ELUCIDATION OF ANTIOXIDATIVE REACTION MECHANISM ON TREE PHENOLIC

为了开发木材提取物的有效利用，我们注意到木材酚类成分的抗氧化活性。本工作对黄酮醇的抗氧化能力进行了进一步的表征。首先，揭示了Gegan在黄酮醇的C3羟基上捕获自由基的反应途径。在主要实验前，以槲皮素-3-0-β-芦丁糖苷为原料制备了5，7，3‘，4’-四甲基槲皮素。以黄酮醇为代表的TMQ与两种具有较强和较弱反应活性的自由基引发剂反应。对分离出的反应产物分别进行了结构解析。此外，还得到了这些产品的时间历程。基于这两个结果，提出了两种漂白方式的可能反应途径。其次，以查尔酮、极光酮、异黄酮、黄烷-3-醇等天然黄酮类化合物和黄酮类化合物为引发剂，对常用的分光光度法和停流法捕获1，1-二苯基-2-苦皮酰肼(DPPH)的能力进行了对比实验。从这些结果可以看出，黄酮醇具有更大的优势。此外，由于自由基捕获的反应速度不同，抗氧化性成分可能分为两类。

We noticed on the antioxidative activity of wood phenolic constituents in order to develop the effective utilization of the extractives. On the present work, further characterization of flavonols on the antioxidative ability was undertaken.At first, the revealing of radical-capturing reaction pathway which gegan at the C3 hydroxyl group of the flavonol was aimed. Before the main experiment, 5,7,3',4'-tetramethylquercetin (TMQ) was prepared from quercetin-3-0-β-rutinoside. TMQ representing flavonols was reacted with two radical initiators having strong and weak reactivities. The structures of isolated reaction products were elucidated, respectively. Also, the time course of these products were obtained. Based on both results, a possible reaction pathway having two blanched ways was presented. It was revealed that the reaction behavior of two subways was different between two radical initiators.Nextly, comparison experiments of the radical-capturing ability against 1,1-diphenyl-2-picrylhydrazil (DPPH) by usual spectroscophic and stopped flow methods were carried out, using natural flavonoids such as chalcone, aurone, isoflavone, flavan-3-ols, and other compounds, together with flavonol constituents. From these results, the more advantage of flavonols was indicated. Furthermore, it was revealed that antioxidative constituents might be divided into two groups due to the reaction speed of radical-capturing.