Efficiency and Mechanism of the Antioxidant Action of trans-Resveratrol and Its Analogues in the Radical Liposome Oxidation

trans-Resveratrol (trans-3,5,4′-trihydroxystilbene) is a nonflavonoid polyphenol reported to exert different biological activities, among them inhibition of the lipid peroxidation, scavenging of the free radicals, inhibition of the platelet aggregation, and anticancer activity as the most important. In order to enlighten the radical-scavenging mechanism of trans-resveratrol, stationary γ-radiolytic experiments in liposomes and pulse radiolytic experiments in aqueous solutions were performed. Applying the stationary γ-radiolysis together with the subsequent product analysis, reactions of lipid peroxyl radicals, LOO•, with trans-resveratrol and other natural antioxidants were investigated. It was found that trans-resveratrol was a better radical scavenger than vitamins E and C but similar to the flavonoids epicatechin and quercetin. The comparison of the radical-scavenging effects of trans-resveratrol and its analogues trans-4-hydroxystilbene and trans-3,5-dihydroxystilbene revealed that trans-resveratrol and trans-4-hydroxystilbene showed almost the same effect and were more efficient than trans-3,5-dihydroxystilbene. These findings indicate greater radical-scavenging activity of trans-resveratrols para-hydroxyl group than its meta-hydroxyl groups. Using the pulse radiolysis, reactions of trans-resveratrol and its analogues with trichloromethylperoxyl radicals, CCl3OO•, were studied. Spectral and kinetic properties of the observed transients showed great similarity between trans-resveratrol and trans-4-hydroxystilbene which seems to confirm that para-hydroxyl group of trans-resveratrol scavenges free radicals more effectively than its meta-hydroxyl groups.