STILBENE GLYCOSIDES FROM THE ROOTS OF POLYGONUM MULTIFLORUM THUNB AND THEIR IN VITRO ANTIOXIDANT ACTIVITIES

ABSTRACT Stilbene glycosides (SGs) were isolated from the ethanol extract of the roots of Polygonum multiflorum (PM) Thunb. Three samples were obtained: the crude extract, the fraction separated by macroporous resin and the pure crystal 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside. The structure of the crystals was determined by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectrometry. The antioxidant activities of three samples containing SG were evaluated using different antioxidant tests, including free radical scavenging, superoxide anion scavenging, hydroxyl radical scavenging and the inhibition of lipid peroxide formation in organs (liver, heart and brain) of a rat in vitro. These various antioxidant activities were compared with those of resveratrol, which is structurally similar to SG of PM. The results indicated that all three samples showed antioxidant activities, with the pure SG being the most efficient one. The IC50 values for 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside were 8.06, 2.75 and 0.57 µg/mL for 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) scavenging, hydroxyl radical scavenging and superoxide anion scavenging, respectively. The IC50 values for 2,3,5,4′‐tetrahydroxystilbene 2‐O‐β‐D‐glucopyranoside in inhibiting lipid peroxide formation in liver, heart and brain were 13.68, 16.34 and 17.62 µg/mL, respectively. It was shown that SG from PM has a better antioxidant potency than that of resveratrol.