Butein, a more effective antioxidant than α-tocopherol

The geometries of the butein and its radicals have been optimized by using the density functional theory method. In order to analyze the antioxidant properties of the butein, the ionization potential (IP), the bond dissociation energy (BDE), the highest occupied molecular orbital (HOMO), and the spin density have been calculated. The calculated results reveal that the antioxidant mechanism of the butein corresponds to its H-atom transfer, and that the B-ring of the butein has a strong hydrogen-donated ability and the 4-OH is the active site with the lowest BDE. The calculated results also show that the butein can serve as a powerful antioxidant against DPPH radical, and that the reaction mechanism was described in detail. On the basis of the calculated BDE, one finds that the butein is a more effective antioxidant than the α-tocopherol.