Tannins and related compounds. XC. 8-C-ascorbyl (-)-epigallocatechin 3-O-gallate and novel dimeric flavan-3-ols, oolonghomobisflavans A and B, from oolong tea.(3).
作者:Fumio HASHIMOTO、Gen-ichiro NONAKA、Itsuo NISHIOKA
DOI:10.1248/cpb.37.3255
日期:——
A chemical examination of the polypenolic constituents in commercial oolong tea has led to the isolation of a new-flavan-3-ol, two novel dimeric flavan-3-ols named oolonghomobisflavans A and B eight new proanthocyanidins, together with twenty-one known polyphenols including proanthocyanidins, hydrolyzable tannins and red pigments. On the basis of chemical and spectroscopic evidence, the flavan-3-ol has been characterized as 8-C-ascorbyl (-)-epigallocatechin 3-O-gallate (22), while oolonghomobisflavans A (26) and B (27) have been determined to be dimeric flavan-3-ols in which two units are linked through a methylene bridge at the 8, 8'- and 8, 6'-positions, respectively. The structures of the new proanthocyanidins were elucidated mainly by tannase hydrolysis and thiolytic degradtion as epicatechin-(4β→8)-epigallocatechin 3-O-gallate (29), epicatechin 3-O-gallate-(4β→8)-epigallocatechin 3-O-gallate (30), catechin-(4α→8)-epigallocatechin 3-O-gallate (31), prodelphinidin B-4 3'-O-gallate (32), epicatechin 3-O-gallate-(4β→6)-epigallocatechin 3-O-gallate (33), epigallocatechin 3-O-gallate-(4β→6)-epicatechin 3-O-gallate (34), epiafzelechin 3-O-gallate-(4β→6)-epigallocatechin 3-O-gallate (35) and prodelphinidin B-2 3'-O-gallate (36).
对商业乌龙茶中的多酚成分进行化学检查,导致了一种新的黄烷-3-醇的分离,两个新型的二聚黄烷-3-醇被命名为乌龙双黄烷 A 和 B,以及八种新的原花青素,并与二十一种已知的多酚类物质包括原花青素、水解单宁和红色素一同发现。根据化学和光谱证据,该黄烷-3-醇被表征为8-C-抗坏血酸 (-)-表没食子酸-3-O-没食子酸酯(22),而乌龙双黄烷 A(26)和 B(27)被确定为二聚黄烷-3-醇,其中两个单元通过甲撑桥分别在8, 8'-和8, 6'-位连接。新的原花青素的结构主要通过单宁酶水解和硫解降解阐明,分别为表没食子酸-(4β→8)-表没食子酸-3-O-没食子酸酯(29)、表没食子酸-3-O-没食子酸酯-(4β→8)-表没食子酸-3-O-没食子酸酯(30)、儿茶素-(4α→8)-表没食子酸-3-O-没食子酸酯(31)、前南梅素 B-4 3'-O-没食子酸酯(32)、表没食子酸-3-O-没食子酸酯-(4β→6)-表没食子酸-3-O-没食子酸酯(33)、表没食子酸-3-O-没食子酸酯-(4β→6)-表没食子酸-3-O-没食子酸酯(34)、表阿伏塞黑素-3-O-没食子酸酯-(4β→6)-表没食子酸-3-O-没食子酸酯(35)和前南梅素 B-2 3'-O-没食子酸酯(36)。