Physiological functions of vitamin E and biodiscrimination of its stereoisomers.
Vitamin E is recognized as a fat-soluble antioxidant able to scavenge oxygen radicals and to quench singlet oxygen. Of 8 analogues of vitamin E alpha-tocopherol has the highest biological activity. In addition, all-rac-alpha-tocopherol 2R-stereoisomers are more active than their 2S-counterparts. To cast light on the significance of this in vivo, we investigated the discrimination and distribution of alpha-tocopherol stereoisomers in rats using chiral-HPLC. Alpha-tocopherol was found to be absorbed from the small intestine without discrimination. After transfer to the liver, however, 2R-isomers are preferentially secreted into VLDL. In this discrimination the alpha-tocopherol transfer protein functions as a key substance.
Igarashi
O
O
Institute of Environmental Science for Human Life, Ochanomizu University, Japan.
Kiyose
C
C
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D006801:Humans; D051381:Rats; D013237:Stereoisomerism; D014810:Vitamin E / Q000378:metabolism*
D000975:Antioxidants; D014810:Vitamin E