmeghavozo BarkLeaf Madagascar Low antioxidant and antimicrobial activity.Useful for chronic respiratory conditions, and sometimes helpful in cases of asthma. Essential oils, principally composed of the monoterpene hydrocarbons a-pinene, sabinene, myrcene, limonene, & the azulene: iso-ledene. In barks, estragole (methyl chavicol) but leaves contain b-myrcene, 1,8-cineole, linalool, and carotol. [23, 25, 265]  Malvaceae  Hibiscus sabdariffa L. Red tea,sorelleRosella Flowers NigeriaSouth Africa Antimutagenic activity and free radical scavenging effects on active oxygen speciesUsed against insomnia, colic. Flavonol glucoside hibiscitrinAnthocyanins. Such as cyanidin 3-O-β-D-glucopyranoside, cyanidin 3-O-(2-O-β-D-xylopyranosyl)-β-D-glucopyranoside, delphinidin 3-O-β-D-glucopyranoside and delphinidin 3-O-(2-O-β-D-xylopyranosyl)-β-D-glucopyranoside. [19, 21, 266–269]  Meliaceae  Trichilia roka  Chiov. Soulafinzan Root Tropical Africa Mali Significantly protective against CCl4-induced liver damage and prevented perisinusoidal fibrosis.Used to treat malaria, abdominal pain and dermatitis. Polyphenols [270, 271]  Menispermaceae  Sphenocentrum jollyanum Pierre Akerejuponajo FruitRoot West Africa Anti-inflammatory activity.Used to treat inflammatory-based diseases Furanoditerpenes: columbin, isocolumbin.Flavonoids-rich fraction. [272–274]  Tinospora bakis  Whole plant Sudan Anti-inflammatory activity. To treat headache and rheumatism A diterpenoid furanolactone, columbin [275]  Moraceae  Dorstenia barteri  var. subtriangularis (Engler)M.E.E.Hijman & C.C.Berg Contrayerva Twigs/leaves Cameroon Antioxidant properties account for the anti-inflammatory action of these extractsUsed to treat arthritis, rheumatism, gout, headache and other forms of body pains. Prenylated flavonoids: Three diprenylated chalcones: bartericins A (-)-3-(3,3-dimethylallyl)-5′-(2-hydroxy-3-methylbut-3-enyl)-4,2′,4′-trihydroxychalcone, bartericins B (+)-3-(3,3-dimethylallyl)-4′,5′-[2′′′-(1-hydroxy-1-methylethyl)-dihydrofurano]-4,2′-dihydroxychalcone and bartericins C 3,4-(6′′,6′′-dimethyldihydropyrano)-4′,5′-[2′′′,-(1-hydroxy-1-methylethyl)-dihydrofurano]-2′-hydroxychalcone and also two novel diprenylated chalcones: 3,5′-di-(2-hydroxy-3-methylbut-3-enyl)-4,2′,4′-trihydroxychalcone, 3, 4-(2,2-dimethylpyrano)-3′-(2-hydroxy-3-methylbut-3-enyl)-2′,4′-dihydroxychalcone, 4,2′, 4′-trihydoxy-3′-prenylchalcone and 4,2′,4′-trihydoxy-3, 3′-diprenylchalcone; and 5,7,4′-trihydoxy-8-prenylflavone.Other known compounds such as stipulin, 4-hydroxylonchocarpin, kanzonol B, 3′-(2-Hydroxy-3-methylbut-3-enyl)-5′-(3,3-dimethylallyl)-4,2′,4′-trihydroxychalcone, and dorstenone. [67, 276–281]  D. ciliata Engl. Contrayerva Aerial parts CameroonCentral Africa Antiradical and antioxidant activities.Used as food additive. phenolic compound (6-prenylapigenin)Flavones: (ciliatin A) 5,4′-Dihydroxy-5′′-isopropenyldihydrfuranol[2′′,3′′:7,6]flavone(ciliatin B) 7,4′-Dihydroxy-3′-methoxy-6′′,6′′-dimethyldihydropyranol[2′′,3′′:5,6]. [282–284]  D. convexa De Wild. Contrayerva Twigs andleaves Democratic Republic of the Congo Antioxidant properties account for the anti-inflammatory action of these extracts.Used to treat arthritis, rheumatism, gout, headache and other forms of body pains. Prenylated flavonoids [67, 276, 280]  D. mannii Hook.f. Contrayerva Twigs/leavesAerial parts Central Africa Antioxidant action against copper-induced LDL oxidation, this activity is like the non-prenylated flavonoid quercetin. Also, inhibition of platelet aggregation and influence of cyclooxygenase and lipoxygenase activity.Used to treat rheumatism, stomach disorders.Anti-trichomonal activity. Grenylated and prenylated flavonoids and flavonones:Flavonones: 6,8-diprenyl-5,7,3′4′-tetrahydroxyflavanone, 4-hydroxylonchocarpin, 4-methoxylonchocarpin, 6-prenylchrysoeriol, 6,8-diprenyleriodictyol, gancaonin P and Prenylated flavonoids: 6,8-diprenyleriodictyol, dorsmanin C 7,8-(2,2-Dimethylchromeno)-6-geranyl-3,5,3′,4′-tetrahydroxyflavone and dorsmanin D 6,8-Diprenyl-3,5,7,4′-tetrahydroxy-3′-methoxyflavone,dorsmanins 1, J and 2′′-epimers of dorsmanins F (6,7-(2,2-dimethylpyrano)-8-prenyl-5,3′,4′-trihydroxyflavanone, G (6,7-(2,2-dimethyldihydro-pyrano)-8-prenyl-5,3′,4′-trihydroxflavanone). Also, dorsmanins F and G.Four new prenylated flavanones, named dorsamine F (7,8-[2′′-(1-hydroxy-1-methylethyl)-dihydrofurano]-6-prenyl-5,3′,4′-trihydroxyflavanone), dorsmaine G (6,7-[2′′-(1-hydroxy-1-methylethyl)dihydrofurano]-8-prenyl-5,3′,4′-trihydroxyflavanone) and dorsamine H (6-prenyl-8-(2-hydroxy-3-methylbut-3-enyl)-5,7,3′,4′-tetrahydroxyflavanone). [67, 187, 207, 285–287]  D. poinsettifolia var. angusta Engl. Dingetenga Whole plant Cameroon Antiradical and antioxidant activities.Used to treat infected wounds. Grenylated and prenylated flavonoids. The unusual 4-phenyl-substituted dihydrocoumarin and the rare geranyl-and prenyl-substituted Chalcone. [207, 288, 289]  D. psilurus Welw. Dingetenga Roots Cameroon Central Africa Antiradical and antioxidant activities.Used against snakebite and to treat rheumatism, headache and stomach disorders. Grenylated and prenylated flavonoids.Three phenolic compounds: 6,8-diprenyl-3′ [O],4′-(2,2-dimethylpyrano)-3,5,7-trihydroxyflavone, 3,6-diprenyl-8-(2-hydroxy-3-methylbut-3-enyl)-5,7,2′,4′-tetrahydroxyflavone and an unusualB/C ring modified flavonoid derivative for which the names dorsilurins C, D and E, respectively, are proposed.Two new flavones, dorsilurins A and B, and a new benzofuran derivative have been isolated from Dorstenia psilurus, together with three known phenylpropanoid derivatives, stearyl-p-coumarate [octadecanyl 3-(4-hydroxyphenyl)prop-2-enoate], stearyl ferulate [octadecanyl 3-(4-hydroxy-3-methoxyphenyl)prop-2-enoate] and psoralen. [206, 282, 290–292]  Myrtaceae  Eugenia elliptica Sm.  Syzygium smithii (Poir.)  Nied. Lilly Pilly Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), quercetin-3-O-glucoside (isoquercitrin), (+)-catech [293, 294]  E. fasciculata Wall. Not signalized Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), quercetin-3-O-glucoside (isoquercitrin), (+)-catech.procyanidin B2 dimer and (-)-epicatechin [293]  E. orbiculata Lam. Not signalized Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), quercetin-3-O-glucoside (isoquercitrin), (+)-catech.quercetin-3-O-rutinoside (rutin), [293, 295]  E. pollicina  J.Gueho & A.J.Scott Not signalized Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), quercetin-3-O-glucoside (isoquercitrin), (+)-catech.(-)-epicatechin gallate [293, 296]  Monimiastrum acutisepalum  J. Gueho & A.J. Scott. Not signalized Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), and quercetin-3-O-glucoside (isoquercitrin).(+)-catechin [293–295]  M. globosum  J.Gueho & A.J.Scott Not signalized Leaves Mauritius Modulate the expression of the antioxidant enzyme genes. Quercetin-3-O-galactoside (hyperoside), kaempferol-3-glucoside (astragalin), and quercetin-3-O-glucoside (isoquercitrin).(-)-epicatechin gallate [293]  Syzygium aromaticum (L.)  Merr. & L.M.Perry Clove bud Dried flowersBuds MadagascarSudan Antioxidant and antimicrobial activities.Used to treat tooth ache and throat inflammation. EugenolMethyleugenol [23, 297, 298]  S. coriaceum  J.Bosser & J.Guého Bois de pomme  Mauritius Abilities to modulate the expression of the antioxidant enzyme genes. Phenols and flavonoids: Quercetin-3-O-rutinoside, kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), (+)-catechin, procyanidin B1 dimer, (-)-epicatechin gallate [293]  S. glomeratum DC. Bois de pomme Leaves Mauritius Abilities to modulate the expression of the antioxidant enzyme genes.Used to treat boils, abscesses, fever and wounds and as expectorant. Phenols and flavonoids: kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), procyanidin B1 dimer, (-)-epicatechin gallate, chlorogenic acid, (-)-epicatechin [293]  S. guehoii Not signalized  Mauritius Abilities to modulate the expression of the antioxidant enzyme genes. Phenols and flavonoids: quercetin-3-O-rutinoside (rutin), kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), (+)-catechin, chlorogenic acid, procyanidin B2 dimer [293]  S. mauritianum  J.Gueho & A.J.Scott Not signalized Leaves Mauritius Abilities to modulate the expression of the antioxidant enzyme genes. Phenols and flavonoids: quercetin-3-O-rutinoside (rutin), kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), (+)-catechin, chlorogenic acid [293]  S. petrinense  J.Bosser & J.Guého Not signalized  Mauritius Abilities to modulate the expression of the antioxidant enzyme genes. Phenols and flavonoids: quercetin-3-O-rutinoside (rutin), kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), procyanidin B1 dimer, chlorogenic acid [293]  S. venosum (Lam.)  J.Gueho & A.J.Scott Not signalized  Mauritius Abilities to modulate the expression of the antioxidant enzyme genes. Phenols and flavonoids: quercetin-3-O-rutinoside (rutin), kaempferol-3-glucoside (astragalin) and quercetin-3-O-glucoside (isoquercitrin), (+)-catechin, procyanidin B2 dimer [293, 295, 299]  Oleaceae  Olea europaea  subsp africana (Mill.)P.S. Green African wild olive Leaves South Africa Potent antioxidant activity.Used as eye lotions and tonics, lower blood pressure, improve kidney function and deal with sore throats. The early Cape settlers used the fruits to treat diarrhoea Oleuafricein (mixture of oleanolic acid and ursolic acids), Triterpenoids and oleoropein. [84, 300, 301]  Pedaliaceae  Harpagophytum procumbens DC.ex Meissner Devil’s claw Root South AfricaNative to the Kalahari Desert of southern Africa, Namibia andBotswana. Anti-inflammatory and ability to inhibit the expression of cyclooxygenase-2 and inducible nitric oxide by suppression of NF-kappaB activation.Used for pain, muscular tension, osteoarthritis, degenerative rheumatism or painful arthrosis and tendonitis as well as tonic for loss of appetite and dyspeptic complaints. Roots contain iridoid glycosides mainly harpagoside.Other constituents are flavones and flavonols kaempferol, and luteolin. [302–312]  Piperaceae  Piper guineense  Schum. & Thonn. West African black pepperBush pepperIkom, Amanakakwale iyeyeh ashoesietaquale Meshoro Fruit, seed and leaf Ghana, West AfricaNigeriaCameroon Antioxidant activity. Volatile oil components-monoterpenes, sesquiterpenes, terpenoids, lignans and sterols. [313–316]  Podocarpaceae  Podocarpus speciesPodocarpus  elongates   Podocarpus  falcatus,  Podocarpus henkelii  and Podocarpus latifolius  Leaves and young stems Eastern and Southern Africa These species are used to treat fevers, asthma, coughs, cholera, chest complaints, arthritis, rheumatism, painful joints and venereal diseases Diterpenoids, bioflavonoids and Totarol [317]  Ranunculaceae  Nigella sativa L. Black cumin Seed African countries in the Mediterranean region Antioxidant potentials through scavenging ability of different free radicals including the superoxide anion radical, inhibition of lipid peroxidation, and protection of liver against carbon tetrachloride (CCl4)-induced liver fibrosis in rabbitsUsed to treat diarrhoea, asthma, and as gastroprotective agent. Oil: Thymoquinone [29–31, 318, 319]  Rosaceae  Crataegus monogyna Jacq. Hawthorn, May Blossom, May Day Flower, White Thorn. Fresh vegetative and reproductive organs Mauritius, Northern Africa Antioxidant activities.Used for its neuro- and cardiosedative actions. Polyphenols: (proanthocyanidin, flavonoid, anthocyanin, (-)-epicatechin, procyanidin B2, chlorogenic acid).Flavonoids:quercetin and quercetrin, glycosides, proanthocyanidins, anthocynaidins, saponins, tannins, and crateteginAlso, Vitamin C. [320–323]  Leucosidea sericea  Leaf, bark and roots Southern Africa Antimicrobial and anti-inflammatory properties Phenolics, alkaloids and saponins [210]  Pygeum africanum Hook. f. African plum treeRed Stinkwood Bark South Africa Anti-inflammatory.Used to treat against benign prostatic hyperplasia, prostatitis 14% triterpenes (urolic acids, oleanolic acid, crataegolic acid), 0.5% n-docosanolPhytosterol (β-sitosterol, β-sitosterone, Campesterol [188, 324–327]  Rubiaceae  Crossopteryx febrifuga Benth. Roger Blench“rima jogoo-hi/je” SeedsLeaf and roots MaliNigeria Radical scavenging and lipoxygenase inhibition activities.Used to treat fever and various respiratory diseases Flavonoids [328–330]  Rutaceae  Agathosma betulina (Berg.) Pillans. Round-leaf buchu Leaves,stems South Africa Hydroxyl radical ion scavenging ability.Used for stomach problems, kidney and urinary track diseases. Essential oils and flavonoids [188, 331, 332]  A. crenulata(L.)  Pillans Oval-leaf buchu Leaves,stems South Africa Anti-inflammatory activity.Used to treat benign prostatic hyperplasia, prostatitis, diabetes, inflammation of the colon, gums, and mucous membranes. Leaves chewed to relieve stomach complaints. Essential oils and flavonoids [84, 188, 331, 332]  Fagara zanthoxyloides Lam. xeti, xeWô Roots, root-bark Cameroon, Uganda Antioxidant activity.Used to treat gingivitis, toothache, urinary and venereal diseases, rheumatism and lumbago, malaria and other infections. Phenylethanoid derivative, lignans and fagaronine [333–336]  Sapindaceae  Dodonaea viscosa  Jacq.  Synonyms: Dodonaea angustifolia L. f.;Ptelea viscosa L. Umusasa Leaves Rwanda Anti-inflammatory activity by inhibiting the synthesis of prostaglandin (PG) E(2).Used to treat rheumatism, skin infections, diarrhea, stomachaches, pains of hepatic and splenic origin, uterine colic. It is also used as an antipruritic in skin rashes and for the treatment of some throat, dermatitis and hemorrhoids. Quercetin, isorhamnetin [337–341]  Xanthorrhoeaceae  Aloe ferox Mill. Bitter aloe or Cape aloe Leaves South Africa, Lesotho A. ferox gel contains at least 130 medicinal agents with anti-inflammatory, analgesic, calming, antiseptic, antiviral, antiparasitic and anticancer effects Chromones, anthraquinones, anthrone, anthrone-C-glycosides, and other phenolic compoundsBarbaloin [9]  Zingiberaceae  Siphonochilus aethiopicus (Schweinf.) B.L. Burtt. Wild gingerNatal gingerAfrican Ginger Rhizome South Africa Anti-inflammatory activity through cyclooxygenase inhibitory (prostaglandin-synthetase inhibition), activity.Used to treat Coughs, colds, asthma. Sesquiterpenoid [188, 264, 342]Table 2
Medicinal plants with confirmed antioxidant activity or medicinal plants that contain compounds that are not known to have antioxidant activity.
Family and plant name Vernacular name Plant part Country/area Medicinal use and/or experimental validation Compounds isolated Reference Acanthaceae  Barleria species B. albostellata, B. greenii,  B. prionitis  Leaves, twigs and roots South Africa Anti-inflammatory and antioxidant activities Not identified [212, 213]  Hypoestes rosea Decne. Not signalized Leaf extract Nigeria Anti-inflammatory activity due in part to its ability to inhibit NF-kappaB activation through direct inhibition of IkappaB kinase (IKK). Diterpene: Hypoestoxide (a bicyclo [9,3,1] pentadecane) [380, 381]  Aizoaceae  Glinus lotoidesL. “Mettere”Hairy carpet -weed Seeds CameroonEthiopia, Sudan, Uganda, Egypt. Used to treat cardiovascular and gastrointestinal system. Three flavonoids: apigenin-7-O-glucoside, isovitexin, and luteolin-7-O-glucosideThree isoflavonoids:5,7,2′,4′-tetrahydroxy-6-(3,3-dimethylallyl)isoflavone,5,7,4′-trihydroxy -6,3′-di-(3,3-dimethylallyl)isoflavone, and 5,7,2′,4′-tetrahydroxy-6,3′-di-(3,3-dimethylallyl) isoflavone. [290, 382–386]  G. oppositifolius(L.) Aug. DC. Balasa Whole plant Mali Antioxidant and radical scavenging abilities. kaempferol 3-O-galactopyranoside [387, 388]  Aloaceae  Aloe claviflora Burch. Kraal aloe  South Africa Free radical scavenging and moderate inhibition in lipid peroxidation.Used as a purgative. Not identified [35]  A. maculata  Forssk.(=A. saponaria) “Yellow Form”Tiger Aloe, Soap Aloe  South Africa Free radical scavenging and moderate inhibition in lipid peroxidation.Used as a purgative. Not identified [35]  A. thraskiiBaker Dune aloe  South Africa Free radical scavenging and moderate inhibition in lipid peroxidation.Used as a purgative. Not identified [35]  Anacardiaceae  Sclerocarya birrea(A.Rich.) Hochst Marula Stem-bark  Anti-inflammatory activity.Used to treat diabetes, tonsillitis, snake bite and also diarrhoea. Not identified [389]  Annonaceae  Enantia chlorantha Oliver Erenbavbogo, Mföl Muamba Root, stem-bark Nigeria Anti-inflammatory activity.Used to treat ulcers and leprous spots wounds. Bark sap is taken as decoction against diarrhoea. Not identified [390–393]  Uvaria afzelii Sc. Elliot Pareho-houon, Bahie oulin Leaves, roots and stem-bark Ivory Coast Used as for its antiparasitic activity Anthocyanins and other flavonoids [394–396]  U. chamae P.Beauv. OkandiiAnweda tsoGa Stem, barkLeaves, root Ivory Coast Nigeria Used for its antiplasmodial activity. Polyphenols [12, 397, 398]  Apocynaceae  Picralima nitida Th. & H. Dur. Ghana: Kpetepetetso, Kanwini,KanwinuCameroon: motoko-toko Seeds Stem-bark Ghana Anti-inflammatory activity.Used for its analgesic and anti-inflammatory properties. Not identified [168, 399–402]  Rauvolfia vomitoria Afzel. Asofeyeje, adapopoMwanje Root-bark Ghana Anti-inflammatory activity.Used for its analgesic, antipyretic and anti-inflammatory activities. Also to treat scabies, high blood pressure, fever and snakebites. Not identified [56]  Araliaceae  Cussonia barteri Seem. Cabbage tree LeavesRoots Nigeria, Mali Antioxidant and radical scavenging abilities. Inhibitory activity on 5-lipoxygenase and cyclooxygenase-1. Not identified [357, 403]  Arecaceae  Hyphaene thebaica Mart. Not signalized Shell Niger Antioxidant activity Not identified [11]  Asclepiadaceae  Calotropis procera(Aiton)W.T.Aiton African milk weedSodom apple/Giant milkweed/ Latex Ethiopia Anti-inflammatory and antioxidant activities. Not identified [404] Swallow-wort/Auricula tree. Sudan Used to control dermal fungal infections and for pain relief. Latex used against scorpion stings and roots for jaundice.  Gongronema latifolium Benth. Not signalized Leaves Nigeria Antioxidant activity Not identified [405–407]  Leptadenia hastata Decne. Not signalized Leaves Niger Antioxidant activity Not identified [11]  Pachycarpus rigidus E. Mey. Not signalized Bark South Africa Antioxidant activity.Used to treat pain in the joints Not identified [188]  Asparagaceae  Asparagus virgatus BakerRefug. Bot. (Saunders) Broom asparagus Bark South Africa Antioxidant activity.Used to treat syphilis, anthelmintic Not identified [35]  Asteraceae  Ageratum conyzoides L. InkurubaHerbe à bouc Whole plant Central Africa, Rwanda Ethiopia Antioxidant and anti-inflammatory properties.Used to treat mastitis and urogenital infections and to dress wounds. Also as a gastroprotective. Not identified [12, 408, 409]  Artemisia herba-alba Desert wormwood, shih Aerial parts Algeria, Tunisia, Israel, Morocco Herbal tea fromA. herba-albahas been used as analgesic, antibacterial, antispasmodic, and hemostatic agents in folk medicines Camphor (17–33%),α-thujone (7–28%), and chrysanthenone (4–19%) [9]  Artemisia judaica L. Wormwood Leaves Egypt Used for gastrointestinal disorders Flavonoids with antioxidant activities. [410]  Callilepis laureola  DC. Ox-eye daisy, Impila Tuber South Africa Antioxidant and radical scavenging activities.Used to induce fertility, impotence, tapeworm infestations but induces hepatic and renal tubular necrosis. Not identified [188, 411, 412]  Psiadia punctulata (DC) Vatke Mwendathigo Leaf exudate Kenya, East Africa Used to treat colds, fevers and abdominals pains. Flavones: 5,7-dihydroxy-2′,3′,4′,5′-tetramethoxyflavone, 5,4′-dihydroxy-7,2′,3′,5′-tetramethoxyflavone, 5,7,4′-trihydroxy-2′,3′,5′-trimethoxyflavone, 5-hydroxy-7,2′,3′,4′,5′-pentamethoxyflavone and 5,7,3′-trihydroxy-2′,4′,5′-trimethoxyflavone. [359, 413]  Vernonia kotschyana Sch. Bip. ex Walp. Buaye Leaves, roots Mali Anti-inflammatory activity.Used to treat gastritis, gastro duodenal ulcers, as an aid to ameliorate digestion and as a wound healing remedy. Immunomodulating activities. Not identified [187, 414]  Bignoniaceae  Kigelia pinnata DC. Suasage tree,Cucumber tree Rootfruit Egypt Used as dressing for ulcers and used to treat rheumatismAnti-inflammatory activity Naphthoquinones: kigelinone, isopinnatal, dehydro-alpha-lapachone, and lapachol and the phenylpropanoids: p-coumaric acid, ferulic acid (root), kigelinone and caffeic acid (fruits). [415, 416]  Tabebuia rosea (Bertol.) DC. Pink tecomaPink trumpet tree LeavesStem-bark Nigeria Used to treat arthritis. Tannins, flavonoids, alkaloids, quinones and traces of saponins [107]  Crescentia cujete L. CalabashGourd tree LeavesStem-bark Nigeria Used as purgative and to treat coughs. Tannins, flavonoids, alkaloids, quinones and traces of saponins [107]  Bombacaceae  Bombax costatum Pellegrin & Vuillet Not signalized Fruit Niger Antioxidant activity Not identified [11]  Boraginaceae  Heliotropium  indicumL. Nonsikou Leaves Mali Moderate antioxidant activity.Used for wound healing and for ocular infection. Not identified [417–419]  Buddlejaceae  Buddleja  madagascariensis Lam. Butterfly-bush Leaves Egypt Used to treat coughs, asthma, and bronchitis. Flavonoids triglycosides: hesperetin and diosmetin 7-O (2′′,6′′- di-O-alpha-L-rhamnopyranosyl)-beta-D-glucopyranosides [420]  Caesalpiniaceae  Cassia fistula L. Golden shower tree Fruit Mauritius Laxative. Phenolics and flavonoids [368]  Canellaceae  Warburgia salutaris (Bertol F.) Chiov. Pepper-bark treeIsibaha Bark South Africa Antioxidant and radical scavenging activities.Used to treat coughs, stomach ulcers, malaria, rheumatism, liver and venereal diseases Not identified [188]  W. ugandensisSprague Fever tree Stem-barkLeaves KenyaEthiopia Used to treat stomach ache, chest pains, malaria, toothache and coughs. Flavonol glycoside Kaempferol, kaempferol 3-rhamnoside, kaempferol3-Rhamnoside-7,4′-digalactoside and Quercetin: 3-Rhamnosyl(1→6[glucosyl(1→2)glucoside]-7-rhamnoside, kaempferide 3-O-beta-xylosyl (1→2)-beta-glucoside, kaempferol 3-O-alpha-rhamnoside-7,4′-di-O-beta-galactoside, kaempferol 3,7,4′-tri-O-beta-glucoside, kaempferol 3-rutinoside, myricetin, quercetin 3-rhamnoside, kaempferol 3-arabinoside, quercetin 3-glucoside, quercetin, kaempferol 3-rhamnoside-4′-galactoside, myricetin 3-galactoside and kaempferol 3-glucoside. [421–424]  Capparaceae  Boscia senegalensis (Pers.) Lam. ex Poiret Senegal Boscia Fruit hullRoots and leaf MaliNiger Antioxidant activity.Used to treat diarrhoea, cholera, tachycardia, pectoral pain. Not identified [12]  Gynandropsis gynandra Merr. Not signalized Leaves Niger Antioxidant activity Not identified [11]  Celastraceae  Salacia leptoclada Tul. Lemon rope Root South Africa Antioxidant activity.Used as an aphrodisiac. Not identified [188]  Chenopodiaceae  Salsola somalensisN.E.Br. Dingetegna Roots Ethiopia Used as taenicide. Nine new isoflavones, 5,3′-dihydroxy-6,7,2′-trimethoxy isoflavone, 5,8,3′-trihydroxy-7,2′-dimethoxyisoflavone, 8,3′-dihydroxy-5,7,2′-trimethoxyisoflavone, 5,6,3′-trihydroxy-7,2′-dimethoxyisoflavone, 6,7,3′ -trihydroxy-5,2′-dimethoxyisoflavone, 5,8,3′-trihydroxy -2′-methoxy-6,7-methylenedioxyisoflavone, or 5,6,3′-trihydroxy-2′-methoxy-7,8-methylenedioxyisoflavone, 3′-hydroxy-5,6,7,2′-tetramethoxyisoflavone, 7,3′-dihydroxy -5,6,2′-trimethoxyisoflavone and 6,3′-dihydroxy-5,7,2′-trimethoxyisoflavone. [425]  Clusiaceae  Psorospermum guineense Hochr. Karidjakouma Leaves Mali Antioxidant activity.Used as diuretic and febrifuge. Not identified  Combretaceae  Pteleopsis suberosa Engl. & Diels. Girga Stem-bark Mali Antioxidant properties.Used to treat gastric and duodenal ulcers. Not identified [329, 426]  Dioscoreaceae  Dioscorea dumetorum Th.Dur.et Schinz Cluster yamAfrican bitter yamTrifoliate yam Tubers NigeriaTropical West Africa Antioxidant and hypolipidemic activities.Used to treat diabetes. Not identified [152, 153, 427]  Ebenaceae  Diospyros abyssinica (Hiern) F. White Giant diospyros Leaves, rootsRoot-bark Mali Radical scavengers and lipoxygenase inhibitors. Not identified [357]  Euclea divinorumHiern Diamond-leaved eucleaMagic guarri Roots Ethiopia Used to treat venereal diseases, chest pains, pneumonia, internal body pains, stomach-ache and diarrhea. Chewed roots ease toothache. Flavonoids [428]  Euphorbiaceae  Acalypha hispida Burm. f. Chenille plantRed-hot cattail LeavesFlowers Nigeria Used as anti-bacterial agent. Gallic acid and Quercetin 3-O-rutinoside and kaempferol 3-O-rutinosideThe main anthocyanin is the known cyanidind 3-O-(2-O-galloylgalactose, but a minor pigment (5%) is the new cyanidin Cy 3-O-(2-O-galloyl-6-O-rhamnosylgalactoside [228, 429]  A. wilkesiana  Müll. Arg. Copper leaf Leaves Nigeria Used to treat ailments of microbial origin Gallic acid and Quercetin 3-O-rutinoside and kaempferol 3-O-rutinoside [430]  Croton gratissimus Burch. Lavender fever-berry Bark South Africa Used as purgative for abdominal disorders, fever. The charred and powdered bark is used to treat bleeding gums Flavonoids. [188]  Euphorbia hirta L. KasandasandaUfu idire Whole plantLeaves Ethiopia Used to treat diarrhoea and asthma. Flavonoid: quercitrinFlavonol: Euphorbianin (3-(6′′′-Acetylglucosyl) (1→3)galactoside) [12, 431–433]  Fabaceae  Acacia caffra (Thunb.) Wild. Hook-thornCat-thorn Bark South Africa Used to treat diarrhoea and as emetics. Proanthocyanidins: oritin-(4alpha→5)-epioritin-4beta-ol, ent-epioritin-(4alpha→5)-epioritin-4beta-ol and epioritin-(4beta→5)-epioritin-4alpha-ol and ent-oritin-(4beta→5)-epioritin-4alpha-ol. [434–436]  A. galpinii Burtt Davy. Monkey-thorn Bark South Africa Used to treat diarrhoea. Proanthocyanidins: oritin-(4alpha→5)-epioritin-4beta-ol, ent-epioritin-(4alpha→5)-epioritin-4beta-ol and epioritin-(4beta→5)-epioritin-4alpha-ol and ent-oritin-(4beta→5)-epioritin-4alpha-ol. [434, 435]  Afzelia bella  Harms Pretty Afzelia Stem-bark Ivory Coast Used to treat skin diseases and cough. An acylated dihydroflavonol glycoside identified as 2R,3R-trans-aromadendrin-7-O-beta-D-glucopyranoside-6′′-(4′′-hydroxy-2′′-m ethylene flavonoids:butanoate), along with five known flavonoids and the lignan glycoside (+)-isolariciresinol 9-O-xyloside. [437]  Bolusanthus speciosus  Harms Tree Wisteria RootStem-bark South Africa, Botswana, Mozambique, Zimbabwe, Zambia. Used to treat abdominal pains, emetism and tuberculosis. Three new flavonoids from the root: 5,7,4′-trihydroxy-6-[1-hydroxy-2-methylbuten-2-yl]isoflavone (isogancaonin C), 7,2′-dihydroxy-4′-methoxyisoflav-3-ene (bolusanthin III), 6,6′-dihydroxy-4′-methoxy-2-arylbenzofuran (bolusanthin IV) in addition to eight known derrone, medicarpan, genistein, wighteone, lupiwighteone, gancaonin C, 7-hydroxy-4′-methoxyisoflavone and 7,3′-dihydroxy-4′-methoxyisoflavone flavonoids2R,3R-Aromadendrin 7-(6-[4-hydroxy-2-methylenebutanoyl]glucoside).Two new isoflavonoids from the combined ethyl acetate/methanolic extracts of the stem bark of Bolusanthus speciosus have been established as 4,7,2′-trihydroxy-4′methoxyisoflavanol (1) and 5,7,3′,4′-tetrahydroxy-5′-(2-epoxy-3-methylbutyl)isoflavanone (2). Five other known isoflavonoids, 5,7,3′-trihydroxy-4′-methoxy-5′-γ, γ-dimethylallyisoflavanone, 5,7,2′trihydroxy-4′-methoxy-6,5′-di(γ, γ-dimethyla)isoflavanone, 5,7,2′,4′-tetrahydroxy-8,5′-di(γ, γ-dimethylallyl)isoflavanone, 5,7,2′,4′-tetrahydroxy-8,3′-di(γ, γ-dimethylallyl)-isoflavanone, and derrone. [67, 358, 438]  Crotalaria lanceolata E. Mey. Lanceleaf rattlebox Root South Africa Antioxidant activity.Used to treat coughs. Not identified [188]  Derris trifoliataLour. Common derris Root-bark.Stem-bark. Seeds. Kenya Used for prevention of cancer.Entire plant is used as stimulant, antispasmodic. Bark is used as an alternative in rheumatism. An isoflavonoid derivative, named 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isoflavonoids (the sub-class is here named as rotenoloid). In addition, the known rotenoids, rotenone, deguelin and alpha-toxicarol. In addition, two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone).In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified. Also one new rotenoid, 6-alpha,12-alpha-12a-hydroxyelliptone. [438–441]  Entada africana Guill. & Perr. Samanere Leaves MaliNiger Antioxidant properties.Protective against carbon tetrachloride-induced liver damage.Used to treat fever and various respiratory diseases. Not identified [329, 357, 442, 443]  Erythrina abyssinica Lam. Red hot poker tree Stem barkRoot bark Kenya Used to treat malaria. New isoflav-3-ene [7,4′-dihydroxy-2′,5′-dimethoxyisoflav-3-ene] in addition to the known compounds erycristagallin, licoagrochalcone A, octacosyl ferulate and triacontyl 4-hydroxycinnamate were identified. A new chalcone, 2′,3,4,4′-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4′,7-dihydroxy-3′-methoxy-5′-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids [444, 445]  E. burttii Baker f. Not signalized Stem-barkRoot-bark Kenya Used as antifungal and antibacterial agent. Two new flavanones: 5,7-dihydroxy-4′-methoxy-3′,5′-di-(3-methylbut-2-enyl)flavanone (trivial name, abyssinone V-4′-methyl ether) and 5,7-dihydroxy-4′-methoxy-3′-(3-hydroxy-3-methylbut-1-enyl)-5′-(3-methylbut-2-enyl)favanone (trivial name, burttinone). A new isoflavone, 5,2′,4′-trihydroxy-7-methoxy-6-(3-methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4′-methoxy-3′-(3-methylbutadienyl)-5′-(3-methylbut-2-enyl)flavanone, 3 isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein)Three isoflav-3-enes, 7,4′-dihydroxy-2′-methoxy-6-(1′′,1′′-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4′-hydroxy-2′-methoxy-2′′,2′′-dimethylpyrano[5′′,6′′:8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4′-dihydroxy-2′-methoxy-8-(3′′,3′′-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and 2-arylbenzofuran, 6,4′-dihydroxy-2′-methoxy-5-(1′′,1′′-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D). [446–449]  E. eriotricha Harms. Not signalized Root-bark Cameroon Anti-microbial activity A novel isoflavanone, named eriotrichin B, one new prenylated flavanone, named sigmoidin L, one flavanone (sigmoidin A), four isoflavones (scandenone, 6,8-diprenylgenistein), flemiphilippinin B and 8-prenyldaidzein [450, 451]  E. sacleuxii Hua Kinyarwanda Bark Kenya Used to treat fever, malaria and leprosy. Two new isoflavanones, (R)-5,7-dihydroxy-2′,4′,5′-trimethoxyisoflavanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy-2′,4′,5′-trimethoxy-2′′,2′′-dimethylpyrano[5′′,6′′:6,7]isoflavan one (trivial name, (R)-saclenone) [452, 453]  Millettia ferruginea  (Hochst.) Baker BirbiraSotalloSari Bark Ethiopia Used for skin disorders. O-Geranylated and O-prenylated flavonoids, C-prenylated isoflavonesGeranylated and prenylated flavonoids [199]  M. duraDunn. Runyankore Uumuyogoro Stem-bark RwandaUganda Used for blood parasitism Flavonoids: A new isoflavone (7,3′-dimethoxy-4′,5′-methylenedioxyisoflavone) and three known isoflavones [isoerythrinin A 4′-(3-methylbut-2-enyl) ether, isojamaicin and nordurlettone]. [454, 455]  Ostryoderris stuhlmannii(Taub.) Dunn ex Harms Mnyinga Leaves Mali Antioxidant activity.Used to treat painful menstruation, peritonitis, gastritis, colitis and gingivitis. Not identified [357]  Piliostigma reticulatum(DC.) Hochst Kalga LeavesBark Nigeria High antioxidant activity.Used to treat wounds, bronchitis, malaria, sterility (leaves) and diarrhoea and dysentery (bark). Not identified [240]  Sesbania pachycarpa DC. Not signalized Leaves Niger Antioxidant activity Not identified [11]  Tephrosia polyphylla (Chiov.) J.B. Gillett Hoary pea Aerial part Kenya  Flavonoids [456]  T. deflexa Baker Hoary pea Aerial part Senegal  Flavonoids: Rutin 1 – quercetine 3-O-a-L-rhamnopyrannosyl (1-6) glucopyrannose – and morin 2 – 3,5,7,2′,4′-pentahydroxyflavone. [457]  T. albifoliolis  A.Nongonierma & T.Sarr Hoary pea Aerial part Senegal  Flavonoids: Rutin 1 – quercetine 3-O-a-L-rhamnopyrannosyl (1-6) glucopyrannose – and morin 2 – 3,5,7,2′,4′-pentahydroxyflavone. [457]  Taverniera abyssinicaA.Rich. Dingetegna Root Ethiopia Used to treat fever, discomfort and pain, stomach ache. Four isoflavonoids [290, 458, 459]  Flacourtiaceae  Flacourtia flavescens Willd. Not signalized Leaves Mali Antioxidant activity. Not identified [357]  Geraniaceae  Pelargonium reniforme Spreng. Xhosa (Umckaloabo) Root Southern Africa Used to treat liver disorders, laxative, purgative, cancer, and pulmonary disorders Polyphenols: catechol (3′4′-dihydroxy) element in the B-ring, which possesses higher antioxidant activity than ascorbic acid. [362, 460, 461]  Gunneraceae  Gunnera perpensa L. River pumpkinUgobho RootLeaves and stem. South Africa Decreased lucigenin enhanced chemiluminescence.Used to treat wounds and psoriasis. Not identified [21, 462]  Irvingiaceae  Irvingia gabonensis(Aubry-Lecomte ex O’Rorke) Baill. Bush mangoOno Seeds NigeriaCameroon Antioxidant activity.Used as laxative and for stomach and kidney pain. Shown to lower total cholesterol. Not identified [12, 313, 463]  Lamiaceae  Leonotis leonurus (L.)R.Br. Wild dagga Leaves South Africa Anti-inflammatory properties.Used to treat headaches, dysentery, coughs and colds. Not identified [13]  Salvia stenophyllaBurch. ex Benth. Sage Leaves South Africa Solvent extracts: antioxidant activity but poor anti-inflammatory properties.Essential oils: anti-inflammatory activity but poor anti-oxidant activity.Used against fever and digestive disorders. Not identified [360]  S. repensBurch.ex Benth. Not signalized Leaves South Africa Solvent extracts: antioxidant activity but poor anti-inflammatory properties.Essential oils: anti-inflammatory activity but poor anti-oxidant activity.Used for fevers and digestive disorders. Not identified [360]  S. runcinataL.f. Not signalized Leaves South Africa Solvent extracts: antioxidant activity but poor anti-inflammatory properties.Essential oils: anti-inflammatory activity but poor anti-oxidant activity.Used against fever and digestive disorders. Not identified [360]  Loranthaceae  Tapinanthus globiferus Tiegh. Not signalized Leaves Niger Antioxidant activity Not identified [11]  Malvacea  Adansonia digitata(L.) English: baobab, Afrikaans: kremetart, Hausa: kuka, Sotho: seboi, Tswana: mowana, Tsonga: shimuwu, Venda: muvhuyu, Arabic: tabladi Leaves, root, bark and fruits All over Africa, but limited trees in Central Africa Antioxidant, analgesic and anti-inflammatory properties of extracts L-ascorbic acid [36, 464]  Mimosaceae  Albizia lebbeck (L.) Benth. East Indian walnut, frywood, koko, lebbek, lebbek tree, rain tree, raom tree, silver raintree, siris rain tree, siris tree, soros-tree, woman’s tongue. Leaves and bark Egypt Used to treat asthma and skin disorders (bark) and eye diseases and dysentery (leaves) Two new tri-O-glycoside flavonols: kaempferol and quercetin 3-O-alpha-rhamnopyranosyl(1→6)-beta-glucopyranosyl(1→6)-beta- galactopyranosides [465]  Moraceae  Dorstenia angusticornis Engl. Not signalized Twigs Cameroon Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. Two noveldiprenylated chalcones: 3,5′-di-(2-hydroxy-3-methylbut-3-enyl)-4,2′,4′-trihydroxychalcone, 3, 4-(2,2-dimethylpyrano)-3′-(2-hydroxy-3-methylbut-3-enyl)-2′,4′-dihydroxych alcone and the known stipulin.3-(2-Hydroxy-3-methylbut-3-enyl)-5′-(3,3-dimethylallyl)-4,2′,4′-trihydroxy chalcone and the known compounds: gancaonin Q, paratocarpins C, F, and lupeol. [67, 278]  D. dinklagei Engl. Not signalized Twigs Cameroon Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. Three prenylated flavonoids, dinklagins A, B and C identified, respectively, as(dinklagin B): (+)-5,4′,5′′ξ-Trihydroxy-6′′,6′′-dimethyldihydropyranol[2′′,3′′:7,6]flavone.(dinklagin C): (+)-6-(2ξ-Hydroxy-3-methyl-3-butenyl)-5,7,4′-trihydroxyflavone(-)-6-(3,3-dimethylallyl)-7-hydroxy-6′′′, 6′′′-dimethylchromeno-(4′,3′,2′′′,3′′′)-flavanone, (+)-5,4′,5′′ξ-trihydroxy-6′′,6′′-dimethylchromano-(7,6,2′′,3′′)-flavone and (+)6-(2ξ-hydroxy-3-methyl-3-butenyl)-5,7,4′-trihydroxyflavone.6-prenylapigenin, 4-hydroxylonchocarpin, stipulin and 5,4′-dihydroxy-6′′,6′′-dimethylchromano-(7,6,2′′,3′′)-flavone. [67, 226]  D. elliptica Bur. Not signalized Twigs Botswana Used to treat eye infection. Monoprenylated flavan [466]  D. Kameruniana. Engl. Not signalized Leaves Botswana Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. Two novel favonoids: 6,7-(2,2-dimethylchromano)-5,4′-dihydroxyfavone and 3,4-,4′,5′-bis-(2,2-dimethylchromano)-2′-hydroxychalcone together with the known 6-(3-methylbut-2-enyl)apigenin and two chalcones (E)-1-[2,4-dihydroxy-3-[3-methylbut-2-enyl]phenyl]-3-[4-hydroxyphenyl]-prop-2-en-1-one and (E)1-[2,4-dihydroxy-5-[3-methylbut-2-enyl]phenyl]-3-[4-hydroxy-3-[3-methylbut-2-enyl]phenyl]-prop-2-en-1-one. [467]  D. prorepens Engl. Not signalized Twigs Botswana Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. Digeranylated chalcone, 5,3′-(3,7-dimethyl-2,6-octadienyl)-3,4, 2′,4′-tetrahydroxychalcone.4-HydroxylonchocarpinChalcone: 3,4,2′,4′-Tetrahydroxy-5,3′-digeranylchalcone [67, 468]  D. poinsettiifolia Engl. Not signalized Twigs Botswana Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. Grenylated and prenylated flavonoids. In addition, the flavone 5,7,4-trihydroxy-8-prenylflavone (licoflavone C), the chalcones 4,2′,4′-trihydroxy-3′-prenylchalcone (isobavachalcone) and isobavachromene, the triterpene butyrospermol, and the carotenoid lutein. [67, 206, 289]  D. zenkeri Engl. Not signalized Twigs Botswana Used for snakebite and to treat infection, rheumatism, headache, cough and stomach pain. 3′,4′-(3-hydroxy-2,2-dimethyldihydropyrano)-4,2′-dihydroxychalcone and a bichalcone.4-Hydroxylonchocarpin.p-hydroxybenzaldehyde, dorsmanin A, 4,2′,4′-trihydroxychalcone and 4,2′,4′-trihydroxy-3′-prenylchalconeChalcones: 4,2′,5′′-Trihydroxy-6′′,6′′-dimethyldihydropyranol[2′′,3′′:4′,3′]chalcone [67, 468]  Moringaceae  Moringa oleifera Lam. Horse-radish treeDrumstickMoringoZakalanda Root West AfricaZimbabwe Anti-inflammatory activity.Used as aphrodisiac and to treat asthma, gout and rheumatism. Not identified [469]  Myrtaceae  Eucalyptus camaldulensis Dehnh. Not signalized Leaves Egypt Antioxidant activity Not identified [470]  Polygonaceae  Polygonum senegalense  Meisn. Fotsimbarin’akoholahy Leaves Madagascar  Flavonoids: quercetin, kaempferol and luteolin and their glycosides such as dihydrochalcone glucoside and quercetin glycosides. [413, 471]  Rumex abyssinicus Jacq. Mekmeko Leaves N. Africa - Ethiopia Anti-inflammatory propertiesUsed to treat itching, skin eczema and leprosy. Flavonoids. [337, 472]  R. nervosusVahl., AlcgangoDengogo Leaves Ethiopia Anti-inflammatory properties.Used to treat acne, wounds, eczema, typhus and as an ophthalmic antiseptic. Not identified [337]  Rubiaceae  Nauclea latifolia Smith Pin Cushion TreeÌgíyàà Leaves and root Nigeria Used as anthelmintic and to treat malaria, fever, stomachache and liver diseases. Proanthocyanidins. [12, 58, 473–475]  Solanaceae  Datura stramonium L. Thorn-apple rwiziringa Seeds South Africa Antioxidant activity.Used to treat asthma, headaches and wounds. Not identified [188]  Tiliaceae  Grewia occidentalis L. Cross-berryFour-corner Bark South Africa Antioxidant activity.Used to treat bladder ailments, wounds, impotence and sterility, and to help in childbirth. Not identified [188]  Vahliaceae  Vahlia capensis (L.f) Thunb. Vahlia of the Cape Zimbabwe  Used to treat bacterial infections. Kaempferol, quercetin, afzelin, astragalin, quercitrin, isoquercitrin, rutin, gallic acid, chiro-inositol, dulcitol, and a novel biflavonoid, VC-15B (vahlia biflavone) [475]  Vitaceae  Cyphostemma natalitium (Szyszl.) J.v. d. Merwe Tick-berry bush Root South Africa Anti-inflammatory and anti-microbial agents with significant inhibition of COX-1 Not identified [374]  Rhoicissus digitata Gilg. & Brandt Wilde patatat Roots, stems and leaves South Africa At high concentrations possessed some prooxidative properties. Anti-inflammatory and anti-microbial agents with significant inhibition of COX-1.Used to facilitate delivery. Not identified [364, 374]  R. rhomboidea  (E. Meyer ex Harvey) Planchon Glossy forest grape Roots, stems and leaves South AfricaMozambique Radical scavenging activity, inhibitory effect on xanthine oxidase activity, prevention of lipid peroxidation and damage to DNA and ability to chelate iron. Anti-inflammatory through inhibition of COX-1. Not identified [364, 374]  R. tomentosa (Lam.)Wild & R.B.Drum. Wild grape Forest Grape, Monkey rope, Roots, stems and leaves South Africa Antioxidant and anti-inflammatory activities.Anti-inflammatory through inhibition of COX-1.Used to facilitate delivery. Not identified [364, 374]  R. tridentata (L.f.) Wild & Drum. Bitter grapeBushman’s grapeIsinwazi Roots, stems and leaves South Africa: Venda Radical scavenging activity, inhibitory effect on xanthine oxidase activity, prevention of lipid peroxidation and damage to DNA and ability to chelate iron. Anti-inflammatory through inhibition of COX-1.Used to treat colds, infertility and stomach ailments. Not identified [364, 374, 476]Many edible and culinary herbs and condiments were also included in these two tables as they were used in certain instances as medicinal herbs to treat diseases. These included fruits and seeds ofBalanites aegyptiaca, leaves ofBoscia senegalensis, leaves ofEntada africana and seeds ofParkia biglobosa, from Niger [11], also leaves, seeds, and stem-bark ofMangifera indica from Benin and Burkina Faso [12, 13], leaves ofCynara scolymus from Ethiopia [14, 15], leaves ofAspalathus linearis from South Africa [16–21], leaves ofCinnamomum zeylanicum from Madagascar and Ethiopia [22–24], essential oils from the bark and leaves ofRavensara aromatica from Madagascar [23, 25], buds ofSyzygium aromaticum from Madagascar [23], seeds ofTrigonella foenumgraecum from Ethiopia and Morocco [26–28], and oils in seeds ofNigella sativa from African countries of the Mediterranean region [29–31].


## 2. Tests Used to Assess Antioxidant Activities of African Medicinal Plant Extracts

A variety of test systems were employed to assess the antioxidant properties of the medicinal plant extracts and compounds listed in Tables1 and 2. A comprehensive list of the methods used in antioxidant activity determination, as well as their merits and demerits, has already been published [343–346]. The methods used in the determination of antioxidant activity of natural products and isolated compounds result in varied outcomes when the same samples are tested in different laboratories and by other researchers [347]. Furthermore, results of different methods cannot be correlated, as contradictory results are usually obtained. Hence, although several assays are available, none of them is capable of accurately and completely determining the antioxidant activity of a test substance because of the complex nature of the redox-antioxidant systemin vivo (Figure 2). Based on this complexity, antioxidants are broadly classified as (i) inhibitors of free radical formation, (ii) free radical scavengers, (iii) cellular and tissue damage repairers, and (iv) signalling messengers [347].Figure 2
Mechanism of antioxidant action in wounds.The inhibition of free radical formation could protect against oxidative damage by suppressing the formation of active ROS/RNS. This typically involves reduction or inhibition of substrates required for free radical formation such as metal ions like iron (Fe) and copper (Cu). The sequestration of these metal ions by antioxidant compounds like ellagic acid and glutathione is known to suppress formation of hydrogen peroxide (H2O2) and other free radicals [348, 349]. Furthermore, increasing evidence suggests a relationship between metal overload and several chronic diseases through the induction of oxidative stress [350]. Therefore, inhibition of free radical formation using metal ions as targets could be useful therapeutically. Antioxidant assays designed for this purpose include the cupric and ferric reducing antioxidant power (CUPRAC/FRAP). These methods measure the ability of antioxidants to reduce cupric (Cu2+) and ferric (Fe3+) ions, respectively.Another mechanism by which antioxidants act is through the suppression of oxidative stress by directly scavenging active free radicals. Most commonly reported antioxidant assays such as 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2′-diphenyl-p-picrylhydrazyl radical (DPPH), oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), total oxyradical scavenging capacity (TOSC), and total radical antioxidant parameter (TRAP) are focused on testing the ability to scavenge free radicals. Furthermore, there are diverse cellular antioxidant assays that assess the ability of antioxidant compounds and substances to protect cells against excessive free radical generation. Such assays involve the use of a fluorescent compound such as 2,7-dichlorofluoroscein to determine the ability of test samples to quench intracellularly generated free radicals and inhibit radical formation and lipid peroxidation [345].There are also numerous reports of the ability of antioxidants to repair damaged tissues and improve healing. Topical application of kojic acid and deferiprone, two compounds with the ability to scavenge free radicals, enhanced healing of wounds in rats [351]. Also, the mitochondria-targeted antioxidant, 10-(6′-plastoquinonyl) decyltriphenylphosphonium, accelerated wound closure, stimulated epithelialization, granulation tissue formation, and vascularization, and lowered lipid peroxidation in mice [352]. Moreover, an antioxidant peptide (cathelicidin-OA1) promoted wound healing in a mouse model with full-thickness skin wounds, accelerated reepithelialization and granulation tissue formation by enhancing the recruitment of macrophages to the wound site, and induced cell proliferation and migration [353]. Some antioxidants have also been reported to contribute to healing by enhancing the activity of endogenous antioxidant compounds and enzymes. The induction of the nuclear factor E2-related factor 2-(Nrf2) mediated antioxidative pathway by a rhomboid family protein (RHBDF2) promoted healing of injured tissues, suggesting a relationship between antioxidant gene induction and healing [354]. Niconyl-peptide enhanced wound healing and protected against hydrogen peroxide-induced cell death by increasing the expression of Nrf2 expression in human keratinocytes [355].The most common tests used to determine the antioxidant activity of samples included the assessment of the ability to scavenge free radicals such as DPPH, ABTS+ [16, 19, 35, 62, 85, 94, 98, 99, 139, 158, 175, 184, 187, 266, 282, 302, 356–364], or the hydroxyl radicals [79, 188, 267, 365, 366], as well as the hydroperoxyl radicals by the Briggs-Rauscher reaction [104]. The ability of the extracts to chelate metal ions was also determined as further indication of their ability to contribute in the reduction of free radicals such as the hydroxyl radical [114]. In addition, assessment of the ability of these medicinal plant extracts to protect against lipid peroxidation was also included, which in turn was measured by the malondialdehyde-thiobarbituric acid (MDA) test [320, 367], the modified thiobarbituric acid reactive species (TBARS) assay [18, 22], or conjugated diene formation [367]. Moreover, lipid peroxidation was assessed using the fluorescent probe, diphenyl-1-pyrenylphosphine (DPPP) [188], or using the inhibition of Cu(2+)-mediated oxidation of human low-density lipoprotein (LDL) [187, 367]. The ability of extracts to protect against damage to DNA using the Comet assay was also employed [114, 188].The antioxidant capacity of the medicinal plant extracts was determined using either the TEAC or FRAP assays [11, 85, 302, 313, 321, 368]. The ability of extracts to modulate the gene expression of the antioxidant enzymes, such as Cu, Zn-superoxide dismutase (Cu, Zn-SOD), Mn-superoxide dismutase (Mn-SOD), catalase, and glutathione peroxidase (GPx), was also used as a measure of their antioxidant properties [293]. The photochemilumiescence (PLC) assay is a more recent antioxidant capacity assessment method and was employed for the evaluation of antioxidant capacity of baobab fruit pulp extracts [369].Anti-inflammatory properties of these extracts were assessed by their ability to inhibit 5-lipoxygenases [94, 370, 371] or cyclooxygenase (COX-1 and COX-2) activities [65, 275, 317, 372, 373]. Using the former [374] and the latter [264, 331] methodologies, respectively, a great number of South African medicinal plant extracts were screened for their anti-inflammatory properties. The effect of medicinal extracts on the biosynthesis of different prostaglandins was assessed as a measure of their anti-inflammatory effect [239, 337, 375]. Extracts ofPodocarpus species were shown to inhibit the activities of the COX enzymes [317]. Once again, using this test, the anti-inflammatory properties of the aqueous and ethanolic extracts of 39 plants used in traditional Zulu medicine were screened [376]. The Hen’s Egg Test-Chorioallantoic Membrane (HET-CAM) assay which utilizes the CAM’s capillary system in bred hen eggs was also used to assess the anti-inflammatory activity through antiangiogenic effects of the ethanol and aqueous extracts ofDrosera rotundifolia andD. madagascariensis [155].The antioxidant and anti-inflammatory abilities of the herbal extracts were further assessed by evaluating their ability to control the production of ROS produced by oxidative burst in neutrophils stimulated with L-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) [21, 246]. The inhibition of neutrophils elastase was used as a measure of anti-inflammatory property and it was proposed that the presence of flavonoids such as hyperoside, quercetin, and isoquercitrin inD. rotundifolia [377] and five flavonoid compounds in twoPolypodium species (P. decumanum andP. triseriale) [378] were thought to contribute to this anti-inflammatory activity. These and otherin vitro tests were used to assess the antioxidant properties of three Ghanaian species:Spathodea campanulata,Commelina diffusa, andSecamone afzelii [63].Inflammation is a complex mechanism with many pathways. Several extracts derived from medicinal plants have been shown to modulate or inhibit the activities of mediators of inflammation. For instance, kolaviron, a bioflavonoid compound isolated from the seeds ofGarcinia kola, has been reported to possess anti-inflammatory and antioxidant activities via its effects on COX-2 and inducible nitric oxide synthase (iNOS) by inhibiting the expression of nuclear factor kappa B (NF-κB) [115]. Quercetin is a flavonoid molecule ubiquitous in nature and functions as an antioxidant and anti-inflammatory agent. Dose- and time-dependent effects of quercetin have been investigated on proinflammatory cytokine expression and iNOS, focusing on its effects on NF-κB signal transduction pathways in lipopolysaccharide-stimulated RAW 264.7 cells by using real time polymerase chain reaction (RT-PCR) and immunoblotting. Curcumin, a yellow pigment of turmeric, has been shown to exhibit anti-inflammatory activity. Curcumin has been found effective in the treatment or control of chronic inflammatory conditions such as rheumatism, atherosclerosis, type II diabetes, and cancer [203]. Calixto et al. reported that the anti-inflammatory action of active spice-derived components results from the disruption of the production of various inflammatory proteins (e.g., cytokines such as tumour necrosis factor-alpha (TNF-α), iNOS, and COX-2) [379].Animal studies were also conducted to assess the antioxidant properties of several medicinal extracts. The antioxidant potential ofHypericum perforatum, containing many polyphenolic compounds, was evaluated on splanchnic artery occlusion (SAO) shock-mediated injury [477] and also against elevated brain oxidative status induced by amnestic dose of scopolamine in rats [126]. Some medicinal plant extracts were tested for their ability to protect against carbon tetrachloride-, 2-acetylaminofluorene- (2-AAF-), and galactosamine-induced liver as well as aflatoxin B1-(AFB1-)induced genotoxicity. Using this test, it was found that an extract ofGarcinia kola seeds [116, 478, 479], a decoction ofTrichilia roka root [270], extracts ofEntada africana [442], andThonningia sanguinea [98, 480] possessed protective abilities. The antioxidant properties of plant extracts against potassium bromate (KBrO(3))-induced kidney damage showed the ability ofG. kola seed extract to protect the kidneys [481].Animal studies were also used to assess the anti-inflammatory ability of a great number of medicinal plant extracts using the carrageenan-induced rat paw oedema model. Plants investigated include seed extracts ofPicralima nitida [399], crude methanol extract of the root ofMoringa oleifera [469], powdered leaves and root ofMallotus oppositifolium [167], methanolic extract ofPicralima nitida fruit [400], hot water extract ofAlstonia boonei root-bark,Rauvolfia vomitoria root-bark, andElaeis guineensis nuts [56], secondary root aqueous extract ofHarpagophytum procumbens [303], crude extracts ofSphenocentrum jollyanum [272], aqueous and methanolic extracts ofHypoxis hemerocallidea corm [482], aqueous and methanolic extracts ofSclerocarya birrea stem-bark [483], aqueous extract ofMangifera indica stem-bark [13], aqueous extracts ofLeonotis leonurus leaves [484], leaf extracts ofBryophyllum pinnatum [148], methanol extracts of the stem-bark ofAlstonia boonei [485], aerial parts ofAmaranthus caudatus[486], methanolic extracts ofKigelia pinnata flower [415], and leaf and twig extracts ofDorstenia barteri [276]. In all of these studies, the anti-inflammatory effect against carrageenan-induced rat paw oedema was attributed to flavonoids and other polyphenolic compounds. Animal tests also employed to assess the anti-inflammatory effects of the medicinal plant extracts included inflammatory cell response such as neutrophil chemotaxis and degranulation [112, 487], antiatherosclerosis effects [486], and pain assessment in experimental animals [117].The effect of the medicinal plants on the induction or inhibition of drug metabolizing enzymes was also studied in animals. The effect of the aqueous extract ofThonningia sanguinea on 7-ethoxyresorufin O-deethylase (EROD, CYP1A1), 7-pentoxyresorufin O-dealkylase (PROD, CYP2B1/2), 7-methoxyresorufin O-demethylase (MROD, CYP1A2), aniline hydroxylase (aniline, CYP2E1),p-nitrophenol hydroxylase (PNPH, CYP2E1), and erythromycin N-demethylase (ERDM, CYP3A1) in rat liver was found to selectively modulate CYP isoenzymes [100] and suppress CYP3A2 and CYP1A2 gene expression [101].


## 3. Compounds Isolated from African Medicinal Plant Extracts with Confirmed Antioxidant Activities

Several medicinal plant extracts were studied at research centres in African countries for their antioxidant properties. The major findings of these investigations have indicated that, in addition to known antioxidant compounds such as ascorbic acid in the seeds ofParkia biglobosa [204] and fruits pulp ofAdansonia digitata [369], alpha-tocopherol in methanol extracts of the stems ofSecamone afzelii [62] or from the seeds [38] and methanol extracts of leaves ofAmaranthus caudatus [39], and apigenin and luteolin in aerial parts ofBulbine capitata [66], several other antioxidant compounds were identified. Although known antioxidant compounds such as ascorbic acid have been confirmed to promote wound healing, not all the newly identified compounds have been tested for such activity [488–491].The identified compounds included mainly flavonoids such as flavones and flavonols, flavone and flavonol glycosides, chalcones and dihydrochalcones, and flavonones, although some anthocyanins, proanthocyanidins, and anthrones were also isolated with antioxidant properties. A wide range of plant extracts investigated have been shown to contain flavonoids.Dorstenia species are rich in flavonoids some of which are unique to this genus [67, 205], namely, prenylated flavonoids as found inDorstenia kameruniana and twigs ofD. mannii [206, 207]. Earlier studies have shown that prenylated flavonoids had antioxidant properties, which protected human LDL from oxidation [208]. Those isolated from African medicinal plant extracts were also tested and their antioxidant properties confirmed. The antioxidant activities of three prenylated flavonoids fromD. mannii (6,8-diprenyleriodictyol, dorsmanin C, 7,8-(2,2-dimethylchromeno)-6-geranyl-3,5,3′,4′-tetrahydroxyflavonol and dorsmanin F, (+)-7,8-[2′′-(1-hydroxy-1-methylethyl)-dihydrofurano]-6-prenyl-5,3′,4′-trihydroxyflavanone) against LDL oxidation and also their free radical scavenging activity have been indicated [187]. Similarly, a diprenylated chalcone, Bartericin A, present inD. barteri leaf and twig extracts was shown to have potent antioxidant properties. It was found that this and other prenylated and geranylated chalcones were as active as the prenylated flavones and may account for the anti-inflammatory action of these extracts [276]. Free radical scavenging activity was also confirmed for prenylated anthronoids isolated from the stem-bark ofHarungana madagascariensis[121] and for proanthocyanidins isolated from the bark ofBurkea africana [175]. The anti-inflammatory and antioxidant activities of kolaviron, a biflavonoid isolated from aGarcinia kola seed extract to scavenge free radicals, which protect against lipid peroxidation and H2O2-induced DNA strand breaks and oxidized bases, were also reported [114, 116–119, 209]. In addition, the ability of free radical scavenging activity and ability to inhibit lipid peroxidation of Thonningianin A and Thonningianin B, ellagitannins, isolated fromThonningia sanguineahave been shown [99, 366]. The anti-inflammatory ability of Griffonianone D ((7E)-(6′′,7′′-dihydroxy-3′′,7′′-dimethyloct-2′′-enyl)oxy-4′-methoxyisoflavone), an isoflavone present inMillettia griffoniana, has been established [195]. Prenylated anthronoids, harunmadagascarins A (8,9-dihydroxy-4,4-bis-(3,3-dimethylallyl)-6-methyl-2,3-(2,2-dimethylpyrano)anthrone and B (8,9-dihydroxy-4,4,5-tris-(3,3-dimethylallyl)-6-methyl-2,3-(2,2-dimethylpyrano)anthrone), harunganol B, and harungin anthrone from the stem-bark ofHarungana madagascariensis have exhibited significant antioxidant activity [121]. Saponins and isofuranonaphthoquinones isolated from different medicinal plant extracts showed antioxidant properties and include the saponin, Balanin 1 (3β,12β,14β,16β) cholest-5-ene-3,16-diyl bis (β-d-glucopyranoside)-12-sulphate, sterol sulfonated, Balanin 2 (3β,20S,22R,25R)-26-hydroxy-22-acetoxyfurost-5-en-3-yl-rhamnopyranosyl-(1→2)-glucopyranoside, and a furostanol saponin isolated fromBalanites aegyptiaca [104]. Isofuranonaphthoquinones isolated from the roots ofBulbine capitata, 5,8-dihydroxy-1-tigloylmethylnaphtho[2,3-c]furan-4,9-dione, 1-acetoxymethyl-8-hydroxynaphtho [2,3-c]furan-4,9-dione, and 1-acetoxymethyl-5,8-dihydroxynaphtho[2,3-c]furan-4,9-dione possess antioxidant activities [68]. Though none of these antioxidant compounds has been directly assessed for wound healing potential, the enhanced wound closure observed with treatment of prenylated flavonoids such as genistein [492] and the demonstrated effect of chalcones on the inflammation process [493] attest to the potential of isolated antioxidants in wound management.


## 4. Crude Extracts of African Medicinal Plants with Confirmed Antioxidant Activities

The antioxidant properties of a larger proportion of African medicinal plants listed in Tables1 and 2 were tested using either aqueous or organic plant extracts. After confirming antioxidant properties, a correlation was proposed between this property and the general groups of antioxidant compounds that are present in these extracts. No further attempts were made to isolate the specific compounds that may have contributed towards this property. Flavonoids inAloe barbadensis [32], chromone glycosides inA. claviflora [35], essential oils inArtemisia abyssinica, andJuniperus procera [79] as well asHelichrysum dasyanthum,H. felinum,H. excisum, andH. petiolare [94], proanthocyanidins inBurkea africana bark [175], polyphenols in extracts ofCrataegus monogyna [321], saponins, and alkaloids in extracts ofLeucosidea sericea[210, 211] are all considered as major compounds that have contributed to the antioxidant properties of these plants. Reports on a number ofBarleria species, which includesB. albostellata, B. greenii, andB. prionitis, have indicated their anti-inflammatory [212] and antioxidant capacities [213]. Unlike the isolated compounds, most of the plants listed for possessing antioxidant activity, including extracts ofAgerantum conyzoides,Euphorbia hirta, Kigelia africana, and Nauclea latifolia,have been shown to possess wound healing ability [494–496].Furthermore, studies have focused on screening a vast number of plants, used in a specific region, so as to determine their antioxidant properties, Mali [357], South Africa [19, 188, 267, 364], Cameroon [182, 313], Algeria [85], Ghana [98], Burkina Faso [266], Madagascar [23], and Mauritius [293], and anti-inflammatory properties, South Africa [168, 264, 374, 376] and West Africa [400].


## 5. Discussion and Conclusion

The use of traditional herbal remedies as alternative medicine plays a significant role in Africa since it features extensively in primary health care. The search for natural antioxidants, especially from plant sources, as a potential intervention for treatment of free radical mediated diseases is an important research field, especially for those in developing countries. Many polyphenols, including phenolic acids, flavonoids (anthocyanins and anthoxanthins), tannins, and lignans, are known to act as antioxidants and protect against various pathological conditions such as coronary artery disease and wounds, in addition to their anti-inflammatory, antimicrobial, and anticancer activities [214–216].Flavonoids are a large group of compounds containing several hydroxyl groups on their ring structures and include isoflavonoids and isoflavonoid glycosides, flavones, and flavone glycosides, flavonols and flavonol glycosides, anthocyanins, chalcones and dihydrochalcones, aurones, flavonones and dihydroflavonols, and flavans and biflavonyls. To date, approximately 9000 different flavonoids have been identified from plant sources [217]. Great interest has been dedicated to the antioxidant properties of flavonoids that may function as potent free radical scavengers, reducing agents, and protectors against peroxidation of lipids [208, 218]. Reviews have been published documenting numerous studies on antioxidant efficacy of flavonoids and phenolic compounds as well as on the relationship between their antioxidant activities, as hydrogen donating free radical scavengers, in relation to their chemical structures. The importance of the unsaturation in the C ring of quercetin compared to catechin in the increased antioxidant activity of the former has been presented [216, 219–223]. Also, the importance of the position and number of hydroxyl groups on the phenolic rings in increasing or decreasing the antioxidant properties of these compounds has been emphasized [216, 219–223].Although many flavonoids have been isolated from different African medicinal plant extracts, the structure-activity relationship of these compounds has not yet been investigated. Recent studies have also shown that some flavonoids are modulators of proinflammatory gene expression, thus leading to the attenuation of the inflammatory response [224]. Examples of these include the lipophilic flavones and flavonols 5,7-dihydroxy-2′,3′,4′,5′-tetramethoxyflavone, 5,4′-dihydroxy-7,2′,3′,5′-tetramethoxyflavone, and 5,7,4′-trihydroxy-2′,3′,5′-trimethoxyflavone isolated fromPsiadia punctulata [225] and Dinklagin B and C isolated fromDorstenia dinklagei [226]. Isolated flavone and flavonol glycosides include kaempferide 3-O-beta-xylosyl (1→2)-beta-glucoside, kaempferol 3-O-alpha-rhamnoside-7,4′-di-O-beta-galactoside, kaempferol 3,7,4′-tri-O-beta-glucoside and quercetin 3-O-[alpha-rhamnosyl (1→6)] [beta-glucosyl (1→2)]-beta-glucoside-7-O-alpha-rhamnoside fromWarburgia ugandensis, and quercetin-7,4′-disulphate fromAlchornea laxiflora[159]. Flavanones and dihydroflavonols include dorsmanin I and J and epidorsmanin F and G isolated fromDorstenia mannii [227] and Dinklagins A, isolated from the twigs ofDorstenia dinklagei [226] and two flavones isolated from the twigs ofEriosema robustum [182] and 1α,3β-dihydroxy-12-oleanen-29-oic (1), 1-hydroxy-12-olean-30-oic acid (2), 3,30-dihydroxyl-12-oleanen-22-one (3), and 1,3,24-trihydroxyl-12-olean-29-oic acid (4), a new pentacyclic triterpenoid (1α, 23-dihydroxy-12-oleanen-29-oic acid-3β-O-2,4-di-acetyl-l-rhamnopyranoside) (5) fromCombretum imberbe[138]. Anthocyanins isolated include the cyanidins 3-O-(2′′-galloyl-β-galactopyranoside) and 3-O-(2′′-galloyl-6′′-O-α-rhamnopyranosyl-β-galactopyranoside) fromAcalypha hispida [228] and cyanidin 3-O-β-D-glucopyranoside and cyanidin 3-O-(2-O-β-D-xylopyranosyl)-β-D-glucopyranoside fromHibiscus sabdariffa [266]. When revising the literature, it became apparent that even though most of these medicinal plants and compounds have confirmed antioxidant activity, not many of them have been screened for wound healing potential. As there is an association between antioxidative therapy and wound healing, research in this direction is as imminent as it is important. Furthermore, structure-activity studies on the isolated compounds from African medicinal extracts will be of great interest.Antioxidants may exert their protective effects via different mechanisms at different stages of the oxidation process. There are those that are able to inhibit the production of free radicals via their ability to chelate transition metal ions and those that are able to quench and stabilise free radicals [229, 230]. Additionally, they are further subdivided into categories according to their functions [230]. Such classification of the newly isolated antioxidant compounds from African medicinal plant extracts is warranted to better understand their antioxidant properties.It should be noted that the antioxidant activity of the extracts and compounds listed in this review was mostly determined using either single assays orin vitro analysis. It is therefore possible that some of these extracts and compounds may not show antioxidant activity when alternative testing methods are used. Furthermore, althoughin vivo studies are encouraged, most studies cited usedin vitro assays. As antioxidant activityin vitro does not necessarily translate to activityin vivo, due to pharmacokinetic and pharmacodynamic processes that occursin vivo, it is possible that samples may not be active when tested in animals. Activity of such samples should therefore be confirmed using animal models.Additionally, attempts should be made to identify the compounds responsible for the proven antioxidant properties where not yet done, and in cases where they have been isolated, their wound healing properties should be investigated. If the activity of the compounds and plants identified in this review is confirmedin vivo, they could serve as viable sources for the treatment of wounds in future.



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*Source: 4089541-2018-11-22.xml*