UBIQUINOL - AN ENDOGENOUS ANTIOXIDANT IN AEROBIC ORGANISMS

Ubiquinone (coenzyme Q), in addition to its function as an electron an d proton carrier in mitochondrial and bacterial electron transport lin ked to ATP synthesis, acts in its reduced form (ubiquinol) as an antio xidant, preventing the initiation and/or propagation of lipid peroxida tion in biological membranes and in serum low-density lipoprotein. The antioxidant activity of ubiquinol is independent of the effect of vit amin E, which acts as a chain-breaking antioxidant inhibiting the prop agation of lipid peroxidation. In addition, ubiquinol can efficiently sustain the effect of vitamin E by regenerating the vitamin from the t ocopheroxyl radical, which otherwise must rely on water-soluble agents such as ascorbate (vitamin C). Ubiquinol is the only known lipid-solu ble antioxidant that animal cells can synthesize de novo, and for whic h there exist enzymic mechanisms that can regenerate the antioxidant f rom its oxidized form resulting from its inhibitory effect of lipid pe roxidation. These features, together with its high degree of hydrophob icity and its widespread occurrence in biological membranes and in low -density lipoprotein, suggest an important role of ubiquinol in cellul ar defense against oxidative damage. Degenerative diseases and aging m ay be manifestations of a decreased capacity to maintain adequate ubiq uinol levels.