VITAMIN E AND FREE RADICAL PEROXIDATION OF LIPIDS *

Several broad lines of scientific evidence showing that vitamin E functions as a lipid antioxidant, inhibiting the destructive peroxidation of polyunsaturated lipids, have been presented in recent reviews.'-Q Further, the function of vitamin E is a very broad topic, study of which can be based in part on knowledge of other lipid antioxidant reactions and interrelationships. Also, the reactions of and the damage caused by free radical peroxidation of lipids are complex topics, and in a relative sense the mechanisms of damage are not well understood, although they appear to have counterparts in radiation biochemistry. In view of the breadth of this topic, it is appropriate in the first section of this paper to direct attention to the major review sources in which information on the subject is summarized, and to some recently published papers. TABLE 1 lists some of the major factors in the suppression of lipid peroxidation. On the basis of the chemical properties of a-tocopherol and the mechanisms of antioxidation, a-tocopherol would be expected to react as a chain-breaking antioxidant in the inhibition of the free radical peroxidation of lipids. The propagation reaction in which the polyunsaturated lipid LH is peroxidized, L' + OZ'LOZ' LOZ. + LH+ LOOH + L' 1