title: Antioxidant activity of trans-resveratrol toward hydroxyl and hydroperoxyl radicals: a quantum chemical and computational kinetics study.
abstract: In this work, we have carried out a systematic study of the antioxidant activity of trans-resveratrol toward hydroxyl ((•)OH) and hydroperoxyl ((•)OOH) radicals in aqueous simulated media using density functional quantum chemistry and computational kinetics methods. All possible mechanisms have been considered: hydrogen atom transfer (HAT), proton-coupled electron transfer (PCET), sequential electron proton transfer (SEPT), and radical adduct formation (RAF). Rate constants have been calculated using conventional transition state theory in conjunction with the Collins-Kimball theory. Branching ratios for the different paths contributing to the overall reaction, at 298 K, are reported. For the global reactivity of trans-resveratrol toward (•)OH radicals, in water at physiological pH, the main mechanism of reaction is proposed to be the sequential electron proton transfer (SEPT). However, we show that trans-resveratrol always reacts with (•)OH radicals at a rate that is diffusion-controlled, independent of the reaction pathway. This explains why trans-resveratrol is an excellent but very unselective (•)OH radical scavenger that provides antioxidant protection to the cell. Reaction between trans-resveratrol and the hydroperoxyl radical occurs only by phenolic hydrogen abstraction. The total rate coefficient is predicted to be 1.42 × 10(5) M(-1) s(-1), which is much smaller than the ones for reactions of trans-resveratrol with (•)OH radicals, but still important. Since the (•)OOH half-life time is several orders larger than the one of the (•)OH radical, it should contribute significantly to trans-resveratrol oxidation in aqueous biological media. Thus, trans-resveratrol may act as an efficient (•)OOH, and also presumably (•)OOR, radical scavenger.
authors.affiliation: Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, 02200 México DF, Mexico. ciuga@xanum.uam.mx
authors.forename: Cristina
authors.initials: C
authors.lastname: Iuga
authors.forename: J Raúl
authors.initials: JR
authors.lastname: Alvarez-Idaboy
authors.forename: Nino
authors.initials: N
authors.lastname: Russo
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D016166:Free Radical Scavengers; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry*; D011789:Quantum Theory; D000077185:Resveratrol; D013267:Stilbenes / Q000737:chemistry* / Q000494:pharmacology*; D014867:Water
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D010545:Peroxides; D013267:Stilbenes; D014867:Water; D017665:Hydroxyl Radical; D000077185:Resveratrol