2,2-Diphenyl-1-picrylhydrazyl radical-scavenging active components from Polygonum multiflorum thunb.

An activity-directed fractionation and purification process was used to identify the antioxidative components of Polygonum multiflorum Thunb. (PM). Dried root of PM was extracted with 95% ethanol and then separated into water, ethyl acetate, and hexane fractions. Among these only the ethyl acetate phase showed strong antioxidant activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test when compared with water and hexane phases. The ethyl acetate fraction was then subjected to separation and purification using silica gel column chromatography and Sephadex LH-20 chromatography. Three compounds showing strong antioxidant activity were identified by spectral methods ((1)H NMR, (13)C NMR, and MS) and by comparison with authentic samples to be gallic acid, catechin, and 2,3,5, 4'-tetrahydroxystilbene 2-O-beta-D-glucopyranoside.