Improvement of antioxidative activity of resveratrol by elongating conjugated chain: A DFT theoretical study

Elongation of the conjugated chain of resveratrol has been proved to be an effective strategy to further improve its antioxidative capacity and radical scavenging ability. In this work, quantum chemical calculations based on density functional theory have been employed at B3LYP/6-311G(d,p) level of theory to study the influence of the conjugated chain length on equilibrium geometries and properties of relevant species. Our results show elongation of conjugated chain significantly decreases 4'-OH bond dissociation enthalpy (BDE), ionization potential (IP) and proton affinities (PAs) of phenolate ions in gas phase. In aqueous solution 4'-OH BDE, IP are lower as compared to that i gas phase, for PAs of phenolate ions almost no change is induced, but significant decrease in electron transfer enthalpy (ETE) is presented. These indicate that longer conjugated chain is favorable for the radical scavenging capacity and antioxidative activity. In addition, stable s-cis conformers of long chain reservatrol analogs are found to be more favorable for production of phenoxyl radicals and cation radicals as compared to trans conformers, with concomitant enhancement of the antioxidative activity. (C) 2013 Elsevier B.V. All rights reserved.