Coenzyme Q and vitamin E need each other as antioxidants

Both vitamin E and coenzyme Q possess distinct lipoprotective antioxidant properties in biological membranes. Their combined antioxidant activity, however, is markedly synergistic when both are present together. While it is likely that vitamin E represents the initial chain-breaking antioxidant during lipid peroxidation, both fully reduced CoQH(2) (ubiquinol) and semireduced CoQH(.) (ubisemiquinone) appear to efficiently recycle the resultant vitamin E phenoxyl radical back to its biologically active reduced form. We describe and support a potential kinetic mechanism whereby vitamin E and coenzyme Q interact in such a way as to usurp the prooxidant effects of O-2(-.). Physical interactions of vitamin E and coenzyme Q within the environment of the membrane lipid bilayer facilitate the recycling of vitamin E by ubisemiquinone and ubiquinol. Lastly, data are linked into a catalytic cycle that serves to connect normal electron transport mechanisms within biological membranes to the maintenance of lipoprotective antioxidant mechanisms.