Quantum mechanical study of antioxidative ability and antioxidative mechanism of rutin (vitamin P) in solution.

A quantum mechanical approach has been used to shed light on the antioxidative mechanism for scavenging hydroxyl radicals (()OH) and superoxide radicals (O2-) by rutin in the solution phase. Density-functional theory (DFT) using B(3)LYP and UB(3)LYP functional and split-valance 6-311+G(∗∗) basis sets were used to optimize rutin and its different radical forms. Analysis of the theoretical bond dissociation enthalpy (BDE) values for all OH sites of rutin in solution clearly shows the importance of the B-ring and the 3'-OH and 4'-OH groups in the antioxidant activity. We have also investigated the spin density of the radicals to determine the delocalization possibilities. The results of the calculations showed that the oxidation of rutin by both the hydroxyl radical and superoxide radical is an exothermic reaction. In all calculations solvent effects were considered using a polarized continuum model (PCM).