姬松茸多醣之化學結構與生物活性分析

Abstract

食用蘑菇富有營養價值。近年來，食用蘑菇多醣的生物活性引發了越來越多的關注。因此，爲了理解結構與活性（SAR），就必須瞭解多醣體的化學結構。在本篇研究中，選用了常被食用的的姬松茸進行研究。通過冷水萃取姬松茸中多醣，接著通過冷丙酮將多醣沉澱，分子篩層析法和離子交換樹脂法進行多醣的分離與純化。生物活性的部分則針對多醣對免疫刺激活性以及α-葡萄糖苷酶的抑制能力進行研究。純化後的多醣體則通過氣相層析質譜儀（GC-MS）和核磁共振（NMR）光譜進行解析。 實驗結果表明ASP-1具有α-葡萄糖苷酶抑制活性，在濃度為2.5 mg/mL時，抑制能力達58%。通過氣相層析質（GC-MS）和核磁共振（NMR）光譜分析，證明姬松茸多醣（ASP-1）主要由66%的半乳糖，以及15%的岩藻糖、10%的葡萄糖和9%的甘露糖所組成。藉由醣鍵結分析姬松茸多醣（ASP-1）的骨架是由1,4-連接的葡萄糖基、1,2-連接的半乳糖基、1,6-連接的半乳糖基、1,2,6-連接的半乳糖基以及具末端鍵結的岩藻糖、葡萄糖和甘露糖組成。 本研究表明姬松茸多醣（ASP-1）具有抑制α-葡萄糖苷酶的活性，希望在不久的將來姬松茸多醣（ASP-1）可以用作為食品添加劑或是食品補充劑用來治療第二型糖尿病。

Edible mushrooms are a good source of valuable nutritious ingredients. Recently, mushroom polysaccharides attract increasing attentions on their biological activities. Therefore, elucidation of their chemical structures is imperative for understanding structure-activity relationship (SAR). In the present study, a popular mushroom species, Agaricus blazei Murrill (姬松茸), was selected for studying. The polysaccharide of Agaricus blazei Murrill was extracted by cold water first and precipitated by cold-acetone, and sequentially purified by size exclusion and ion exchange chromatographies. Biological activities of polysaccharides were investigated to study immunological activity and α-d-glucosidase inhibitory activity. Chemical structure of purified polysaccharide was analyzed by gas chromatography-mass spectroscopy (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Experimental results revealed that water-soluble polysaccharide ASP-1 had some inhibitory activity on α-glucosidase in a dose-dependent manner, with the inhibitory rate of 58% when the concentration reached 2.5 mg/mL. The chemical structure of ASP-1 was analyzed by gas chromatography-mass spectroscopy and NMR spectra. The results demonstrated that the polysaccharide of Agaricus blazei Murrill (ASP-1; MW~70 kDa) was composed of galactose (66%), fucose (15%), glucose (10%) and mannose (9%). According to the combination of chemical and instrumental analysis, the results indicated that ASP-1 had a backbone consisting of (1 → 4)-linked-α-D-glucopyranosyl, (1 → 2)-linked-α-D- galactopyranosyl, (1 → 6)-linked-α-D-galactopyranosyl and (1 → 2, 6)-linked-α-D-glucopyranosyl linkage, and terminal mannosyl, fucosyl and galactosyl linkage, respectively. The present study indicated that ASP-1 has inhibitory activity of α-glucosidase, which may have potential as a food additive or as a food supplement for an enzyme-targeted treatment of Type 2 diabetes in the near future.