Comparative theoretical researches on the anti-oxidant activity of δ-viniferin and ε-viniferin

•FMO analysis suggests that δ-viniferin is a more potent anti-oxidant than ε-viniferin.•HAT should be the favored mechanism in the gas phase and non-polar solvents, while SPLET would be the most preferred reaction pathway in the polar solvents.•12’-OH of δ-viniferin and 12-OH of ε-viniferin should be the most reactive site for scavenging radicals. Viniferin, the dimer of resveratrol, is an important natural product class with anti-oxidant activities. δ-viniferin and ε-viniferin are two different isomers of viniferin. In this context, a systematic theoretical study by density functional theory (DFT) calculations is carried out on these two isomers’ radical scavenging activity, which focuses on the thermodynamically preferred mechanism, anti-oxidant sites, and anti-oxidant activity sequence of δ-viniferin and ε-viniferin. Three radical scavenging mechanisms named hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were discussed. The anti-oxidative capacities of δ-viniferin and ε-viniferin in the gas phase and solvents were elucidated by comparing the thermodynamic parameters such as bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE). The computational results showed that δ-viniferin is a more potent anti-oxidant than ε-viniferin. The obtained results may have some important implications for better understanding the relationship between structure and anti-oxidant activity, designing more active anti-oxidants, and providing theoretical guidance for developing and utilizing resveratrol derivatives. [Display omitted]