Radical-induced oxidation of trans-resveratrol

Abstract

trans-Resveratrol (RVT) (3,5,4′-trihydroxystilbene), a polyphenolic constituent of red wine, is thought to be beneficial in reducing the incidence of cardiovascular diseases, partly via its antioxidant properties. However, the mechanism of action by which trans-resveratrol displays its antioxidant effect has not been totally unravelled. This study aimed at establishing a comprehensive scheme of the reaction mechanisms of the direct scavenging of HO and O2− radicals generated by water gamma radiolysis. Aerated aqueous solutions of trans-RVT (from 10 to 100μmolL−1) were irradiated with increasing radiation doses (from 25 to 400Gy) and further analyzed by UV–visible absorption spectrophotometry for detection of trans-RVT oxidation products. Separation and quantification of RVT and its four oxidation products previously identified by mass spectrometry, i.e., piceatannol (PCT), 3,5-dihydroxybenzoic acid (3,5-DHBA), 3,5-dihydroxybenzaldehyde (3,5-DHB) and para-hydroxybenzaldehyde (PHB), were performed by HPLC/UV–visible spectrophotometry. Determination of the radiolytic yields of trans-RVT consumption and oxidation product formation has allowed us to establish balance between trans-RVT disappearance and the sum of oxidation products formation. Under our conditions, O2− radicals seemed to poorly initiate oxidation of trans-RVT, whereas the latter, whatever its initial concentration, quantitatively reacted with HO radicals, via a dismutation mechanism. Two reaction pathways involving HO-induced trans-RVT primary radicals have been proposed to explain the formation of the oxidation end-products of trans-RVT.