The antioxidative activity of piceatannol and its different derivatives: Antioxidative mechanism analysis.

The naturally occurring stilbenes piceatannol and its derivatives are excellent antioxidants. In this work, the antioxidative activities of piceatannol and different piceatannol derivatives have been investigated using the density functional theory (DFT) method based on three widely accepted radical scavenging mechanisms, namely, the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). The gas and four solvent phases, namely, bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA) and electron transfer enthalpy (ETE), related to these mechanisms were calculated to elucidate the antioxidative capacities of the investigated compounds. This work focuses specifically on the thermodynamically preferred mechanism, antioxidative site and antioxidative activity order of the investigated stilbenes. The substituted effects of the methyl group and prenyl group on the chemical properties of the remaining OH and CH groups are also analysed. This work confirms the vital role of the OH and CH groups on free radical scavenging of piceatannol and its derivatives.