Antioxidant Properties of Catechin and Its 3′O-Α-glucoside: Insights from Computational Chemistry Calculations

Density functional theory (DFT) calculations were used to investigate the conformational landscape of catechin and one of its main glucoside derivative (catechin-3 ' O- alpha - glucopyranoside), and to determine the corresponding antioxidant properties. These investigations were carried out in benzene and water using the SMD universal continuum solvation model. Both properties were found to be significantly affected. The structures are characterized in both solvents by strong intramolecular hydrogen bonds (IMHB). In an apolar environment, Hydrogen Atom Transfer (HAT) is by far favored whereas in water the Sequential Proton Loss Electron Transfer (SPLET) mechanism is strongly preferred. In benzene, the catechin fragment has the best antioxidant character (from 27 kJ/mole) whereas in polar surroundings, the glucoside derivative has a slightly better antiradical activity (from 5 kJ/mole). Our results confirm the key role of the 3 ' -OH and 4 ' -OH groups of the catechole ring in these properties.