Biodiscrimination of alpha-tocopherol stereoisomers during intestinal absorption.
Synthetic alpha-tocopherol (alpha-Toc) contains equal amounts of eight different stereoisomers, and the four stereoisomers with the 2R configuration are generally more active than their corresponding 2S-isomers. We investigated the biodiscrimination of alpha-Toc stereoisomers during intestinal absorption in situ and in vitro. Intestinal absorption of alpha-Toc stereoisomers was examined in situ in vitamin E-deficient rats with cannulated thoracic ducts. We found that the ratios of alpha-Toc stereoisomers in lymph of the all-rac-alpha-Toc group were the same as the administered alpha-Toc stereoisomers, and 2R-isomers occupied approximately 50% of absorbed alpha-Toc. The uptake of alpha-Toc stereoisomers also was measured using Caco-2 cells cultured on filter membranes. The concentration of RRR-alpha-Toc in Caco-2 cells was not significantly different from that of SRR-alpha-Toc. Therefore, the discrimination of alpha-Toc stereoisomers does not occur during absorption in small intestine, suggesting the liver as source for the biodiscrimination.
Kiyose
C
C
Institute of Environmental Science for Human Life, Ochanomizu University, Tokyo, Japan.
Muramatsu
R
R
Fujiyama-Fujiwara
Y
Y
Ueda
T
T
Igarashi
O
O
D000818:Animals; D007408:Intestinal Absorption; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014810:Vitamin E / Q000737:chemistry* / Q000378:metabolism*; D014811:Vitamin E Deficiency / Q000378:metabolism
D014810:Vitamin E