Department of Chemistry, Wuhan University, Wuhan 430072, China.
J Agric Food Chem. 2012 Apr 4;60(13):3498-506. doi: 10.1021/jf300423z. Epub 2012 Mar 22.
A water-soluble neutral polysaccharide (AF1) was extracted from Auricularia (A.) auricula-judae with 0.15 M aqueous NaCl at 80-100 °C. Its chemical components and structure were analyzed by GC, GC-MS, and NMR. AF1 was identified as a β-(1→3)-D-glucan with two β-(1→6)-D-glucosyl residues for every three main chain glucose residues, showing a comb-branched structure. The M(w) values of AF1 in both aqueous solution and DMSO determined by LLS and SEC-LLS were in the narrow range of 2.07-2.15 × 10(6), indicating AF1 existed as single chains in the two solvents. The high intrinsic viscosity [η] of 1753 mL/g and the structure-sensitive parameter ρ (≡R(g)/R(h)) value of 2.3 in water revealed that AF1 existed as stiff chain conformation. Moreover, we directly observed the extended stiff chain conformation by AFM. The branching structure led to the water solubility of AF1, and the intramolecular hydrogen bonds sustained the stiff chain conformation. The rheological results showed that this polysaccharide aqueous solution had higher viscosity than even xanthan, a pronounced thickening agent. This work provided important information for developing new thickeners in food fields, and how neutral polysaccharides can be used as good candidates.
一种水溶性中性多糖（AF1）从银耳（A.）耳状中用 0.15 M 盐水在 80-100°C 下提取。通过 GC、GC-MS 和 NMR 分析其化学成分和结构。AF1 被鉴定为β-(1→3)-D-葡聚糖，每三个主链葡萄糖残基有两个β-(1→6)-D-葡萄糖基残基，呈梳状分支结构。通过 LLS 和 SEC-LLS 在水溶液和 DMSO 中测定的 AF1 的 M(w) 值在 2.07-2.15×10(6)的窄范围内，表明 AF1 在两种溶剂中均以单链形式存在。高特性粘度[η]为 1753 mL/g，结构敏感参数ρ（≡R(g)/R(h))值为 2.3，表明 AF1 呈刚性链构象。此外，我们通过 AFM 直接观察到伸展的刚性链构象。分支结构导致了 AF1 的水溶性，而分子内氢键维持了刚性链构象。流变学结果表明，这种多糖水溶液的粘度甚至高于 xanthan，一种明显的增稠剂。这项工作为开发食品领域的新型增稠剂提供了重要信息，以及中性多糖如何可以作为良好的候选物。
