A DMol3 study on the reaction between trans-resveratrol and hydroperoxyl radical: Dissimilarity of antioxidant activity among O-H groups of trans-resveratrol

The DMol3 calculations, based on the density functional theory (DFT), have been used to study the structure-activity relationship of trans-resveratrol in the reaction of scavenging free radicals. The geometries of trans-resveratrol and its three phenoxy radicals were obtained at the Generalized Gradient Approximation (GGA) level, with the spin unrestricted approach and BLYP/DND method. Three possible reactions of scavenging hydroperoxyl radicals, in terms of H-atom-transfer mechanism, were designed. The transition state for each reaction was determined, and the intrinsic reaction coordinate was analyzed. The activation energy and thermodynamic state functions were calculated. The differences of the BDE and structure properties of stationary points show that 4′-radical is stabler and 4′-hydroxyl is more reactive. And the results also show that the reaction of 4′-hydroxyl scavenging hydroperoxyl radicals is more competitive in view of thermodynamics and kinetics. Thus, the dissimilarity of antioxidant activity among O-H groups of trans-resveratrol, which had been reported by many experimental studies, is explained.