# Potential Role of Plant Extracts and Phytochemicals Against Foodborne Pathogens
## 5 Plant Extracts and Phytochemicals against Parasites Causing Foodborne Diseases  
### Giardia lambiia  
Giardiasis is a human parasitic infection most commonly transmitted through the ingestion of infected food and is associated with significant morbidity [206]. The most common cause of giardiasis is the protozoan, _Giardia lamblia_ commonly called _G. intestinalis_ and _G. duodenalis_. Several treatment strategies are devised for its eradication which includes nutritional intervention, ingestion of probiotics and phytotherapeutic agents [207]. Several natural products including _Allium sativum_, berberine and flavonoid-rich herbs, _Piper longum_ L., _Butea monosperma_ (Lam.) Taub. and various isolated compounds have been found effective in the eradication of giardiasis [208; 209]. Natural products based therapeutics play a significant role in the treatment and management of giardiasis, mediated through eradication of parasite and thus relieving the unwanted symptoms of infection. Several herbs are extensively reported for their effectiveness in _Giardia_ infections; _Allium sativum_ is a well-known household remedy against numerous human diseases including microbial and parasitic infections [210]. In a study, [PERSON] et al. reported the anti-giardial potentials of crude _A. sativum_ and its isolated compounds; A. _sativium_ crude extract exhibited IC\({}_{50}\) of 0.3-mg/mL against _Giardia intestinalis_, whereas, the isolated compounds allyl mercaptan, diallyl disulfide, diallyl sulfide, allyl alcohol and dimethyl disulfide showed IC\({}_{50}\) values of 0.037, 0.1, 1.3, 0.007 and 0.2 mg/mL, respectively [33]. Furthermore, the incubation of _Giardia_ trophozoites in the presence of whole _A. sativa_ exhibited considerable decline in the parasite motility, flagellar movement and ultimate swelling of the trophozoite. The mechanisms underlying these events involve the loss of osmoregulation of parasite and loss of transmembrane electrochemical gradient. Microscopic studies revealed morphologic changes in the ventral disc of the parasite which can be responsible for its inability to attached to its host cell [33]. In another clinical study, [PERSON] and [PERSON] administered fresh _A. sativum_ distilled water extract (5 mL) or 0.6 mg commercially available capsules to 26 children infected with _G. lamblia_ for three days and observed its beneficial effects against giardiasis [211]. The symptoms of giardiasis were effectively subsided in all the groups of children with thirty-six hours of therapy and the stool examination revealed complete eradication of parasite [211]. Allicin isolated from _A. sativum_ is reported to mediate its action against the parasite via inhibition of giardia's cysteine proteases and inhibition of products responsible for unwanted symptoms of giardiasis [212; 213]. Moreover, _A. sativa_ also increases the mucosal nitric oxide (NO) production via stimulation of nitric oxide synthase, which subsequently increases the liberation of NO from enterocytes and exhibits direct giradicidal effects [33]. _Piper longum_ L. is a well-known folk medicine for the treatment of gastrointestinal disorders and helminthesis [214]. In a study, [PERSON] et al. investigated the giradicidal actions of crude extracts of _P. longum_. Treatment with crude ethanolic extract (125 mg/mL) and aqueous extracts (250 mg/mL) showed 100% lethality against _Giardia lamblia_. In an animal model of giardiasis, _P. longum_ crude ethanolic extract, aqueous extract and fruit powder at doses of 250, 450 and 900 mg/kg, respectively significantly (75%) diminished the live trophozoites count in the intestinal mouse aspirates after five days of therapy [215]. The two important gastoprotective herbs including _Piper longum_ and _Butea monosperma_ have been combined in a traditional herbal formulation called Pippali rasayana (PR). This formulation is very famous in folk medicine for the treatment of helminthesis and chronic dysentery. In a study, [PERSON] et al. reported the anti-giardial effects of PR formulation in an animal model.