Study on physiological role of new vitamin E

从大麻哈鱼卵中分离出一种新的维生素E组分，α-生育酚（α-Toc）的类异戊二烯链末端有一个不寻常的亚甲基不饱和键，它在37℃下的甲醇或脂质体悬浮液中具有与α-Toc相同的抗氧化活性。在这里，我们报告说，这种海洋来源的生育酚（MDT）广泛分布在海洋鱼类的组织中，总维生素E的MDT组成在冷水鲑鱼肉（12-20%）比热带鱼（[小于或等于] 2.5%）。维生素E分析养殖的马苏三文鱼保持MDT耗尽的饮食显示，MDT含量大大低于本地马苏三文鱼，这表明MDT的营养来源。这一论点得到了北海道寒冷沃茨中海洋浮游生物中MDT发现的支持。我们发现MDT在0℃时比α-Toc更能抑制脂质体的过氧化反应。在0℃时，MDT和α-Toc与过氧化氢自由基的速率常数比值随脂质体和鱼油中自由基通量的减小而增大，表明MDT在低温下的活性增强是由于其在粘性脂质中的扩散速率增大。这些结果表明，MDT生产，或其营养积累，可能会减少脂质过氧化作用的海洋生物功能适应冷水环境。

A new vitamin E constituent having an unusual methylene unsaturation at the isoprenoid-chain terminus of α-tocopherol (α-Toc) was isolated from chum salmon eggs and was found to have identical antioxidant activity as does α-Toc in methanol or liposomal suspension at 37℃. Here we report that this marine-derived tocopherol (MDT) is broadly distributed with α-Toc in the tissue of marine fish, and that the MDT composition of total vitamin E is greater in the flesh of coldwater salmon (12-20%) than in that of tropical fish (【less than or equal】 2.5%). Vitamin E analysis of cultured masu salmon maintained on a MDT-deplete diet showed substantially less MDT content than native masu salmon, suggesting a trophic origin of MDT. This contention is supported by the finding of MDT in marine plankton from the cold waters of Hokkaido. We found that MDT inhibited peroxidation of cholesterol-containing phosphatidylcholine liposomes to a greater extent than did α-Toc at 0℃. Furthermore, the ratios of the rate constants for MDT and α-Toc to scavenge peroxyl radicals increased with decreasing rates of radical flux in liposomes and fish oil at 0℃, indicating that the enhanced activity of MDT at low temperature is attributed to its greater rate of diffusion in viscous lipids. These results suggest that MDT production, or its trophic accumulation, may reduce lipid peroxidation in marine organisms functionally adapted to coldwater environments.