羊栖菜岩藻聚糖硫酸酯的结构研究

【作者】 徐杰；

【导师】 李八方； 薛长湖；

【作者基本信息】 中国海洋大学 ， 水产品加工与贮藏工程， 2003， 硕士

【摘要】 岩藻聚糖硫酸酯是一种具有独特结构和多种生物活性的多糖，其构效关系是近些年来的研究热点。本文从浙江省洞头县海域养殖羊栖菜中提取岩藻聚糖硫酸酯，利用Q-Sepharose FF阴离子交换树脂分级，得到硫酸基含量不同的三个组分：F-1，F-2和F-3，经化学组成分析和分子量测定，发现组分F-2不但得率较高而且组成较单一，主要单糖组成为岩藻糖和半乳糖，硫酸基含量高且糖醛酸含量低，因此对组分F-2进行进一步的结构分析，主要使用了高效凝胶过滤色谱、高效薄层色谱、红外光谱、酸水解、甲基化反应、气—质联用色谱和核磁共振光谱等方法， HPSEC法测定表明组分F-2的分子量在160,000左右。IR分析发现F-2中存在双硫酸基取代的情况。用GC-MS对F-2和其脱硫产物F-2d的甲基化产物进行分析和比较，由此提出F-2中岩藻糖是以1→3连接为主，半乳糖是以1→6连接为主，硫酸基主要取代在岩藻糖残基的C-4位上，其次在C-2位，还有C-2,4位双硫酸基取代。 组分F-2的酸水解产物利用截留分子量为5,000(Da)的超滤膜分离后通过Bio-Gel P4凝胶柱分为F-2-a，F-2-b和F-2-c三个寡糖组分。通过将这些组分的化学组成及分子量与F-2作比较，认为F-2是含有大量岩藻糖和半乳糖支链的杂多糖，其主链主要由岩藻糖、半乳糖、甘露糖和葡萄糖构成，且主链和支链均有硫酸基取代。 利用核磁共振波谱法对F-2水解得到的寡糖组分F-2-c进行结构分析，结合甲基化的结果，证明了F-2支链结构主要是由1→3连接的岩藻糖残基构成的，还有少量的1→2连接；岩藻糖残基主要为α构型，也有少量的β构型；支链中半乳糖残基与主链不同是1→3连接，为β构型。更多还原

【Abstract】 Fucoidan, a mixture of sulfated fucose-containing polysacchrides, have unique molecular structure and many biological activities. Now the structure-activity relationship of fucoidan is widely studied. Fucoidan were extracted from brown seaweed Sargassum fusiforme, and the alga was cultured in the coast of Dongtou of ZheJiang province. Fucoidan was separated by anion-exchange chromatography on Q-Sepharose FF into three fractions (F-l, F-2 and F-3). The second fraction which named as F-2 was more homogeneous and abounded in both fucose residues and sulfated esters. We chose F-2 for the further structural studies to the analysis of their chemical compositions and average molecular weight. Analysis methods of HPSEC, GC, TLC, IR, acid hydrolysis, methylation reaction (GC-MS) and NMR were used to elucidate its structure.The average molecular weight of F-2 was estimated at 160,000, based on HPSEC. The IR spectrum displayed that disulfated fucose existed in F-2. F-2 and its desulfated derivative F-2d were subjected to methylation analysis by GC-MS. It showed that a (1 - 3)-linkage was major linkage pattern in fucose residues and (1-6)-linkage was major linkage pattern in galactose residues. Sulfate groups were substituted mainly at C-4 positions and C-2 of fucose residues, some of fucose residues were disulfated at C-2,4 positions.After hydrolyzation with TFA of F-2 and ultrafiltration (MWCO 5000), the mixture was applied to Bio-gel P4 column, three hydrolytic products were obtained (F-2-a, F-2-b and F-2-c). By comparing their chemical compositions and average molecular weight with F-2, we deduce that main chains of F-2 composed of fucose, galactose, mannose and glucose, and a considerable amount of galactofucan side chains (F-2-c) with about 6-8 sugar units. Sulfation occurs on both main and side chains.The NMR analysis of oligosaccharide F-2-c was consistent with the methylation analysis, including the mainly linkage pattern and substituted positions. We found F-2-c mainly formed by (l-3)-linked a-fucose residues (sulfated at C-4 or C-2,4 positions), and also found some fucose residues with configuration, but (1 -3)-linkage was major linkage pattern of p-galactose residues in the side chains of F-2.更多还原