International Journal of Biological Macromolecules 92 (2016) 942–956

Contents lists available at ScienceDirect

International Journal of Biological Macromolecules
journal homepage: www.elsevier.com/locate/ijbiomac

Konjac glucomannan, a promising polysaccharide of Amorphophallus
konjac K. Koch in health care
Sudhanshu S. Behera a,∗ , Ramesh C. Ray bab

Department of Fisheries and Animal Resource Development, Government of Odisha, India
ICAR-Central Tuber Crops Research Institute (Regional Centre), Bhubaneswar 751 019, Indiaa r t i c l e

i n f oArticle history:
Received 5 May 2016
Received in revised form 25 July 2016
Accepted 28 July 2016
Available online 30 July 2016
Keywords:
Konjac glucomannan (KGM)
Polysaccharide
Health beneﬁts

a b s t r a c t
In recent year, konjac glucomannan (KGM) has attracted more attention due to its non-harmful andnon-toxic properties, good biocompatibility, biodegradability and hydrophilic ability. Moreover, KGM
and their derivatives have several importances in the multidirectional research areas such as nutritional, biotechnological and ﬁne chemical ﬁelds. In the previous article, we have reviewed the nutritional
aspects of KGM covering the various aspects of functional foods, food additives and their derivatives.
This review aims at highlighting the diverse biomedical research conducted on KGM in the past ten
years, covering therapies for anti-obesity, regulation in lipid metabolism, laxative effect, anti-diabetic,
anti-inﬂammatory, prebiotic to wound dressing applications. Moreover, this review deals with global
health aspects of KGM and the disparate health related factors associated with diseases and their control
measures.
© 2016 Elsevier B.V. All rights reserved.

1. Introduction
The konjac glucomannans (KGM) is a water-soluble polysaccharide (dietary ﬁbre) [1,2] isolated from tubers of Amorphophallus
konjac K. Koch, a perennial plant belonging to the family Araceae [3].
It has been cultivated for centuries in Asian countries as a source offood and as an ingredient for traditional Chinese medicine (TCM).
Konjac products are regarded as one of the “top 10 health foods”
by World Health Organization [1,4–6].
The polysaccharide has been largely consumed as a nutritional
supplement [5]. The important health beneﬁts of KGM includes
in reducing cholesterol [7], normalizing triglyceride (TG) concentration in blood [8], improving blood sugar levels [9], promoting
intestinal activity [10] and immune function [11] and wounddressing [12]. KGM is considered as an indigestible dietary ﬁbre

Abbreviations: ACA, American Cancer Association; ADA, American Diabetes
Association; CHD, coronary heart diseases; CMKGM, carboxymethyl konjac glucomannan; eNOS, reduced nitric oxide synthase; FDA, Food and Drug Administration;
GR, glutathione reductase; IBD, inﬂammatory bowel disease; iNOS, inducible nitricoxide synthase; KGM, konjac glucomannan; NCRI, National Cancer Research Institute; OVA, ovalbumin; PKF, puriﬁed konjac ﬂour; SCFAs, short-chain fatty acids;
TCM, traditional chinese medicines; TNF-␣, tumor necrosis factor-alpha; WHO,
World Health Organization.
∗ Corresponding author.
E-mail addresses: ssbehera.nitrkl2013@gmail.com, ssb.behera@gmail.com(S.S. Behera).
http://dx.doi.org/10.1016/j.ijbiomac.2016.07.098
0141-8130/© 2016 Elsevier B.V. All rights reserved.

being resistant to hydrolysis by the action of digestive enzymes
in the human gut [13]. In pharmaceutical industry, KGM is usedin the preparation of hydrogel as a DNA-controlled release matrix[14–17]. In addition, it has been used to improve glycaemia andother related risk factors for coronary heart diseases in Type II
diabetic patients [18,19]. Therefore, KGM is recognized as a safe
biomaterial according to the FDA (Food and Drug Administration,USA) [20,21] for therapeutic uses. Over the last few decades, heteropolysaccharides have gained special importance in the biomedical
and drug delivery systems. Among them, KGM is chosen as a preferred biopolymer [16,22].
In a previous review, we have discussed on the global applications of KGM as food for nutritional beneﬁts [23]. The traditional
utility and potential health beneﬁts of A.konjac K.Koch have beenreported by Chua et al. [4]. In this review, we have discussed thepotential applications of KGM as health food products and different
uses in biomedical sectors in treatment of life style diseases suchas Type 2 diabetes, obesity, coronary heart disease (CHD), stroke,
hyperlipidemia, hypercholesterolemia, diminution of constipation,
treatment of hyperthyroidism, colorectal cancer, wound healing,
and as an antioxidant and prebiotic.

2. KGM and its chemical structure
The chemical structure of polysaccharides has a great impact
on the functional and nutraceutical characteristics and/or on their

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943

Fig. 1. Chemical structure of Glucomannan (KGM)(repeating unit); the M-M-G sequence represents ␤-1, 4 linked of d- glucose (G) and d- mannoses (M) backbone and the
backbone is branches through ␤-1, 6-glucosyl units; the Ac-M-G sequence represents acetyl groups randomly attach at the C-6 position of a d- mannoses (M) unit [Adopted
from 6].

bioactivity [24,25]. However, irrespective of its origin, KGM is a␤-1, 4 linked polysaccharide composed of a d- glucose (G) and dmannoses (M) backbone lightly branched, with branches through␤-1, 6-glucosyl units [6,26–32]. There may be certain short side
branches at the C-3 position of the mannoses and acetyl groups
randomly present at the C-6 position of a sugar unit (Fig. 1). The
acetyl groups frequently range from 1 per 9 sugar units to 1 per
20 sugar units [4,33]. Moreover, the M (d- mannoses): G (d- glucose) ratio may vary depending on the original source of KGM. For
instance, it has been reported that KGM has a M: G molar ratio at
around 1.6:1 in acetylated KGM extracted from of A. konjac [34,35].
Kobayashi et al. [36] investigated the effects of degree of chemical modiﬁcations such as carboxymethylation (introduction ofcarboxymethyl group) in KGM under various conditions and todevelop new applications of KGM. The KGM backbone possesses
5–10% acetyl-substituted residues and the presence of substituted
group beneﬁts KGM for the solubility in aqueous solution. However,the KGM losses its acetyl groups with the treatment of alkalis, and isreadily transformed into a thermally stable gel called KGM gel [37].
The process of gelation is also enhanced by heating. Therefore, theaddition of alkali to KGM not only enhances its solubilisation but
also facilitates the deacetylation of the chain [38].
Recently, Xiao et al. [39] reported that the water binding properties of KGM and carboxymethyl KGM (CMKGM) are important
for their application in food, pharmaceutical, and bio-engineeringﬁelds. The incorporation of carboxymethyl group in the KGM structure has decreased the water adsorption, absorption, and solubilityof CMKGM and hence, decreased the hydrophilicity of the molecule.
The modiﬁcation of KGM structure not only provides fundamental
information for understanding material functions and applications
but also, offers several promising applications such as preparationof biodegradable ﬁlms [40], biomaterial for enzyme encapsulation[41] and in the drug delivery systems [42].
3. Local and traditional uses of KGM
The rounded tuberous root of A. konjac K. Koch was discovered by Chinese and listed as early as 206 BCE in Shen Nong’s
Herbal Classic. It was promptly introduced in Korea, and then in
Japan and included as a commodity and planting programme in the
19th century [43]. At the same time, the FDA (1997) and European
Union (EU) (1998, 2003) recognized and listed konjac ﬂour as GRAS
(Generally Regarded as safe) food additive (nutraceuticals) [44]. It
became an important tuber crop of tropical and sub-tropical countries because of its yield potential and culinary properties. It is now
widely grown and consumed in all south eastern Asian countries
including India, Indonesia, and Malaysia [45].
The tuber of A. konjac K. Koch is used as an important source offood and is grown either as wild or cultivated as a vegetable crop in
Asian and African countries [46]. The KGM extracted from corm of

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A. konjac in the form of ﬂour from which foodstuffs such as noodles
and spaghetti are prepared. Such foodstuffs increase satiety andare used as an anti-obesity agent [47]. Over the past two decades,
KGM has been introduced on a relatively small scale into the UnitedStates and Europe as a food additive [47,48]. Being a low caloric
content and soluble dietary ﬁber-rich food, it can delay stomach
emptying for considerable time [49]. Further, the tuber is a valuable
source for the traditional medicines that are mainly used in China
and Korea for the treatment of liver diseases, abdominal pains, piles,
enlargement of spleen, asthma and rheumatism [46].
4. KGM and health beneﬁts
Since early 1960’s, many scientists worldwide studied thefunctional health properties of dietary ﬁbre and their possible
role in relation to life style diseases such as cardiovascular disease, coronary heart disease, stroke, sudden death, hyperlipidemia,
hypercholesterolemia, diabetes, obesity, and colon cancer [50,51].
While the causes for these life style diseases vary from person
to person, the diet is considered to be one of the important factors. There are increasing evidences that intake of dietary ﬁbre has
functional beneﬁts in lowering these life style diseases. American
Diabetes Association, American Cancer Association, National Cancer Research Institute and other international food and nutrition
organizations have published various scientiﬁc papers to advocate
the advantages of increasing intake of food ﬁbre [52–54].
In China, the A. konjac has been used in TCM as an immuneregulation and healthcare food for a long time [18,55]. In TCM, agel prepared from the puriﬁed konjac ﬂour (PKF) has been used
for more than 2000 years for detoxiﬁcation, tumour-suppression,
blood stasis alleviation and phlegm liquefaction. This gel has been
consumed by the indigenous people of China for the treatment ofasthma, cough, hernia, breast pain, burns as well as in curing of
haematological and skin disorders [56]. Conventionally, the use of
PKF has been related with food applications. On the other hand,
KGM, as a health product, is extensively used in Asian countries andin United States for its novel properties. Being a thickening agent,
it has extraordinary water retention ability, a unique viscosifying
activity and a varying poor (being soluble in alkali) water solubility
that leads to the formation of glucomannan derivatives with different solubility [57]. However, more recently this unique biomaterial
has gained increasing importance in the biomedical and pharmaceutical ﬁelds since KGM controls several functions of organs andorgan systems of human beings (Fig. 2). More speciﬁcally, theseapplications include anti-obesity, regulation in lipid metabolism,
laxative effect, anti-diabetic, anti-inﬂammatory, prebiotic, antioxidant, etc. [45,58]. The global visions of biomedical applications of
KGM are shown in Table 1.
4.1. KGM as alternative therapies for type-2 diabetes
mellitus/reduction of blood glucose
Diabetes mellitus is a chronic metabolic disease that makes
dramatic changes in the lifestyle of patient’s well-being leading
to reduced physical activity with weakening and life-threatening
complications [59,60]. It is one of the common diseases in nearly all
countries with China and India are in the forefront. It has been estimated that the world prevalence of diabetes among adults (aged
20–79 years) was 6.4%, affecting 285 million people in 2010 andwill increase to 7.7%, and 642 million adults by 2030 [7,61]. Moreover, the percentage of prevalence of type 2 diabetes is higher inthe developed than in the developing countries [62,63]. Between
2010 and 2030, there will be 69% increase in numbers of adults
with diabetes in the developing countries and a 20% increase in
the developed countries [64]. The treatment of diabetes and asso-

ciated health-risk aspects are often highly complicated and needconsiderable attentions towards patient’s education and repeated
medical surveillance [7,63,64].
Despite signiﬁcant achievements in various treatment
approaches and preventive measures during the last few decades,
the persistence of diabetes has been rising exponentially and also
represents a major healthcare burden throughout the world [64].
Though, there is a lack of evidences supporting the use of herbal
supplements for the treatment of diabetes, an increasing numberof people are adopting the herbal products such as KGM for remedy[65–69].
Like other soluble ﬁbres (oats, minor millets, guar gum, pectin,
and psyllium), KGMhas been advocated for its beneﬁcial effects on
the risk of coronary heart diseases [18]. Moreover, KGM is scientiﬁcally proven to reduce body weight, decreases the ingestion offoods that increases cholesterol and glucose concentrations, thepost-prandial rise in plasma glucose, hepatic cholesterol synthesis, and increases in fecal elimination of cholesterol containing bile
acids [70,71]. Several clinical trials have investigated the impactof KGM on total cholesterol, LDL cholesterol (LDL- C), HDL cholesterol (HDL- C), TG, plasma lipids, body weight, fasting blood glucose(FBG), and blood pressure (BP) [72,73]. Although KGM is not considered as a drug, some bio-pharmaceutical effects described in theliterature suggest its potential as a bioactive polymer [58]. The KGM
has been found to decrease the serum glucose levels following oral
administration to type-2 diabetic rats [74].
Huang et al. [55] investigated the effect of konjac food on blood
glucose level in patients with diabetes. Seventy-two type 2 diabetic
patients were given konjac food for 65 days. The data accumulated
by multiple F-test suggested that the FBG and the 2-h postprandial
blood glucose (PBG) on the 30th and the 65th days after the food
was ingested were signiﬁcantly reduced. In this context, Vuksan
et al. [18] reported that KGM ﬁbre improved the metabolic control
as measured by glycaemia, lipidemia, and blood pressure in highrisk type 2 diabetic patients. Eleven patients with hyperlipidemic
hypertensive type 2 diabetic males were chosen for participation
with intake of KGM ﬁbre enriched biscuits (approx. 0.7 g/412 kJ[100 kcal]) or wheat bran ﬁbre control biscuits. Compared withplacebo, KGM signiﬁcantly reduced metabolic control primary end
points such as serum fructosamine (5.7%), TC/HDL-C ratio (10%) andsystolic blood pressure (SBP) (6.9%). However, there were no signiﬁcant changes in secondary end points, including body weight,
TC, LDL- C, and HDL-C, TG, applipo-proteins A-1, B, and their ratio,
glucose, insulin, and diastolic blood pressure (DBP) of the treatedsubjects.
Gallaher et al. [75] studied the hypocholesterolemic effect of afood supplement containing equal amounts of chitosan and KGM(1:1 ratio, w/w). Twenty-one overweight normocholesterolemic(normal concentration of cholesterol in blood) patients were fed
with 2.4 g/day of a supplement containing KGM for 28 days. Caloric
intake and intake of fat and dietary ﬁbre (excluding the supplement) did not differ signiﬁcantly between the initial and ﬁnal
period. Serum total, HDL-C and LDL-C were signiﬁcantly lower on
the ﬁnal day as compared to the initial day. There was a trend
towards greater fecal excretion of neutral sterol and bile acids(p = 0.13 and 0.16, respectively) at the end of the trial. Chen et al. [9]evaluated the effects of KGM supplement (3.6 g/day) in hyperlipidemic type-2 diabetic patients for 28 days on blood lipid proﬁleand glucose levels. Twenty-two diabetic subjects (age 64.2 + 8.4
years, BMI (Body Mass Index) 25.5 + 3.2 kg/m2 ) with elevated blood
cholesterol levels (FBG) between 6.7–14.4 mmol/L were selected
for this study. The fasting blood samples drawn from initial and ﬁnal
days of each period were analyzed for plasma lipids and glucose levels, where as faeces collected at the end of experiment period wereanalyzed for neutral sterol and bile acid contents. Compared withplacebo, KGM effectively reduced the plasma cholesterol (11.1%),

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Table 1
Global vision of biomedical and pharmaceutical uses of KGM.
Study design/Duration
Biomedical application
Type II diabetes
21 subjects; multiple F-test analysis; 64 days
11 males; double blind; placebo controlled; crossoverdesign; 2 successive 21 days
21 overweight; non-placebo controlled; 28 days
22 diabetic subjects; randomized; double-blind;placebo controlled; crossover clinical trial; 28 days
18 subjects; double blind, placebo controlled, crossover; 21 days
14 diabetic subjects; random-effects model

KGM dosing and dose forms

Consequence/Result

Reference–
2.4 g/day; KGM capsule
KGM ﬁber enriched biscuits of 100 kcal equivalentAnti-Diabetic
Reduction of FBG and PBG
Signiﬁcantly declined in serum fructosamine,
TC/HDL-C ratio and SBP
Signiﬁcantly reduced Serum TC, HDL-C and LDL-C
Signiﬁcantly reduced TC, LDL-C, TC/HDL-C ratio,
ApoB and FBG
Signiﬁcantly reduced TC, LDL-C, HDL-C

–
[55]
[18]

Signiﬁcantly reduced TC, LDL-C, Triglycerides,
body weight, FBG
Reduced blood glucose levels[19]

2.4 g/day (KGM + chitosan); capsules
3.6 g/day; KGM capsules
10 g/day; granola bars
KGM capsules

[72]
[9]
[76]

Swiss albino mice (male)Corms ﬁne powder; 100 g methanol extracted (1:5,
w/v)

Obesity/cholesterol
110 elderly people; randomized; placebo controlled;
45 days
23 obese children
63 healthy men; double-blind crossover; placebo
controlled design–
Ordinary diet with KGM meal

Anti-obesity
Signiﬁcantly decreased TG, TC, and LDL-C[101]

2–3 caps (DICOMAN) twice a day
Gelatin capsules, each containing 0.43 g KGM

Effective in obese and dyslipidemic children
Effective as a cholesterol lowering agent

[103]
[102]

Laxative effect
50 pregnant females; 1–3 months
20 children; double-blind crossover; placebo
controlled design; neurologically impaired
31 children; double-blind crossover; placebo
controlled design; 4 wk
7 constipated subjects; placebo-controlled;
diet-controlled trial;21 days
80 constipated children; double blind; placebo
controlled; randomized trial; 4 wk–
Sachets with of KGM (1.45 g)
KGM dietary ﬁbre
GM ﬁber (DicoFarm)

Constipation mitigation
Effective and well tolerated
Improved chronic constipation and stool
frequency
Beneﬁcial in treatment of constipation

Diet with KGM supplementation (1.5 g/d)

Improved bowel movement and colonic ecology[99]

KGM (2.52 g/d)

Therapeutic success in constipated children[100]

Inﬂammatory effect
Nc/Nga Mice; 8–9 wk–
Diet with PKGM powder

Balb/c mice; 8 wk

Diet with highly viscous KGM

Anti-inﬂammatory activity
Suppressed scratching behaviour andinﬂammatory immune responses
Prevented allergic rhinitis-like symptoms and IgE
response
Reduced the oxidative and inﬂammatory effects

Groups of 8 rats; 7 wk

KGM 45 g/kg in G and GC composition

Inﬂammatory bowel diseases (IBD)
Healthy volunteers and patients–
KGM hydrolysates

Dietary Fibre (KGM) on Absorption of Vitamin
6 normal and 5 maturity onset diabetics
Prebiotic activity
Balb/c mice (n = 48); 4 wk AIN-93 ﬁbre free diet as
control
Wister mice (n = 40); 14 wk; ‘Standard diet’ as control–
Meal with 3.9 g KGM–
KGM or KGH (both in form of pellets) with 5% (w/w)
cellulose‘Standard diet’ with 5% (w/v) KGH

3 healthy faecal donors male; inulin as control
prebiotic substrate
BALB/c mice; 5 groups (n = 8/group); 10 days
In vitro study

10% (w/v) KGH with 15 mg/ml cellulase and inulin

[186]

[96]
[97]
[98]

[106]
[107]
[108]

–
Improved gut pathogens; topical healing; immune
system–Reduces Vit-E absorption in the intestine–
Modulated cecal and fecal micro ﬂora

–
[112]

Signiﬁcantly reduced faecal Clostridum perfringens
and Escherichia coli counts
Beneﬁcially modulated the faecal microbiota

[120]

[122]
[123]

Capsules (200 mg GMH)

Provided protective and prebiotic effects
Potential prebiotic and inhibited the growth ofpathogenic bacteria (Staphylococcus aureus and S.
typhimurium)
Reduced vaginal infections

KGH at a concentration of 5% (w/v)

Acted as biotherapeutic agent[125]

KGM (dosage of 2.52 g/d); placebo maltodextrin

Effective as therapeutic agent[126]

Wound dressing
In vitro; in vivo (Male Sprague-Dawley rats withwound cut) study
In vivo study (Male Sprague-Dawley rats); 14 days
Treatment of hyperthyroidism
48 patients; randomized; placebo-controlled;
one-blind study designed; 2 groups; 2 months
Colorectal Cancer
Sprague-Dawley rats (n = 8 animals/group); 4 wk–
In vitro drug release; dressed with pure CS and
CS/KGM blend ﬁlm
Dressed with KGM ﬁlm treated with (Ca(OH)2–
Treatment with methimozole (10 mg); propanol(10 mg) with KGM powder–
Fed with KGM (5%, w/w)–
Signiﬁcantly promoted wound healing andhemostatic effect
Epithelial coverage by post-surgery in wounds–
Lowered serum thyroid hormones

–
[129]

–
Reduced colon carcinogenesis–[86]

Antioxidant activity
20 women (BMI: 36.1 ± 4.4 kg/m2) with abdominal
obesity; 4 wk
Male Sprague-Dawley rats (n = 8); 4 wk–
KGM-enriched, Chokeberry (Aronia melanocarpa) juice

Potential antioxidant
Stimulated GPx activity

–
[188]

Fed a high fat (25% corn oil,w/w) ﬁbre-free diet orwith KGM or inulin ﬁber (5%)

Stimulated local and systemic antioxidative
defence system[189]

26 female patients; post antifungal treatment for the
Candida infection; 30 days
26 female volunteers with active lesions of acne
vulgaris
89 children; Double-blind, placebo controlled,
randomized trial

5% (w/w) unhydrolysed- KGM, and KGH
2% (w/v) KGH; peptone water (PW) with 2% (w/v)
KGH; lactone (control)

–
[116]
–
[118]

[121]

[5]

[130]
–
[135]

Abbreviation: BMI: mean body mass index; G: KGM-enriched squid-surimi; GNP-CS/KGM: gentamicin- nanoparticles with chitosan/konjac glucomannan; GPx activity:
glutathione peroxidise activity; GS: KGM–spirulina enriched squid-surimi; LDL-C: low-density lipoprotein cholesterol; MF, modiﬁed fat; NA, not available; KGH, konjac
glucomannan hydrolysate; NCEP, National Cholesterol Education Program Step 2 guidelines; PKGM, pulverized konjac glucomannan; SBP, Systolic Blood Pressure; Standard
diet = “rat and mouse standard diet”; TC: total cholesterol; TG: Triglycerides.

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Fig. 2. Effects of Glucomannan (KGM) on organs and organ systems of human being; KGM act on Liver (controls lipid metabolism); Stomach (regulates Inﬂammatory bowel
diseases-IBD); Kidney (affected from type –II diabetes); Large intestine (Constipation Mitigation), Small intestine (Inﬂammatory bowel diseases-IBD), Rectum (Constipation
Mitigation); Skin (wound dressing); Heart (affected from severe type –II diabetes); Eye (affected from severe type –II diabetes); Thymus and Bone marrow (control immune
system).

LDL-C (20.7%), total/HDL- C ratio (15.6%), ApoB (12.9%) and fasting glucose (23.2%). Fecal neutral strol and bile acid concentrations
were increased by 18.0% and 75.4%, respectively, with KGM supplements. From these studies, it is evident that KGM can be an adjunctfor the treatment of hyperlipidemic diabetic subjects.
Yoshida et al. [76] studied the supplements of plant sterols
and/or KGM on the status of lipid proﬁle and cholesterol biosynthesis in hypercholesterolemic type 2 diabetic and non-diabetic
subjects. Eighteen non-diabetic individuals and sixteen type 2 diabetic individuals were supplemented in their diet with plant sterols,
KGM (10 g/day) and mixture of both (sterol+ KGM). The overall
total cholesterols decreased after feeding with the mixture (sterol+
KGM) (4.72 ± 0.20 mmol/L) as compared to the control (no supplements) (5.47 ± 0.18 mmol/L). Plasma LDL-C concentration was
also lowered (p < 0.05) after KGM (3.16 ± 0.14 mmol/L) and combined treatments (sterol+ KGM) (2.95 ± 0.16 mmol/L) as compared
to control (3.60 ± 0.16 mmol/L). However, there was no signiﬁcantvariation in lipid proﬁle in the subject groups. Chen et al. [77] developed microcapsule composed of sulphate-glucomannan-alginate
barium (SGA) for the treatment of diabetes. This microcapsulation
technique was more effective compared to the traditional microencapsulated APA (alginate-poly-l-lysine-alginate) and Aba (Ba2+ )microencapsulated islets for the treatment of diabetes. The three
types of microencapsulated islets were cultured in vitro and theirmorphology and biochemical activities were studied. SGA microencapsulated islets had higher activity and produced more insulin andcytokine (such as MCP-1. IL-1, IFN-␥, TNF-␣) than the APA and ABa
microencapsulated islets after transplantation. More recently, Shahet al. [78] reported that dietary ﬁbre like KGM improved satiety byproviding bulk and increasing digestion time to slow postprandial
glucose uptake, thereby lowing blood glucose and insulin levels.

Thus, KGM has the ability to improve insulin sensitivity in individuals with type 2 diabetes.
To sum up, KGM is considered as a potentially emerging alternative therapy for treatment of type 2 diabetes. KGM is useful inimproving diabetes control, reducing associated risk factors such as
hyperlipidemia and hypertension, and ameliorating insulin resistance [79,80]. These hypoglycaemic effects were attributed to theinhibition of carbohydrate absorption as well as decrease in the
postprandial insulin ﬂow [55,81–83].
4.2. Anti-Obesity
Obesity is a medical condition in which excess fat has accumulated in the body to the extent that it may have detrimental effect onhuman health, leading to reduced life expectancy and/or increased
health problem [84]. KGM is reported to reduce the absorption
kinetics of obesity fat [85,86]. Li et al. [87] studied the effect ofhigh frequency oscillatory type ball-mill treatment or grain size
effect on structure and anti-obesity potential of konjac ﬂour onobesed rats. The grain size of konjac ﬂour changed from 657.3 ␮m(d50 ) to 23.7 ␮m (d50 ). The structural changes of grain sizes arecharacterized by using X-ray diffraction and differential scanningcalorimeter. With a decrease of the grain size and crystallinity after
4 h of treatment, the milled konjac ﬂour swelled more quickly. The
resultant konjac ﬂour induced signiﬁcantly the antiobesity properties, such as decrease in body weight, glucose, TG, and LDL-C
concentrations in blood of nutritional obese rats. Vasques et al.
[88] extracted a compound, hydroxycitric acid from Garcinia cambogia and mixed it with KGM and studied the pharmacotherapeutic
efﬁciency of double-blind randomized sample for the treatment ofobesity. A signiﬁcant reduction was observed in total cholesterol

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level (−32.0 ± 35.1 mg/dl) and LDL- C levels (−28.7 ± 32.7 mg/dl) in
the treated obese group.
Several groups of researchers evaluated the safety and efﬁcacy of
KGM for achieving weight loss in overweight and obese individuals[9,89,90]. More recently, Zalewski et al. [91] evaluated the effects of
KGM on body weight and BMI in otherwise healthy obese children
and adults. The results concluded that the short term KGM feeding
may help to reduce body weight. The mechanism of action of KGM
is to promote satiety due to delaying in gastric empting caused by“mass effect” of gel-like viscous mass forming in the stomach anddelaying gastrointestinal transmit time.
Zalewski and Szajewska [92] evaluated the efﬁciency of KGM
consumption on body weight in overweight and obese children.
Children (aged 6–17 years) were randomly assigned to receive KGM
or placebo (maltrodextrin) for 3 months and followed-up for 3
months with a dose of 3 g/day. The results did not provide a deﬁnite answer on effectiveness of KGM of overweight and obesity inchildren. However, the study envisaged a research gap in the ﬁeldof konjac research.
In contrast, Onakpoya et al. [93] reviewed the efﬁcacy of KGM in
body weight reduction. Evidence from available randomized clinical trials did not show that KGM intake generated statisticallysigniﬁcant weight loss. In otherwise healthy overweight or obese
adults, there are some evidences to suggest that in the short term
KGM may help to reduce body weight [91].

4.3. Laxative effect/constipation mitigation
Constipation and encopresis are common problems in people
particularly at the old age. It has been reported that dietary ﬁbre
has a pivotal role to play in the management of constipation, andan average intake of about 18–27 g/day of ﬁbre has shown to be
useful in reducing constipation [94,95].
Signorelli et al. [96] investigated the use of a combinationof KGM with lactose in the constipation of pregnanant women.
Fifty pregnant females affected by constipation were treated withsachets containing a preparation of KGM (1.45 g) and glucose(4.2 g), in a posology of 2(1–4) sachets/day for 1–3 months. The
treatment induced a return to normal frequency of weekly numberof evacuations (4.9–5.8/week) and a parallel control of weight gain
(within 20% of initial body weight).The latter ﬁnding seems to berelated to hunger control induced by KGM at the gastric level which
prevents an excessive food intake.
Staiano et al. [97] evaluated the efﬁcacy of KGM as a treatment
for chronic constipation in children with severe brain damage. They
designed a study with 20 children with severe brain damage andchronic constipation by randomly assigning in a double blindedstudy with either KGM or placebo for 12 weeks. Stool habits, total
and segmental gastrointestinal transit times, and anorectal mobility were evaluated in all the children before and after the treatment
period. The experiment revealed that KGM signiﬁcantly increasedstool frequency as compared with placebo. Clinical scores of stool
consistency were signiﬁcantly improved, whereas the occurrencesof painful defecations per week were signiﬁcantly reduced by KGM
but not by placebo. However, neither KGM nor placebo had a measurable effect on total and segmental transit times.
Loening-Baucke et al. [98] evaluated the effect of KGM ﬁbrein the treatment of children with functional constipation withor without encopresis. Forty-six chronically constipated children
were recruited into the study, but only 31 children (aged between
4.5–11.7 years) could complete. KGM ﬁbre (DicoFarm, Rome, Italy)
and placebo were given as 100 mg/kg body weight daily (maximal
5 g/day) with 50 mL ﬂuid/500 mg for four week each. The result conﬁrmed that KGM was beneﬁcial in the treatment of children withfunctional constipation.

947

Chen et al. [95] investigated the gastrointestinal response of
KGM in volunteers and their stools were fully collected to determine the fecal mass, components, microﬂora, and short-chain
fatty acid content. They found that the KGM supplement notably
increased the mean defecation frequency (number/day), dry andweight stool weight (g/d) by ∼27.0%, 21.7%, and 30.2%, respectively.
The increased dry fecal mass was due to the presence of plant- andsoluble materials. However, with the supplement of KGM the bacterial biomass such as lactobacilli, biﬁdobacteria and total bacteria
found elevated in fecal mass (log counts/g wet feces) as examinedby the ﬂuorescence In Situ Hybridization methods. Moreover, KGM
supplement also increased colonic fermentation as conﬁrmed bydecrease in fecal pH and increase in fecal short-chain fatty acids.
Chen et al. [99] further investigated the supplementation of KGM
into low-ﬁbre-fed Chinese diet had promoted bowel movement
and improved colonic ecology in constipated adults. A total of sevenconstipated subjects had participated in the diet controlled linear
study that consisted of a 21 days of placebo period, seven daysof adaptation period, and a 21 days of KGM supplement (1.5 g/d)
period. Stools were collected from individual subject for analysis of colonic indices such as fecal microﬂora, pH, and short-chain
fatty acid content. It was observed that KGM supplement slightly
but signiﬁcantly increased the weekly defecation frequency from
4.1 ± 0.6 to 5.3 ± 0.6 and slightly eased the bowel movement. The
fecal weight (g/d) and percent moisture content were not significantly altered with ﬁbre supplement. Moreover, the KGM intake
increased the fecal concentration (log counts/g wet feces) of lactobacilli, biﬁdobacteria and total bacteria. In addition, fermentationof KGM resulted in greater concentrations of fecal acetate, propionate and butyrate and thus lowers the fecal pH. Chmielewska et al.
[100] investigated the efﬁcacy of KGM as a sole treatment for functional constipation. Children (aged between 3 and 16 years) withfunctional constipation were randomly assigned to receive KGM(2.52 g/day) or placebo for 4 weeks. It was observed that the primary outcome and treatment success (≥3 stools per week with nosoiling) were similar in the KGM and placebo groups (relative risk
0.95). In the KGM group, the stool consistency score was higher
at week 1, lower at week 3 and similar at weeks 2 and 4. Stool
frequency was higher only at week 3 and week 4 but was similar
among groups at weeks 2 and 3. No difference was observed in thefrequency of any other secondary outcome of adverse effects.
Recently, Chiu and Stewart, [10] investigated the digestibility
and fermentability of two different preparations of KGM in vitro,and studied their impact on human health. Konnyaku (yam cakemade from A. Konjac), inulin, and guar, gum were subjected toin vitro digestion and fermentation. The fragmentated samples
were investigated for gas volume, pH, and short chain fatty acid
(SCFA) measurements. Organic acids like acetate, butyrate and propionate were measured with gas chromatography. The results ofin vitro digestion conﬁrmed that KGM and Konnyaku were resistantto degradation by digestive enzymes. In addition, fermentation patterns presented in this study provided a mechanism for the healthbeneﬁts of KGM.
Supplementation of KGM has shown to relive constipation,
which could be associated with increased stool bulk and promotion of the growth of lactic acid bacteria in colon; thus improved
the colonic ecology [10,78,95].
4.4. Regulation of lipid metabolism, reduce blood lipid andcholesterol
The preventive effects of KGM have been observed in a number
studies and found to regulate the metabolic parameters of blood
lipids and cholesterol levels [7].
Zhang et al. [101] investigated the effect of food containing
reﬁned konjac meal on human lipid metabolism. A total of 110

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elderly people with hyperlipidemia were randomly assigned to
one of the two groups. The ‘experimental’ group consumed an
ordinary diet plus foods containing reﬁned konjac meal, and the‘control group’ consumed only the ordinary diet. The experiment
was carried out for 45 days. The results indicated that in the experimental group, blood levels of TG, TC, and LDL-C were signiﬁcantly
decreased at the end of the trial, whereas HDL-C and apoprotein(AI) levels were signiﬁcantly increased. In contrast, for the control group, the changes in the above parameters were insigniﬁcant.
It was observed that the effects of reﬁned konjac meal on lipid
levels in the blood were somewhat different between patientswith hyperlipidemia and those with high risk critical values. For
the former, TG and TC were decreased by 83.8 ± 133.5 mg/dl, and42.4 ± 23.4 mg/dl, respectively; whereas for the latter, these values
decreased by −1.1 ± 23.1 mg/dl and 8.3 ± 18.2 mg/dl, respectively;
the difference mentioned above was statistically signiﬁcant.
Arvill and Bodin [102] investigated the effects of KGM on serum
cholesterol concentrations in 63 healthy men (aged between 25 and65 years) in a double-blinded crossover, placebo controlled design.
The subjects were given identical gelatin capsules, each capsulecontaining 0.43 g KGM (active) or corn starch (placebo) in addition
to 66 mg lactose and 10 mg magnesium stearate. Three capsules
were given three times daily half- one hr before the meals (total
daily amount 3.9 g KGM) with a glass of water. It was observed that
intake of KGM ﬁbre reduced the TC concentrations by 10%, LDL-C
concentrations by 7.2%, TG by 23%, and systolic blood pressure by
2.5%. But, HDL-C and the ratio of LDL-C to HDL-C did not change
signiﬁcantly. In addition, no change in diastolic blood pressure orbody weight was observed.
Livieri et al. [103] investigated the effectiveness of KGM on
childhood obesity. The study has been carried out in 23 obsessed(aged 5.2–15.8 years) children with excess weight of 51 ± 16%,
treated with 2–3 capsules twice a day of KGM ﬁbre (DICOMAN 5:23 gr/die), and in 30 obesed children (aged 5–18 years) with similar
excess weight studied as control. In KGM-treated obsessed children, excess weight and TG levels had decreased drastically morethan in obsessed controls, concomitant with decrease of cholesterollevels, but serum iron, calcium, copper and zinc contents remainunchanged.
More recently, Martino et al. [104] reported, “a low-fat,ﬁber-rich diet” is the ﬁrst step in the management for hypercholesterolemic children. KGM has been demonstrated to lower the total
and LDL-C.
The ability of KGM, especially in regulation of lipid metabolism,
reduces blood lipid and cholesterol and can be a candidate for use
as possible therapeutic tools for the treatment of several diseases
such as diverticulitis, Crohn’s disease or ulcerative colitis [5].

symptoms in mice upon immunization and nasal sensitization with
ovalbumin (OVA). The KGM-fed mice showed a much lower frequency of sneezing than in control animals. In addition, KGM-fed
mice exclusively suppressed OVA-speciﬁc IgE response without
affecting IgG1/IgG2 responses as well as systemic Th1/Th2 cytokine
production. The result suggested that KGM supplementation could
be a beneﬁcial foodstuff in preventing nasal allergy such as seasonalpollenosis.
More recently, Vazquez-Velasco et al. [108] investigatedthe effect of high-fat squid-surimi diets enriched in KGM or
KGM–spirulina on lipemia, liver glutathione status, antioxidant
enzymes, and inﬂammation biomarkers was determined in Zucker
Fa/Fa rats. Groups of eight rats, each received for 7 weeks
the squid-surimi control (C), KGMenriched squid-surimi (KG)
and KGM–spirulina enriched squid-surimi (KGS). The KGS diet
improved superoxide dismutase, catalase, glutathione peroxidaseand glutathione reductase (GR) activities and reduced the endothelial (eNOS) and increased the inducible nitric oxide synthase (iNOS)
and tumor necrosis factor-alpha (TNF-␣) levels. The KGM-enriched
and KGM with spirulina-enriched squid-surimi act as functional
foods by reducing the oxidative and inﬂammatory status in Fa/Fa
rats. Thus KGM enriched surimi diet induced hypocholesterolemic,
antioxidant and proinﬂammatory effects.
4.6. Inﬂammatory bowel disease (IBD)
Inﬂammatory bowel disease (IBD) describes a number of multifactorial disorders which occur in the digestive system. The
conditions of disease development in IBD are affected by the diet,life style and other susceptible endogenous factors including the
gut microﬂora [109]. It has been suggested in recent years thatthe human bowel gut microﬂora produce antigenic factors which
initiate the chronic immune inﬂammation of the bowel mucosa[110]. The chronic immune inﬂammation and subsequent immune
responses cause these intestinal disorders including Crohn’s disease (CD) and ulcerative colitis (UC) [111]. Carbohydrates may
provide an alternative therapeutic approach for a number of digestive health disorders such as IBD.
Suwannaporn et al. [112] investigated the effect of low andhigh weight KGM hydrolysates within healthy volunteers andpatients suffering from IBD and associated gut conditions. The KGM
hydrolysates delivered several biological beneﬁts such as capacity
to bind pathogens and arrest them from binding epithelial cells ofgut, stimulating topical healing, regulating immune systems, andability to generate systemic immune responses. Moreover, the KGM
hydrolysates act as soluble dietary ﬁber and as prebiotic.
4.7. KGM on absorption of vitamin

4.5. Anti-inﬂammatory activity
Anti-inﬂammatory refers to the property of a substance or treatment that reduces inﬂammation or swelling. Inﬂammation is abiological response to noxious stimuli such as pathogens that cause
tissue and cell damage [105].
Onishi et al. [107] examined the effects of dietary pulverized
KGM powder on scratching behaviour and skin inﬂammation inmice (4 week-old NC/Nga), a model of atopic dermatitis. They werefed with diet containing KGM and effects of cutaneous inﬂammation were evaluated (every 2 weeks) by histopathological analysis.
Continuous KGM feeding caused signiﬁcantly decreased eczematous skin lesion including hyperkeratosis, dermal mastocytosis andeosinophilia. Moreover, cutaneous over- productions of substances
P, IL-10, IL-4, and TNF-␣ were restrained in KGM-fed mice. In afurther study, Onishi et al. [108] investigated that feeding with
KGM powder could prevent skin inﬂammation in a murine modelof atopic dermatitis. KGM feeding suppressed allergic rhinitis-like

It has been suggested that high-ﬁbre diets may be beneﬁcial
for diabetics since they reduce the post-prandial blood glucose
and serum lipid levels but the exact mechanisms of their actions
have not yet been clariﬁed [113]. It is considered, however, that
dietary ﬁbres increase the viscosity of the gastrointestinal contents
thereby retard the gastric emptying and delaying absorption by
the intestinal wall [114]. Therefore, their viscosity appears to be amajor factor in suppressing the post-prandial rise in the blood glucose level [115]. The highly viscid ﬁbres such as KGM, guar gum
and pectin appear to have the greatest effect on blood glucose andon lipid metabolism. The serum levels of cholesterol and bile acids
decrease when the mucilaginous ﬁbres are consumed.
Doi et al. [116] investigated the effect of KGM as dietary ﬁbres.
The subjects were given a control test meal, prepared by adding
vitamin B12 (mecobalamin) and vitamin E (tocopherol acetate),
after a 12 h overnight fast. Then, on the second day in the case of thenormal subjects, and on the seventh day in the case of the diabetic

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subjects, the subjects received a second test meal with 3.9 g KGM.
Venous blood samples were taken immediately before the test meal
and again after 1, 3, 5, 8, 12 and 24 h for analysis of vitamins. The
absorption rate of vitamin E into the intestine was reduced when
KGM was added to the test meals, but that of vitamin B12 was
not reduced in normal or diabetic subjects. The results suggested
that KGM reduces fat-soluble vitamin (Vit-E) absorption by removing bile acids, but does not reduce fat insoluble vitamin (Vit- B12)
absorption in the intestine.
4.8. Prebiotic activity
In general, prebiotics can be considered as a ‘food’ forprobiotics. Probiotics can be deﬁned as “live microbial food supplements which beneﬁt the health of consumers by maintaining
or improving their intestinal microbial balance when taken in adequate/prescribed quantity” [117].
Chen et al. [118] conducted the time-course and dosedependent studies to examine and compare effects of unhydrolyzed KGM with those of acid-hydrolyzed KGM (KGMH) on fecal
microﬂora. In addition, short-chain fatty acid concentration in fecal
content was also determined. Seven-week-old mice were fed 5%(w/w) with cellulose and KGM or KGMH diets for 2 or 4 weeks ina time-course study. In a subsequent dose-dependent study, mice
were fed with ALN-93 (American Institute of Nutrition-93) ﬁbrefree diets, supplemented with 2.5%, 5%, or 7.5% of KGM or KGMH
for 4 weeks. The KGM and KGMH signiﬁcantly increased fecal
anaerobes and biﬁdobacteria counts at weeks 2 and 4, respectively,
compared with the cellulose. In contrast, KGM and KGMH significantly decreased fecal Clostridium perfringens counts. In anotherstudy, Al-Ghazzewi et al. [119] investigated the potential use of
KGMH (derived enzymatically from konjac ﬂour) as a prebiotic
for the growth of culture strains of lactobacilli and biﬁdobacteria grown on De Man, Rogosa and Sharpe (MRS) media or in
UHT (Ultra High Temperature) processed milk supplemented withhydrolysates. The KGMH stimulated the growth of lactobacilli.
Moreover, the number of colony forming units (CFU) obtained
from milk containing the konjac hydrolysates were signiﬁcantly(p = 0.01) higher than those containing inulin. Elamir et al. [120]determined the effects of depolymerized mannans and speciﬁcally
KGMH on the colonic microﬂora of mice. In addition, blood glucose and cholesterol were also measured. Twelve-week-old Wistermice were used for a period of 14 weeks and fed with diet containing 5% KGMH. The KGMH promoted the growth of anaerobes
and lactobacilli in treated mice, and signiﬁcant decreased C. perfringens and Escherichia coli counts in fecal matter. Furthermore, there
were increase in average daily feed consumption and weekly bodyweight in the treated group of mice. In addition, the mean ± SD
(mmol/L) of blood glucose and cholesterol was lower in the treatedgroup. Connolly et al. [121] investigated the prebiotic potentialof KGMH by fermentation using batch cultures inoculated withhuman faeces. Bacterial enumeration was carried out using theculture independent technique, Fluorescent In Situ Hybridization(FISH), and short chain fatty acids (SCFA) production was monitored
by gas chromatography. The KGMH selectively encouraged the production of beneﬁcial gut microﬂora (biﬁdobacteria and lactobacilli).
Moreover, the modulation of the microbiota by KGMH and inulin
resulted in a propionic rich SCFA proﬁle, which is hypothesized asa possible mechanism to reduce plasma cholesterol concentrations
in humans.
Yeh et al. [122] determined the effects of diet containing 5%(w/w) unhydrolyzed KGM, and its acid-hydrolyaste fractions, with
degree of polymerization (DP), on the cytotoxicity and DNA damageof fecal water Caco-2 cells. The results indicated that KGM, KGMacid-hydrolysate fractions (KGMH), and oligofructose (as positive
control) diets, showed an increase in the survival rate of fecal949

water-treated Caco-2 cells as compared to ﬁbre- free diet. Moreover, acid-hydrolyaste fraction of KGM (partially hydrolysed KGM)
exerted great positive effects, among KGM-based ﬁbre, on fecal
water-induced DNA damage. In addition, the prebiotic effects ofpartially hydrolyzed KGM were better than that of KGM. It has
been concluded that the fecal probiotics may be the major mechanism for the beneﬁcial effects of KGM and its hydrolysates inprotecting against fecal water-induced DNA damage in Caco-2 cells.
Al-Ghazzewi et al. [123] investigated that the symbiotic combination of lactobacilli with KGMH inhibited the growth of pathogenic
bacteria such as Staphylococcus aureus and S. typhinurium. Growthof S. aureus and S. typhimurium was assessed individually andwhen mixed with Lactobacillus acidophilus in modiﬁed media supplemented with 2% KGMH. The results showed that prebiotic
bacteria out grew the pathogenic bacteria in the presence of KGM
in mixed cultures. Al-Ghazzewi and Tester [124] further investigated that the efﬁcacy of cellulase and KGM hydrolysates (by␤-mannanases) to promote the growth of lactic acid bacteria.
Mannanases (␤-mannanases) hydrolyse ␤-(1–4)-linked mannose
residues randomly in mannans; whereas, cellualses (␤-glucanse)hydrolyse ␤-(1–4)-linked glucose residues. The lactic acid bacteria
growth proﬁles (expressed in colony forming units, as a functionof time) in UHT milk containing KGM hydrolyzed with cellulase
were signiﬁcantly greater than those containing glucose (control)
or konjac glucomannan mannanase hydrolysates.
Tester et al. [5] reported that KGMH could support the healthy
re-colonisation of vaginal microﬂora post infections. A total of 26
female patients (12 controls and 14 treatments; aged between
18–25) were recruited for the study. The patients were randomly
divided into two groups: one group received the antifungal treatment and the other group received a standard antifungal treatment
plus pessary capsules containing 200 mg KGMH (twice a week for
30 days). It was observed that counts of Candida were diminishedcompletely with antifungal treatment in both the groups. Further,
the vaginal health recovery (post antifungal treatment for the Candida infection), especially the presence of healthy microﬂora could
be re-established only with the introduction of KGMH in the vagina
suggesting the beneﬁts of KGMH in a vaginal health format.
Bateni et al. [125] investigated the prebiotic property and effectof KGMH with respect to improving skin health especially the
reduction of infection due to acne vulgaris. Twenty six female volunteers (aged between 18–39 years) with active lesions of acne
vulgaris were included for the study. Patients are assigned randomly into two groups to receive either a standard treatment or aspray formulation containing KGMH at a concentration of 5% (w/v).
Before and during treatment, the skin was evaluated according to
the acne severity index (ASI). The results showed that there was asigniﬁcant improvement of the skin health at the second (20 days)
and third clinical evaluation (40 days) for established (e.g. antibiotics) and KGMH treatments. Overall these data indicated that the
KGMH could be used as a biotherapeutic agent for the treatmentof mild to moderate acne in patients and as an adjuvant treatment
for severe acne vulgaris. However, Horvath et al. [126] assessed theimpact of KGM as the sole treatment for abdominal pain-related
functional gastrointestinal disorders (FGIDs). A total of 89 eligible children, 84 (94%) completed the study and were assigned toreceive KGM, at dosage of 2.52 g/d (1 sachet of 1.26 g 2 times aday), or a comparable placebo (maltodextrin) at the same dosage.
The result suggested that the KGM was more effective than placebo
in receiving therapeutic success in the management of abdominal
pain in children.
From the studies discussed above, it envisaged that the uniqueproperties of KGM hydrolysates make it valuable as a prebiotic thatcan be applied to a wide range of foods, feeds and pharmaceutical products. Therefore, KGM selectively stimulates the productionof beneﬁcial gut microﬂora like probiotics (biﬁdobacteria and lac-

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tobacilli) and proclaims the treatment of abdominal pain-related
functional gastrointestinal disorders.

observed that patients receiving KGM at the of the study had signiﬁcantly reduce serum T3, T4, FT3 and FT4 levels of thyroxin ascompared to patients receiving placebo.

4.9. Wound dressing
4.11. Colorectal cancer
Few studies have evaluated the use of KGM-based materials
in wound dressings applications. However, in recent years, scientists have attempted to apply KGM and KGM based conjugatedbiomaterials such as chtisoan (CS) as wound dressing materials[127]. These are found to be nontoxic, biocompatible, and provide
antimicrobial activities on the wound surface. Moreover, KGM andKGM-based biomaterials can create a moist wound healing environment, absorb excess exudates, allow gaseous exchange, can beremoved easily from the wound surface; thus easily acceptable by
the consumers [127,128].
Fan et al. [129] prepared a novel wound dressings material
from chitosan/KGM (CS/KGM) ﬁlms embedded with gentamicinloaded poly (dex-GMA/AAc) nanoparticles (giving GNP-CS/KGMﬁlms). The conjugated KGM based ﬁlms are considered as promising novel biodegradable and biocompatible wound dressings withhaemostatic capabilities and antibiotic effects for treatment of
external bleeding injuries. To investigate the potential medical application of KGM, Huang et al. [130] treated KGM ﬁlm
with Ca(OH)2 for investigation of its wound dressing potency.
The in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium
bromide assay (MTT-assay) was carried out for the biocompatibility of the Ca(OH)2 -KGM ﬁlm with ﬁbroblast and keratinocyte
cells. However, an in vivo experiment was performed with Male
Sprague-Dawley rats (250–400 g). The results indicated that the
Ca(OH)2 -KGM ﬁlm inhibited the absorption and activation ofplatelets, and effectively promoted wound contractility, particularly at an early healing stage. In addition, histological examination
revealed markedly secretion and development of collagen andgranulation tissue, respectively. The developed tissue further
responsible for epithelial coverage (Days 7 and 14) of post surgery
victim in wounds treated with Ca(OH)2 -KGM ﬁlm. Shahbuddin
et al. [131] synthesized a range of cross-linked KGMs and poly (Nvinyl pyrrolidinone) hydrogels for wound healing applications. The
cross-linked KGM were found to be cytocompatible and stimulated
ﬁbroblast metabolic activity and also enhanced the migration ofboth ﬁbroblasts and ketatinocytes. Al-Ghazzewi et al. [132] investigated the effects of ingested depolymerised KGM on minor woundhealing in mice. The mice were divided into four groups of twenty
each, and healing scores were recorded over eight days. The healingscores claimed stimulation of skin regeneration of wounded skin ofmice.
KGM being a natural polymer possesses better biodegradability,
biocompatibility, and non-toxicity and has remoulded ability thanvarious synthetic materials [133]. It has a three-dimensional polymer network, and when placed in excess water, it readily swells
and holds large volume of water without dissolution [134]. Due tothis exclusive property, KGM acts as a bioactive reagent and is usedin wound dressing application.
4.10. Treatment of hyperthyroidism
A limited study has been conducted with KGM on the reduction of serum thyroxin in hyperthyroidism patients. Azezli et al.
[134] investigated the activity of KGM in the treatment of hyperthyroidism. A randomized, placebo-controlled, one-blinded study
design was used with newly diagnosed 48 hyperthyroid patients(30 patients with Graves’ disease and 12 with multinodulary
goitre). They were assigned to various treatment groups (suchas group I: with methimozole 2 × 10 mg, propranolol 2 × 20 mg,
and KGM 2 × 1.1.3 g and group II:methimazole 2 × 10 mg, propranolol 2 × 20 mg, and placebo powder) daily for two months. It wasColorectal cancer is one among the leading causes of cancer
mortality (approx. 8.5%) worldwide [135,136]. Intake of dietaryﬁbre as supplements provide protection against colorectal cancer by increasing colonic bulk, reducing transit time [137,138],and promoting the production of short-chain fatty acids, whichleads to induce apoptosis, and differentiation of colon cancer cells[139]. Recent studies also suggest that probiotics, such as biﬁdobacteria and lactobacilli, may reduce the colon carcinogenesis[140,141]. The anti-carcinogenic effect of soluble dietary ﬁbres
may be partially mediated by their prebiotic effect [142,143]. Wu
and Chen [86] investigated that KGM potentially reduced the highfat-induced risk in colon carcinogenesis. These soluble ﬁbres also
reduced the fecal lithocholic acid concentration and enhanced thefecal output of biﬁdobacteria and lactobacilli.
4.12. Effect on immune system
Administration of pulverized KGM prevented the developmentof allergic rhinitis-like symptoms and the increase of plasma
immunoglobulin E (IgE) and G (IgG) levels in mice [5,106]. In
this connection, several authors have reported that consuminghydrolysed KGM can help prevent atopic diseases by suppressing
IgE production in mice [144]. Lin et al. [145] reported that KGM
have immuomodulatory effect on immune organ development, andprovide humoral, cellular and mucosal immunity. More recently,
Onitake et al. [11] investigated the role of pulverized KGM in intestinal immunity in a mouse model of oxazolone (OXA)-induced colitis.
In conclusion, on consumption of KGM the serum biochemicalhaematological values such as albumin, total protein, activity ofcreatinine, aspirate aminotransderase and alanine aminotransferase levels signiﬁcantly get affected which enhances the processof biological detoxiﬁcation in animals [146].
4.13. Antioxidant activity
Generally free radicals are produced in large amounts during metabolic disease conditions like atherosclerosis, urolithiasis,
ulcers etc. [147]. They may cause damage to the organs and ultimately lead to fatal effects. Administration of anti-oxidants has aprotective role to play. Several anti-oxidants of plant origin are
experimentally proved and used as effective protective agentsagainst oxidative stress. There are various plants which are used totreat the diseases like ulcer, diabetes, epilepsy and cardio vasculardiseases [46]. One such plant is Amorphophallus spp.
4.14. Drug delivery
In recent years, researchers have focused on natural polymers including polysaccharides, cellulose derivatives, and proteinsas drug carriers/drug delivery systems. These biomaterials havereceived considerable attention for their controlled release of drugs
and targeted speciﬁc delivery sites [148].
Among the natural polymers, KGM is regarded as a potential
carrier for site-speciﬁc bioactive protein drug delivery system.
Xiong et al. [149] designed thermo-sensitive hydrogels drug carriers from KGM copolymerized with N-isopropylacrylamide. The
inﬂuence of several parameters on the swelling properties of hydrogel was determined and in vitro release of model drug bovine
serum albumin was studied at 20 ◦ C and 30 ◦ C in phosphate buffer
solution. The release percentage hydrogel was found nearly 80%

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and 30% after 5 h at 20 ◦ C and 30 ◦ C respectively. Yu et al. [150]developed composite hydrogels from KGM as the macromolecular cross-linking agent for chitosan in drug delivery systems. The
composite hydrogels claimed effective targeted speciﬁc delivery
sites. Korkiatithaweechai et al. [151] studied the controlled releaseof drug, diclofenac sodium from a chitosan-oxidized KGM polymer blended ﬁlm. The controlled release of test drug showed theslowest release rate and gave the highest percentage of encapsulation efﬁciency. Nair and Jyothi [152] prepared cassava starch KGM
based blend ﬁlms suitability for the sustained release of a model
drug, theophylline. The rate of drug release was positively correlated with the degree of degradation of the blend ﬁlms. The study
showed that the blend ﬁlms with appropriate composition (cassava
starch: 1.5 × 10−3 kg and KGM: 1.5 × 10−3 kg) was found relevant
for the sustained release of the drug.
Colon targeting drug delivery systems allowed the local treatment of colonic diseases and constituted an alternative route forsystemic absorption of drugs [153]. Liu et al. [154] prepared a novel
pH-sensitive hydrogel by using KGM and poly (aspartic acid) asa suitable polymeric carrier for site-speciﬁc drug delivery in theintestine. The release proﬁles of test hydrogel from a model drug
5-Flurouracil were studied in simulated gastric and intestinal pH
media. The results indicated that the hydrogel served as a potential device for the delivery of drugs in upper small intestine. In afurther report, Liu et al. [155] prepared a KGM-based capsule forcolon-speciﬁc drug delivery system. The capsule showed a typical pulsatile release proﬁle with a lag time followed by a rapid
release phase. Xu et al. [156] prepared hydrogels from KGM andpoly (methacrylic acid) carrier for colon-speciﬁc drug delivery.
In vitro drug release of hydrogels was investigated under different conditions using model drug 5-ﬂurouracil. The results of in vitro
drug release of hydrogels showed pH sensitive and speciﬁc of enzymatic degradation that are desirable in colon-speciﬁc drug delivery
applications.
The formulated drugs for colon targeting drug delivery system
are a highly effective pharmaceutical approach due to potential for
speciﬁc degradation of excipients by colon enzymes [157]. However, for application KGM as disintegrating and coating material
and their characteristics properties have to be assured considering
the natural abundant of KGM.
4.15. Research on epidemiological study
Recently, several research groups have been carried out systemic review to evaluate the effects of KGM on health and disease
conditions in deﬁned populations. Xiang-Qun Liu and Lv [158] evaluated a systemic review of randomized controlled trials for theeffects KGM on children with constipation. A meta-analysis was
conducted using the random effects model. The result claimed that
KGM moderately increases the defecation frequency of children
with constipation. However, KGM consumption is not associatedwith a reduction in stool consistency. Zalewski et al. [159] studied a systemic review of randomized controlled trials to evaluate
the effects of KGM on body weight and body mass index in healthyobese children and adults. The data suggested that KGM has thepotential to reduce body weight but not body mass index in adults.
However, the data in children were too limited to drawn a deﬁnite
conclusion (Table 2).
5. Other uses of KGM
KGM and its derivatives were also used in many other applications such as in biotechnological and ﬁne chemical ﬁelds. KGM
can be used as encapsulating membrane which entails the holdingof liquid without bursting through a temperature range of about951−20 ◦ C to about 90 ◦ C [160]. They can be used in immobilization ofcells such as recombinant E. coli, yeast, and Biﬁdus bacillus [161].
Moreover, carboxymethyl KGM–chitosan (CKGM–CS) nanocapsules were used for immobilizing enzyme (e.g. l-asparaginase)[161]. The immobilized enzyme has better stability and activity incontrast to the native enzyme [162]. KGM can also be used as ﬁshfeed binder [163,164].
Moreover, the solution and gelling properties of KGM and its
interaction with other hydrocolloids including carrageenan andxanthan have been proved better means for coating and packaging
in food applications [165]. Besides the applications in mentioned
above, KGM and its derivatives were also used in the pharmaceutical area, such as prosthetic implants, bio-adhesive for healing
effects, and recognize mannose receptor in signal transduction
pathway [166–170].
6. Konjac starch and its application
Starch is the major caloric source in a variety of diets of people
worldwide. It is an important ingredient in various tuber crops likecassava (Manihot esculenta Crantz), sweet potato (Ipomea batatas L.)
and Elephant foot yams (Amorphophallus spp.). Two most important
Amorphophallus species of economic importance are A. paeoniifolius[171] and A. konjac [23,172]. The functional properties of A. paeoniifolius starch and ﬂour have been recently studied in production ofcomposite ﬂour [173] and food products developed from A. paeoniifolius tubers have been reviewed [171]. Konjac starch is the second
major nutrient in A. konjac and only lesser than KGM [174,179]. It
has been extracted from A. konjac K. Koch, using 0.1% (w/v) sodium
metabissulphite solution [175]. The Konjac based foods like Konnyaku or Shirataki noodles are traditionally used in Japanese recipe.
In china, the A. konjac is also used in many traditional foods such as
Moyu or Juruo, due to its high starch content, light taste and elastic
in texture [173,176].
A number of physiological effects have been described by several researchers, which have been proved to have health beneﬁts[177,178]. The foods containing konjac starch moderate the rateof digestion, which inﬂuence the controlled glucose release proﬁles associate reduced glycemic response and insulin resistance ofdiabetes patients [172].
7. KGM versus other dietary ﬁbre
Dietary ﬁbre polysaccharides are of considerable physiologicalimportance [15]. The ﬁbre comprising plant cell wall polysaccharides and lignin (but not crude ﬁbre) that affects human large
bowel function is refereed as “dietary ﬁbre” [180]. The dietaryﬁbre acts in the colon depending on the extent to which they aredigested by colonic microﬂora and water holding capacity of ﬁbres[181–183]. The ﬁbres having less water holding capacity are extensively broken down and unable to provide support for stimulationof colonic microbial growth (e.g. cabbage ﬁbre). However, dietaryﬁbre polysaccharide such as KGM and other soluble ﬁbres (wheat,oats, minor millets, guar gum, pectin, and psyllium) remains largely
undigested and retains water in gut lumen [184,189].
The KGM ﬂour is used in the production of various types of foodsuch as noodles, rubber jelly, and certain food additives [92,93]. For
example, Japanese shirataki noodles, which are very low in calories,
are composed of KGM ﬂour [15]. It has been cultivated for centuries
in Japan and KGM is known to be used as a food storage polysaccharide. It is well known as a “hunger suppressant” because it produces
a feeling of fullness in stomach by forming a viscous solution thatprevents absorption of the nutrients in food. The mechanisms bywhich KGM is regarded as an excellent dietary ﬁbre include its
extraordinary high water holding capacity that forms high viscous

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S.S. Behera, R.C. Ray / International Journal of Biological Macromolecules 92 (2016) 942–956

Table 2
Applications of KGM.
Applications of KGM
Local and traditional uses of KGM
Food and food additives
Health applications
Blood glucose and cholesterol
Constipation and diarrhoea
Body weight control
Dietary ﬁbre and Prebiotic roles
Inﬂammatory bowel disease (IBD)
Intestinal micro-biota
Immune system

Responses/effects

Reference

1.Thickening and gelling agent
2. Improved texture[190][44,49]

Increased cholesterol binding
Stimulated gut transit, and controlled bowel movement
Approved body weight loss
Regulated gastrointestinal microﬂora counts
Positive effect on IBD
Increased beneﬁcial intestinal micro-biota
Modulated immune system[102–104]
[112]
[89]
[117]
[112]
[120]
[145]

solution in water [178]. It has been reported that one gram of KGM
can absorb up to 200 mL of water and has high viscosity at lowest
concentration of any known dietary ﬁbre [179].
8. Critical appraisal of KGM as a nutraceutical ﬁbre
The information presented in this review show the potential
nutritional and nutraceutical importance of KGM in improvementof health and well beings of human beings. KGM inﬂuences thedigestion of food in general [15]. Konjac is an affordable sourceof storage carbohydrates, starch, soluble sugars, protein, minerals,
crude ﬁbres, and health promoting fatty acids [3]. Scientiﬁc studies
have provided substantial evidences to support the actual/potential
beneﬁts of KGM in lowering the risks of various chronic diseases
particularly in reducing the insulin needs of people with type
II diabetes [76], altering lipid digestion [19,102] and cholesterol
absorption [93], inﬂuencing the bile acid metabolism [23] andprotecting against colonic cancer [86]. KGM has been widely considered as a dietry ﬁbre that has also nutraceutical properties [10].
Intake of foods containing high levels of cholesterol harms humanhealth. But, increase in the intake of KGM in diet is likely to mitigate
these ill effects [19].
However, information pertaining to the role of KGM in humandisease prevention and the mechanism of action are somewhat
scanty. This is probably due to the complex nature of disease etiology and multiple factors that have impacts on their occurrence[23].
9. Research gaps
The KGM is an attractive dietary ﬁbre that acts as a neutralhydro-colloid having signiﬁcant health functions [116]. It has been
widely used in food industry because of its good gelling, swellingand other properties [185]. In spite of several advantages of KGM,
their applications in food industry and pharmaceutical processes
limited due to highly perishable nature of fresh tuber. The tubers
are prone to many abiotic (physiological disorders and mechanical injuries) and biotic (diseases and pests) stresses [15]. Therefore,
there is a need of identifying effective storage methods to extend
the shelf life of the tuber.
Moreover, though KGM have been traditionally utilized for somany years, KGM and its derivatives still need to be well investigated compared to other well established polysaccharides suchas cellulose, starch, and chitosan. Thus, the challenge of understating its importance is being met an expansion of research in thebiomedical arena.

in pharmaceuticals particularly in treatment of type 2 diabetes(reducing blood glucose), obesity, regulating lipid metabolism,
diminution of constipation, treatment of hyperthyroidism, colorectal cancer, wound healing and antioxidant, antibiotics and prebiotic
activities.
Over the last few years a number of KGM-based food products,
food additives, and functional foods have been designed for humanconsumption. KGM and their derivatives have gained importanceas a new source of dietary ﬁbres and food ingredients. It has desirable physicochemical properties such as bland ﬂavour, swelling, gelformation capacity etc. KGM also has beneﬁcial properties such asincrease in viscosity and water binding capacity. It can be used also
in a wide variety of biomedical applications from wound dressing to restriction of the diffusion of glucose into the blood of
diabetic patients. Moreover, number of KGM-based biomedical systems, intended for administration for different purposes have been
invented. It is a better candidate for biomedical application as compare with synthetic polymers since it is both biocompatible andbiodegradable. KGM-based biomaterials are used for constipation
mitigation, control of blood glucose and cholesterol level (in caseof diabetes and obesity), as antioxidant, as anti-inﬂammatory, andbioadhesive supplements and medical implants.
KGM can improve the textural and rheological properties of foodproducts by regulating certain physico-chemical properties suchas solubility, viscosity and water holding capacity.Although, KGM
and its derivatives have been the focus of biomedical research in
the recent years but yet the number of studies are far less as compared to other polysaccharides such as cellulose, starch etc. Despite
the widespread consumption of konjac derived products in East andSouth East Asia, there has been limited research on the biology, processing and cultivation of the A. konjac species in the western world.
Further research on newer product development from KGM-based
polysaccharides need to be explored for potential applications infood, beverage, nutritional supplements as well as for biomedical
purposes.

Conﬂict of interest
None.

Financial support
None.

Acknowledgement
10. Conclusions and future perspective
From the ongoing discussion, it is evident that KGM is a very versatile biomaterial and dietary ﬁbre that can have wide applications

The authors would like to grateful National Institute of Technology, Rourkela 769008, India for providing technical support during
course of manuscript preparation.

S.S. Behera, R.C. Ray / International Journal of Biological Macromolecules 92 (2016) 942–956

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