Chemical Studies on Antioxidative Activities of Tree Phenolic Extractives and Their Functions for Higher Utilization.

近年来，木材提取物的各种生物活性被认为是提高和有效利用树木资源的重要途径。然后，我们对木材酚类成分的抗氧化活性进行了研究。已对80多种成分进行了测试，发现了许多具有高抗氧化活性的成分。此外，还探讨了抗氧化活性的产生与效力和化学结构的关系。本研究的目的是对天然黄酮类化合物的活性再次进行精确的比较，并解释黄酮类化合物与酚类化合物的反应机理，因为目前还没有揭示黄酮类化合物与酚类化合物的反应机理。首先，用止流法可以明确不同位置有多个羟基的黄酮类化合物对1,1-二苯基-2-苦味水杨酸（DPPH）自由基的捕获能力的细微差异。即以具体的自由基捕获常数给出了环周醇、槲皮素和杉木素的抗氧化活性。然后，以槲皮素及其糖苷（芦丁）为原料制备各种槲皮素甲基衍生物，揭示槲皮素的抗氧化反应机理。在主实验前，按上述方法确定了它们的自由基捕获常数。以3-羟基黄酮和3-甲氧基黄酮为底物，与2,2'-偶氮-（2,4-二甲基戊腈）（AMVN）进行了体外反应。然后，得到反应产物和/或检测。采用高效液相色谱法测定产物随时间的变化。据此，通过一系列实验，提出了3-羟基黄酮（黄酮醇）的抗氧化反应。

Recently, various bioactivities of wood extractives are noted for higher and effective uses of tree resources. Then, we are studiing on the antioxidative activity of wood phenolic constituents. Over 80 constituents had been tested already, and many constituents with high antioxidative activity had been found out. Also, the relationship to potency and chemical structure on the generation of antioxidative activity.On the present study, the objects were to compare precisely the activity of natural flavonoids again, and to explain the reaction mechanism of flavonoid, because the mechanism with phenolic compounds had not been revealed so far.At first, the fine difference of radical capturing abilities among flavonnoids with plural hydroxyl groups at same positions, on 1,1-diphenyl-2-picrylhydragil (DPPH) radical could be clarifed by the stopped flow method. Namely, antioxidative activities for eriodictiol, quercetin and taxifolin were given in concrete radical capturing constants. Nextly, various methyl derivatives of quercetin were prepared from quercetin and its glycoside (rutin) for revealing experiment of antioxidative reacttion mechanism. Before main experiment, their radical capturing constants were determined as mentioned above. While using 3-hydroxyflavone and 3-methoxyflavone as substrate, the reaction with 2,2'-azobis-(2,4-dimethylvarelonitrile) (AMVN) in vitro was undertaken. Then, the reaction products were obtained and/or detected. Furthemore, the change of products with time were determined by HPLC.Accordingly, as a results of a series of experiments, the antioxidative reaction 3-hydroxyflavone (flavonol) can been proposed.