Physiological functions of vitamin E and biodiscrimination of its stereoisomers

Vitamin E is recognized as a fat-soluble anti-oxidant able to scavenge oxyg en radicals and to quench singlet oxygen. Of 8 analogues of vitamin E alpha -tocopherol has rite highest biological activity. In addition, all-rac-alph a-tocopherol 2R-stereoisomers are more active than their 2S-counterparts. T o cast light on the significance of this in vivo, we investigated the discr imination and distribution of alpha-tocopherol stereoisomers in rats using chiral-HPLC. Alpha-tocopherol was found to be absorbed from the small intes tine without discrimination. After transfer to the liver; however; 2R-isome rs are preferentially secreted into VLDL. In this discrimination the alpha- tocopherol transfer protein functions as a key substance.