The antioxidative potential of procyanidin B1: DFT (density functional theory) and docking approaches.

Procyanidin B1 is one of the natural dimeric flavonoids. It has established a great role in antioxidative activity. In the current study, we wish to provide crucial information on its antioxidative action by the DFT computational and docking approaches. From point of thermodynamic view, at the M062X/6-311G(d,p) level, the HAT (hydrogen atom transfer) and SPL-ET (sequential proton loss-electron transfer) are principal antioxidative routes of this compound in gas and methanol, respectively. OH groups of two phenyl rings of this molecule are likely to be the best antiradical sites. In the kinetics of the interactions with HOO• radicals, OH groups of phenyl rings have also generated the best ΔG# (Gibbs free energy of activation) and rate constant K. The antioxidative action of procyanidin B1 is further confirmed by its chelation to metal ions, in which complex formation with Cu2+ having lower binding energy is more stable than complex formation with Zn2+. Docking study revealed that the antioxidative activity of procyanidin B1 involved human tyrosinase enzyme inhibition through interaction with essential residues, focusing on the OH groups of two phenyl rings.