Direct observation of a free radical interaction between vitamin E and vitamin C

Abstract

VITAMIN E (α-tocopherol) and vitamin C (ascorbic acid) react rapidly with organic free radicals, and it is widely accepted that the antioxidant properties of these compounds are responsible in part for their biological activity^1–5. Tissue vitamin C levels are often considerably greater than those of vitamin E, for example in liver the values are approximately 2 mM and 0.02 mM, respectively. Nevertheless, vitamin E is considerably more lipophilic than vitamin C, and in biomembranes has been found to be the more potent antioxidant, particularly with respect to lipid peroxidation; penetration to a precise site in the membrane may be an important feature of the protection against highly reactive radicals⁶. Tappel has suggested that the two vitamins act synergistically, vitamin E acting as the primary antioxidant and the resulting vitamin E radical then reacting with vitamin C to regenerate vitamin E⁷. We now report direct observation of this interaction, which we feel may be an important feature in the maintenance of vitamin E levels in tissues.