Isolation and structure elucidation of natural antioxidants from leaves of Rauvolfia beddomethe –an endemic/endangered medicinal plant from SouthWestern Ghats of India

Phytochemical and antioxidant activity studies of the leaves of Rauovlofia beddomei Hook. (Apocyanaceae) have been carried out. The ethyl acetate fraction of methanol extract yielded five compounds (1 – 5) identified as flavonoids: (1) kaempferol, (2) kaempferol-3-O-D-glucoside, (3) quercetin, (4) apigenin-3-O-D-glucoside, and (5) apigenin-7-O-neohespiridoside. The structures of compounds 1 – 5 were elucidated on the basis of spectroscopic analysis. The antioxidant properties of the isolated compounds were evaluated by measuring their ability to scavenge DPPH radicals and superoxide anions, to inhibit xanthine oxidase (XOD) activity, and to inhibit lipid peroxidation (LPO) in a liposome model system. Compound 3 was a strong scavenger of DPPH and superoxide anion radicals, inhibitor of XOD activity, and potent LPO inhibitor, showing some structure – activity relationships.