An α-1, 6-linked galactomannan was isolated and purified from natural Cordyceps sinensis. The fine structure analysis of this polysaccharide was elucidated based on partial acid hydrolysis, monosaccharide composition, methylation and 1D/2D nuclear magnetic resonance (NMR) spectroscopy. Monosaccharide composition analysis revealed that this polysaccharide was mainly composed of galactose (68.65%), glucose (6.65%) and mannose (24.02%). However, after partial acid hydrolysis the percentages of galactose, glucose and mannose were changed to 3.96%, 13.82% and 82.22%, respectively. The molecular weight of this polysaccharide was 7207. Methylation and NMR analysis revealed that this galactomannan had a highly branched structure, mainly consisted of a mannan skeleton and galactofuranosyl chains. The structure of galactofuranosyl part was formed by alternating (1 → 5)-lined β-Galf and (1 → 6)-liked β-Galf or a single (1 → 6)-liked β-Galf, attaching to the O-2 and O-4 of the mannose chain, and terminated at β-T-Galf. The mannan core was revealed by analyzing the partial acid hydrolysate of the galactomannan and the structure was composed of (1 → 6)-linked α-Manp backbone, with substituted at C-2 by short chains of 2-substituted Manp or Galf branches.

中文翻译：

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来自天然冬虫夏草的 α-1、6 联半乳甘露聚糖的结构表征

从天然冬虫夏草中分离纯化出一种 α-1、6 联半乳甘露聚糖。该多糖的精细结构分析基于部分酸水解、单糖组成、甲基化和一维/二维核磁共振 (NMR) 光谱进行阐明。单糖组成分析表明，该多糖主要由半乳糖（68.65%）、葡萄糖（6.65%）和甘露糖（24.02%）组成。然而，在部分酸水解后，半乳糖、葡萄糖和甘露糖的百分比分别变为3.96%、13.82%和82.22%。该多糖的分子量为7207。甲基化和核磁共振分析表明，该半乳甘露聚糖具有高度支化的结构，主要由甘露聚糖骨架和呋喃半乳糖链组成。呋喃半乳糖部分的结构是由交替的 (1 → 5)-lined β-Galf 和 (1 → 6)-like β-Galf 或单个 (1 → 6)-like β-Galf 连接到 O-2和甘露糖链的 O-4，终止于 β-T-Galf。通过分析半乳甘露聚糖的部分酸水解产物揭示了甘露聚糖核心，其结构由 (1 → 6) 连接的 α-Manp 主链组成，在 C-2 处被 2-取代的 Manp 或 Galf 分支的短链取代。