Theoretical study of antioxidative ability and antioxidative mechanism of norathyriol in solution

A quantum mechanical approach has been used to shed light on the antioxidative mechanism for scavenging (OOH)-O-center dot and (OH)-O-center dot radicals by norathyriol in the solution phase. Density functional theory (DFT) calculations at the B3LYP and UB3LYP/6-311+G(d,p) level are used to optimize norathyriol and its different radical forms. Analysis of the theoretical bond dissociation enthalpy (BDE) values for all OH sites of norathyriol in solution clearly shows the importance of the B-ring and the 6-OH and 7-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 show that the oxidation of norathyriol by both the (OOH)-O-center dot and (OH)-O-center dot radical is an exothermic reaction. In all calculations solvent effects are considered using a polarized continuum model (PCM). (C) 2013 Elsevier B.V. All rights reserved