Reduced Coenzyme Q10：Ubiquinol-10 (CoQ10H2), the reduced form of Coenzyme Q10, is a powerful antioxidant for lipids in plasma and lipoproteins. It has been suggested that endogenous CoQ10H2 also exerts a protective role even towards DNA oxidation mediated by lipid peroxidation. Although the antioxidant activity of coenzyme Q10 is ascribed mainly to CoQ10H2, a role for ubiquinone-10 (the oxidised form, CoQ10), appears feasible if appropriate reducing systems are present.