Antioxidant Flavone C-Biosides From The Aerial Parts Of Alternanthera Pungens
From the 2-butanone fraction derived out of the aqueous alcoholic extract of the fresh aerial parts of Alternanthera pungens, three C-glycoflavones, vitexin (1), isovitexin (2) and orientin (3) and an yellow solid composed of their 2"-O-Î²-D glucopyranosides (4-6) were isolated and characterised. Fully assigned sets of proton and carbon resonances, based on detailed 1D and 2D NMR measurements, including 1H COSY, HMQC and HMBC experiments, enabled the deduction of definitive evidence for the C- and the O-glycosidic linkages of the three biosides. Antioxidant potential of these six compounds was evaluated using two different assays, namely, the Trolox equivalent antioxidant capacity and the coupled oxidation of B-carotene and linoleic acid (autoxidation) assays. Compounds 3 and 6 were fairly active while the others were mildly active in both the assays.