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

Viniferin, the dimer of resveratrol, is an important natural product class with anti-oxidant activities. delta-viniferin and epsilon-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 scav-enging activity, which focuses on the thermodynamically preferred mechanism, anti-oxidant sites, and anti-oxidant activity sequence of delta-viniferin and epsilon-viniferin. Three radical scavenging mechanisms named hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequen-tial proton loss electron transfer (SPLET) were discussed. The anti-oxidative capacities of delta-viniferin and epsilon-viniferin in the gas phase and solvents were elucidated by comparing the thermodynamic param-eters 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 delta-viniferin is a more potent anti-oxidant than s-viniferin. The obtained results may have some important implications for better understanding the relationship between structure and anti-oxidant activity, de-signing more active anti-oxidants, and providing theoretical guidance for developing and utilizing resver-atrol derivatives. (C) 2021 Elsevier B.V. All rights reserved.