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.