Matsuo Yosuke
Graduate School of Biomedical Sciences, Nagasaki University.
Yakugaku Zasshi. 2017;137(3):347-354. doi: 10.1248/yakushi.16-00207.
In recent years, plant polyphenols have attracted great attention due to their wide range of biological activities. Certain kinds of polyphenols have complex structures; therefore, it is difficult to elucidate their total structure, including stereochemistry. In this study, we reinvestigated the stereostructures of two major C-glycosidic ellagitannins contained in Quercus plants, vescalagin and castalagin, and revised their stereostructures based on theoretical calculations of spectroscopic data. We also determined the structures of quercusnins A and B, isolated from the sapwood of Quercus crispula, based on theoretical calculations of NMR data. The oxidation mechanism of polyphenols has not been entirely elucidated. Therefore, we have also studied the oxidation mechanism of tea catechins during black tea production. Our investigation of the oxidation mechanism of black tea pigment theaflavins revealed that the difference in the position of the galloyl ester affords different oxidation products of theaflavins. In addition, oxidation products of pyrogallol-type catechins could be classified into three types-dehydrotheasinensins, theacitrins, and proepitheaflagallins; their detailed production and degradation mechanisms were also examined.
近年来，植物多酚因其广泛的生物活性而备受关注。某些种类的多酚结构复杂；因此，很难阐明其包括立体化学在内的完整结构。在本研究中，我们重新研究了栎属植物中所含的两种主要碳苷鞣花单宁（vescalagin和castalagin）的立体结构，并基于光谱数据的理论计算修正了它们的立体结构。我们还基于核磁共振数据的理论计算确定了从日本槲栎边材中分离出的栎木素A和B的结构。多酚的氧化机制尚未完全阐明。因此，我们还研究了红茶生产过程中茶儿茶素的氧化机制。我们对红茶色素茶黄素氧化机制的研究表明，没食子酰酯位置的差异会产生不同的茶黄素氧化产物。此外，邻苯三酚型儿茶素的氧化产物可分为三种类型——脱氢茶黄素、茶橘红素和原表没食子儿茶素；还研究了它们详细的生成和降解机制。
