Abstract
The current study aimed to identify the chemical constituents of Chenopodium ambrosioides (Linn.), and the assessment of the in vitro antioxidant activity of the different extracts and pure isolates. Methods: The antioxidant activity was estimated via free radical scavenging and phosphomolybdenum assays. Structure elucidation of pure compounds was achieved via UV, IR, H-1 & C-13-NMR, H-1-H-1 COSY, HMQC, and HMBC, spectroscopy. Bioassay-guided fractionation and isolation of the n-butanol fraction led to the isolation of a new kaempferol glycoside namely; kaempferol 3-O-alpha-L-C-1(4)-rhamnosyl-(1''' -> 2'')-beta-D-C-4(1)-xylopyranoside (1), together with five known compounds identified as; kaempferol 3-O-alpha-L-C-1(4)-rhamnopyranoside (afzelin) (2), kaempferol 7-O-alpha-L-C-1(4)- rhamnopyranoside (3), caffeic acid (4), 1,2-benzopyrone (coumarin) (5), and kaempferol (6). Compound (1) showed in vitro antioxidant activity of SC50 12.45 mu g/ml, compared to ascorbic acid (AA) with SC50 of 7.50 mu g/ml. It can conclude that the leaves of C. ambrosioides can be used as promising natural antioxidant agents.