Duan Jinyou, Zheng Yun, Dong Qun, Fang Jinian
Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, People's Republic of China, 201203.
Phytochemistry. 2004 Mar;65(5):609-15. doi: 10.1016/j.phytochem.2003.12.002.
A pectic polysaccharide DL-2A with a molar mass of 8.5 x 10(5), was obtained from the boiling water extract of Diospyros kaki leaves. It had [alpha]20D -21.8 degrees (c 0.22, H2O) and consisted of rhamnose, arabinose, galactose, xylose and galacturonic acid units in the molar ratio of 0.4:3.4:2.4:1.0:0.8, along with traces of glucuronic acid. About 16.7% of galacturonic acid existed as the methyl ester. A combination of linkage analyses, periodate oxidation, partial acid hydrolysis, selective lithium-degraded reaction, ESIMS, 1H- and 13C- NMR spectral analyses revealed its structural features. It was found that DL-2A possessed an alpha-(1-->4)-galacturonan backbone with some insertions of alpha-1,2-Rhap residues. The side-chains of arabino-3,6-galactan were attached to the backbone via O-4 of Rhap residues and O-3 of GalAp residues, while 4-linked xylose residues (forming short linear chains) were directly linked to O-4 of rhamnose residues, not as part of the xylogalacturonan. These novel structural features enlarge the knowledge on the fine structure of pectic substances in the plant kingdom.
从柿叶的沸水提取物中获得了一种摩尔质量为8.5×10⁵的果胶多糖DL-2A。其比旋光度[α]₂₀ᴅ为 -21.8°（c 0.22，H₂O），由鼠李糖、阿拉伯糖、半乳糖、木糖和半乳糖醛酸单元组成，摩尔比为0.4:3.4:2.4:1.0:0.8，还含有痕量的葡萄糖醛酸。约16.7%的半乳糖醛酸以甲酯形式存在。通过结合键合分析、高碘酸盐氧化、部分酸水解、选择性锂降解反应、电喷雾电离质谱（ESIMS）、¹H-和¹³C-核磁共振光谱分析揭示了其结构特征。发现DL-2A具有α-(1→4)-半乳糖醛酸聚糖主链，并插入了一些α-1,2-鼠李糖残基。阿拉伯-3,6-半乳聚糖的侧链通过鼠李糖残基的O-4和半乳糖醛酸残基的O-3连接到主链上，而4-连接的木糖残基（形成短线性链）直接连接到鼠李糖残基的O-4上，并非作为木糖基半乳糖醛酸聚糖的一部分。这些新的结构特征扩展了对植物界果胶物质精细结构的认识。
