# Potential Role of Plant Extracts and Phytochemicals Against Foodborne Pathogens
## 5 Plant Extracts and Phytochemicals against Parasites Causing Foodborne Diseases
### Giardia lambiia
The in vivo study revealed that PR administration in doses of 225, 450 and 900 mg/kg exhibited 62%, 79% and 98% parasitic clearance, respectively. Moreover, PR significantly augmented the macrophage phagocytic activity and macrophage migration index at all the tested doses. As the PR formulation is inactive against the parasite in vitro, so it was proposed that the formulation may mediate its anti-giardial activity through boosting of host immune system and thereby increasing clearance mechanisms [216]. To further explore the clinical significance of PR formulation, [PERSON] et al. extended the study and included fifty human subjects with all signs and symptoms of giardiasis including cysts and Giardia trophozoites in the stool samples. The subjects were divided into two groups; the treated group was maintained on PR (1 g T.D.S) for fifteen days, whereas the second group served as a placebo control. After the completion of therapy, stool samples were analyzed for _G. lamblia_, frequency of diarrhea and mucous content of the stool. In the treated group, 92% inhibition of _Giardia_ and a significant decline in diarrhea and mucous were observed. A boost in the cell-mediated immune system indicated by a decline in leukocyte migration was also observed [217]. In a study, [PERSON] et al. evaluated the giardicidal potential of propolis in 136 subjects with well-known symptoms of giardiasis. In the five days' trials, propolis was administered in 20, 30% solutions (adults) and 10% solution (children) and duodenal aspirates were evaluated for giardicidal activity. Results of the study revealed 60% giardicidal activity for 30% solution and 40% giardicidal activity for 20% solution in adults whereas, 52% giardicidal activity was observed in children after administration of 10% solution. The standard drug, tinidazole exhibited a 40% efficacy [218]. Several studies have confirmed the efficacy of berberine and berberine rich plants including _Coptis chinensis_. [PERSON], _Berberis vulgaris_ L., _Berberis aquifolium_ [PERSON], _Berberis aristata_ DC. and _Hydrastis canadensis_ L. in the management of gastrointestinal disorders like parasitic infestation and diarhaea [219; 220]. Berberine is highly effective against Giardia trophozoites and mediates its beneficial effects via morphologic changes in the trophozoites including changes in the shape of vacuoles, trophozoites swelling and deposition of glycogen deposits [221]. Berberine hydrochloride at a dose of 5 mg/kg showed a 68% decline in the stool-_Giardia_ content and a significant decline in giardiasis symptoms in a clinical study [222]. In a clinical trial, berberine administered in doses of 5, 10 mg/kg for 5-10 days showed a 47%, 55%, 68% and 90% decline in the Giardia content in all the treated groups of children. The standard drugs, furazolidone and metronidazoleze exhibited a 92% and 95% efficiency against _Giardia_[223]. In vitro studies have revealed high efficacy of crude extracts from these plants in comparison to pure berberine, which can be attributed to the synergistic interactions of berberine with other isoquinoline alkaloids present in these plants [224]. Natural flavonoids including epicatechin, quercetin, epigallocatechin, apigenin and kempfer, which are abundant in several natural products like _Quercus robur_ L., _Hamamelis virginiana_ L. and _Croton lechleri_ Mull.Arg. are extensively reported for giardicidal potentials [225; 226; 227]. In a study, flavonoids and tannins rich plants including _Origanum vulgare_ L., _Psidium guajava_ L., _Mangifera indica_ L. and _Plantago major_ L. showed high anti-giardial activity in comparison to the standard drug, tinidazole [228]. [PERSON] et al. reported the antigiardial activity of flavonoids isolated from _Geranium mexicanum_ [PERSON], _Helanthemum glomeratum_ (Lag.) Lag. ex Dunal, _Cuphea pinetorum_ [PERSON] and _Rubus corifolius_ [PERSON]. Among the isolated compounds, kempfer, tiliroside and epicatechin exhibited IC\({}_{50}\) values of 2.057, 1.429 and 0.072 umol/kg, respectively against _G. lamblia_[229].