Synthesis of Lipophilic Poly-Lauroyl-(+)-Catechins and Radical-Scavenging Activity
作者:Guangzhi JIN、Hisashi YOSHIOKA
DOI:10.1271/bbb.69.440
日期:2005.1
Lipophilic catechins were synthesized to improve absorption into living bodies and obtain new antioxidants effective in lipid bilayers. The hydroxyl (OH) groups of (+)-catechin was acylated randomly using lauroyl chloride. The mixture was separated by preparative HPLC, and 3-lauroyl-, 3′,4′-dilauroyl- and 3,3′,4′-trilauroyl-catechins (3-LC, 3′,4′-LC, and 3,3′,4′-LC) were obtained, their structures being determined by 1H NMR. Their radical scavenging activity was measured in a ethanol solution using the 1,1-diphenyl-2-picrylhydrazyl radical, and was compared with that of (+)-catechin. The activity of 3-LC was almost same as that of (+)-catechin, but those of 3′,4′-LC and 3,3′,4′-LC were small, showing that the blocking of phenolic OH groups in the B ring lowered the activity. The scavenging activity on lipophilic radicals in a liposome system was also measured, and the activities were in the order of 3-LC > 3′,4′-LC = (+)-catechin. These results suggested that radical scavenging activity in the lipid membrane depended not only on the number and the relative positions of phenolic OH groups of catechins but also on affinity to the membrane.
合成亲脂性儿茶素的目的是提高活体吸收率,并获得在脂质双分子层中有效的新型抗氧化剂。用月桂酰氯随机酰化(+)-儿茶素的羟基(OH)。混合物经制备型高效液相色谱分离,得到 3-月桂酰基、3′,4′-二月桂酰基和 3,3′,4′-三月桂酰基儿茶素(3-LC、3′,4′-LC 和 3,3′,4′-LC),并通过 1H NMR 确定了它们的结构。在乙醇溶液中用 1,1-二苯基-2-苦基肼自由基测定了它们的自由基清除活性,并与(+)-儿茶素的自由基清除活性进行了比较。3-LC的活性与(+)-儿茶素基本相同,但3′,4′-LC和3,3′,4′-LC的活性较小,这表明B环中的酚羟基受阻降低了活性。此外,还测定了脂质体系统中的亲脂自由基清除活性,其顺序为 3-LC > 3′,4′-LC=(+)-儿茶素。这些结果表明,儿茶素在脂膜中的自由基清除活性不仅取决于酚羟基的数量和相对位置,还取决于与膜的亲和性。