Biodiscrimination of alpha-tocopherol stereoisomers in plasma and tissues of lambs fed different proportions of all-rac-alpha-tocopheryl acetate and RRR-alpha-tocopheryl acetate

摘要

A ratio of 1.36:1 in relative bioactivity of RRR-alpha-tocopheryl acetate as a natural (Nat-alpha-T) source to all-rac-alpha-tocopheryl-acetate, as a synthetic (Syn-alpha-T) source, is generally accepted. This factor also largely reflects the difference in bioavailability. However, studies indicate that neither bioavailability of alpha-tocopherol stereoisomers nor relative bioavailability between them are constant, but are dose-dependent and differ between organs. However, no information is available about how different ratios between synthetic and natural alpha-tocopherol affect bioavailability of alpha-tocopherol stereoisomers. Thirty lambs were randomly assigned to diets supplied with additives containing 5 different Syn-alpha-T to Nat-alpha-T ratios, including 100: 0, 75: 25, 50: 50, 25: 75, and 0:100. The experiment lasted for 70 d after which the lambs were slaughtered. The amount of RRR-alpha-tocopherol generally increased in plasma and organs with increasing the proportion of Nat-alpha-T in the diet (P & 0.05). However, the relative bioavailability of RRR- and RRS-alpha-tocopherol in plasma, organs, and abdominal fat generally decreased with increasing the proportion of Nat-alpha-T in the diet (P & 0.05), whereas the other stereoisomers only showed minor changes with the exception of liver. However, a linear response was maintained between the ratio of stereoisomers in the feed and the ratio in plasma and organs. In conclusion, regardless of Syn-alpha-T to Nat-alpha-T ratio in the diets, amounts of alpha-tocopherol stereoisomers in plasma, brain, heart, lungs, and abdominal fat were in the following order: RRR & RRS, RSR, RSS & Sigma 2S.