Orejola Joanna, Matsuo Yosuke, Saito Yoshinori, Tanaka Takashi
Department of Natural Product Chemistry, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Molecules. 2017 Aug 6;22(8):1308. doi: 10.3390/molecules22081308.
, an important plant in Chinese traditional medicine, contains a complex mixture of proanthocyanidin oligomers as major constituents; however, only the minor components have been chemically characterized. In this study, oligomers with relatively large molecular weights, which form the main body of the proanthocyanidin fractions, were separated by adsorption and size-exclusion chromatography. Acid-catalyzed degradation in the presence of mercaptoethanol or phloroglucinol led to the isolation of 18 fragments, the structures of which were elucidated from their experimental and TDDFT-calculated ECD spectra. The results indicated that (-)-epigallocatechin was the main extension unit, while catechin, the A-type epigallocatechin-gallocatechin dimer, and the A-type epigallocatechin homodimer, were identified as the terminal units. Among the degradation products, thioethers of gallocatechin with 3,4- configurations, a B-type prodelphinidin dimer, a prodelphinidin trimer with both A- and B-type linkages, and a prodelphinidin dimer with an α-substituted A-type linkage were new compounds. In addition, a phloroglucinol adduct of an A-type prodelphinidin dimer, a doubly-linked phloroglucinol adduct of epigallocatechin, and a unique product with a flavan-3-ol skeleton generated by the rearrangement of the aromatic rings were also isolated.
作为中国传统医学中的一种重要植物，含有以原花青素低聚物为主要成分的复杂混合物；然而，只有少数成分得到了化学表征。在本研究中，通过吸附和尺寸排阻色谱法分离出了构成原花青素部分主体的相对大分子质量的低聚物。在巯基乙醇或间苯三酚存在下的酸催化降解导致分离出18个片段，其结构通过实验和TDDFT计算的ECD光谱得以阐明。结果表明，(-)-表没食子儿茶素是主要的延伸单元，而儿茶素、A-型表没食子儿茶素-没食子儿茶素二聚体和A-型表没食子儿茶素同二聚体被鉴定为末端单元。在降解产物中，具有3,4-构型的没食子儿茶素硫醚、一种B-型原花青定二聚体、一种同时具有A-型和B-型连接的原花青定三聚体以及一种具有α-取代A-型连接的原花青定二聚体是新化合物。此外，还分离出了一种A-型原花青定二聚体的间苯三酚加合物、表没食子儿茶素的双连接间苯三酚加合物以及一种由芳环重排产生的具有黄烷-3-醇骨架的独特产物。
