Analyse phytochimique et étude in vitro de l’effet antioxydant de deux plantes médicinales Allium Sativum et Allium Cepa

Abstract

This research work represents a qualitative and quantitative study on a species of Allium Sativum and Allium Cepa. the preliminary tests used are: Phytochemical screening by coloring tests (qualitative tests) and quantitative spectrophotometry tests Ciocalteu madness test to quantify the content of total polyphenols, the Aluminum trichloride method to quantify total flavonoids. Thus, the evaluation of the antioxidant activity using the methods of oxidation of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, the ABTS test (2, 2'-azynobis [3-ethylbenzothiazoline- 6-sulfonic acid]) and the antioxidant capacity of ferric iron (FRAP); with ascorbic acid, Trolox and the standard Iron Sulfate (FeSO4)7 H20 as successive synthetic references. Quantification tests are based on ultraviolet visible spectroscopy. This study focused on the different chemical compositions of plants. The quantity of total polyphenols of the aqueous extracts of Allium Cepa, Allium Sativum and of the mixture (Allium Cepa + Allium Sativum) Corresponding were reported as the equivalent of one milligram of the standard used per gram of freeze-dried extract respectively 100.64 ±0.31 mgEAG/g, 109.88±1.67 mgEAG/g and 105.51±0.83. The results show that the amount of total flavonoids in mg equivalent of quercetin per gram of extract are 11.24 ± 0.3 mg EQ / g; 18.12 ± 0.03 mg EQ / g and 17.05 ± 0. 34mg EQ/g. These obtaine results show the richness of the extracts in flavonoids and total phenols. The evaluation of the antioxidant power showed that the aqueous extracts of Allium Cepa, Allium Sativum and the Blend (Allium Cepa + Allium Sativum) have a very high antioxidant power at 0.5mg/ml respectively for the three methods: IDPPH=69.33±0.44%, IDPPH=81.76±0.72% and IDPPH=81.35±0.19%; IABTS=74.37±1.25%, IABTS=89.69±0.11% and IABTS=89.33±0.39%; AFRAP=0.79±0.08%, AFRAP=0.88±0.02% and AFRAP=0.87±0.08%. Moreover, a strong correlation was shown between DPPH, ABTS and FRAP; the highest correlations are (r=0.989 and r=0.987) successive. As a result, this study confirms, scientifically, that the bulbs of garlic "Allium Sativum", onion "Allium Cepa" are a very good source of antioxidant substances, and therefore very beneficial to human health.