Pharmacokinetics of α-tocopherol stereoisomers in plasma and milk of cows following a single dose injection of all-rac-α-tocopheryl acetate.

ABSTRACT

Among different stereoisomers of all-rac-α-tocopherol, 2R-stereoisomers have higher biological activities than their 2S-stereoisomers. Two experiments were conducted to study the pharmacokinetics of stereoisomers of all-rac-α-tocopherol and investigated the discrimination and distribution of α-tocopherol stereoisomers in plasma and milk as well as quantitative secretion into milk with lactating Holstein cows after a single dose intramuscular injection of 2.50 g of all-rac-α-tocopheryl acetate. The highest half-life (2.92/h) and lowest elimination rate (0.36/h) were found for RRR-α-tocopherol. After a single dose injection of all-rac-α-tocopherol, highest maximal daily increase (Smax, 8.36 mg/day) and accumulation secretion (AS, 50.8 mg) were observed for milk RRR-α-tocopherol. The majority of the Æ©2S stereoisomers were found in the liver 36 h post injection, while the 2R stereoisomers were more equal distributed between liver and plasma. The present findings showed a clear discrimination between RRR-α-tocopherol, synthetic 2R stereoisomers and Æ©2S stereoisomers in milk and plasma of dairy cows.