Résumé:
Allium Cepa known under the vernacular name "البصل", is a plant of the Amaryllidaceae family used in traditional Algerian medicine for its important properties. Antioxidants are chemi- cals that are naturally present in certain foods., these substances help to protect the body's cells. The present work focused on the phytochemical study of the aqueous extract from Allium Cepa bulbs and the evaluation, in vitro, of its antioxidant activity as well as the dosage of its polyphenol and flavonoid content. The quantitative estimate of polyphenols and flavonoids is determined by colorimetric methods using Folin Ciocalteu and Aluminum Chloride, respectively. The antioxidant properties were evaluated by the test of 2,2-diphenyl-1-picryl-hydrazyl (DPPH), 2,2'-azino-bis (3- ethylbenzothiazoline-6-sulphonic acid) (ABTS) and the potency FRAP iron reducer. The phyto- chemical results show the presence of certain biologically active molecules such as flavonoids, tannins, catechic tannins, anthocyanins, proteins, reducing compounds, sterols and triterpenes, gen- ins, oses and holosides, heterosides (C-heterosides, cardiac glycosides, O-heterosides with reduced genin), flavanones, flavans, leuco anthocyanins and carotenoids, in the bulb of Allium Cepa and an absence of certain compounds such as mucilages, sapo- nosides, alkaloids, narcotics, free anthra- quinones, cyanogenic glycosides and O-heterosides, coumarins, catechins, pro anthocyanins, fla- vones, flavanols, flavonoid glycosides, isoflavones, dihydrochalcones, aurones , gallic tannins and catechols. The polyphenol and flavonoid assay results suggest that Allium Cepa extract is rich in these secondary metabolites. In addition, it reveals an interesting antioxidant activity, where the bulb extract has an excellent scavenger effect against the DPPH free radical, and the ABTS test. The results of the ABTS test demonstrated that the Allium Cepa extract has an inhibition percentage of 74.37%. The results of the DPPH test demonstrated that the Allium Cepa extract has an inhibition percentage equal to 69.33% with an IC50=1.32 mg/ml. In addition, the FRAP method shows that this extract has a strong reducing power with an IC50 of 0.21±0.1mg/ml. Allium Cepa is a poten- tially promising source of natural antioxidants and can be used to prevent the onset of diseases related to oxidative stress.
