A comparative study on the antioxidant properties of bractein and cernuoside by the DFT method

Abstract

Density functional theory was employed to investigate the molecular properties of two flavonoids, bractein and cernuoside, that serve as antioxidants. The B3LYP/6-311G** protocol was used for all computations. Investigations were performed in the gas phase and in two solvents with different polarity (water and benzene); the present work was devoted mainly to the determination of the O–H bond dissociation enthalpies and the ionization potentials of the examined compounds, since these quantities represent the most important parameters on which biological activity can be rationalized. The rotational energy of pyrogallol and catechol moieties together with highest occupied molecular orbital–lowest unoccupied molecular orbital and dipole moment analysis are reported for the two flavonoids. The present analysis also includes the spin density distribution for the radicals formed after H atom removal on each OH site of both flavonoids. The theoretical bond dissociation enthalpy values for these systems follow the same trend in gas and solvent phases. On the basis of computed bond dissociation enthalpy and ionization potential values, the most reactive system that is able to transfer an H-atom and electron transfer mechanism is found to be bractein followed by cernuoside. All these results suggest bractein to be a potential antioxidant similar to quercetin. .