Preparation and Characterization of 8a-(Phosphatidylcholine-dioxy)- α-tocopherones and their Formation during the Peroxidation of Phosphatidylcholine in Liposomes
作者:Ryo YAMAUCHI、Hiromi MIZUNO、Koji KATO
DOI:10.1271/bbb.62.1293
日期:1998.1
α-Tocopherol was reacted with the phosphatidylcholines (PCs), 1-palmitoyl-2-linoleoyl-3-sn-PC (PLPC), 1-palmitoyl-2-linolenoyl-3-sn-PC, 1-palmitoyl-2-arachidonoyl-3-sn-PC (PAPC) and 1-stearoyl-2-arachidonoyl-3-sn-PC, in the presence of the free radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile), at 37°C. The addition products of α-tocopherol with the PC peroxyl radicals were isolated and identified as 8a-(PC-dioxy)-α-tocopherones, in which the peroxyl radicals derived from each PC molecule attacked the 8a-position of the α-tocopheroxyl radical. The antioxidative efficiency of α-tocopherol against the peroxidation of PLPC and PAPC in liposomes was assessed by the formation of the reaction products of α-tocopherol. When α-tocopherol was oxidized in the presence of the water-soluble free radical initiator, 2,2′-azobis(2-amidinopropane) dihydrochloride, epoxy-α-tocopherylquinones were mainly produced together with 8a-(PC-dioxy)-α-tocopherones and α-tocopherylquinone. The yield of α-tocopherylquinone was increased by treating each sample with dilute acid which indicates the presence of tocopherone precursors other than the 8a-(PC-dioxy)-α-tocopherones. The same products were also detected from iron-dependent peroxidation, although the yields were very low.
在自由基存在的情况下,α-生育酚与磷脂酰胆碱(PC)、1-棕榈酰-2-亚油酰-3-sn-PC(PLPC)、1-棕榈酰-2-亚麻酸酰-3-sn-PC(PAPC)和 1-硬脂酰-2-丙烯酰-3-sn-PC(PLPC)发生反应、在自由基引发剂 2,2′-偶氮双(2,4-二甲基戊腈)的作用下,于 37°C 加入 1-棕榈酰-2-丙烯酰-3-sn-PC(PAPC)和 1-硬脂酰-2-丙烯酰-3-sn-PC。经分离鉴定,α-生育酚与 PC 过氧化自由基的加成产物为 8a-(PC-二氧)-α-生育酚酮,其中每个 PC 分子产生的过氧自由基攻击α-生育酚自由基的 8a 位。通过α-生育酚反应产物的形成,评估了α-生育酚对脂质体中PLPC和PAPC过氧化反应的抗氧化效率。当α-生育酚在水溶性自由基引发剂2,2′-偶氮双(2-脒基丙烷)二盐酸盐存在下被氧化时,主要生成环氧-α-生育酚醌和8a-(PC-二氧)-α-生育酚酮以及α-生育酚醌。用稀酸处理每个样品后,α-生育醌的产量都有所增加,这表明除了 8a-(PC-二氧)-α-生育酚酮外,还存在生育酚酮前体。在铁依赖性过氧化反应中也检测到了相同的产物,不过产量很低。