黄芪多糖的分离、结构表征及益生活性研究

Isolation,structure characterization and prebiotic activity of polysaccharides from Astragalus membranaceus

对从蒙古黄芪中分离纯化获得的APS-1和APS-2进行结构表征,同时考察黄芪粗多糖(Astragalus crude polysaccharide,APS)的益生活性。运用高效凝胶过滤色谱(high performance size exclusion chromatography,HPGFC)、离子色谱(ion chromatography,IC)、红外(infrared spectroscopy,FT-IR)和核磁(nuclear magnetic resonance spectros copy,1H-NMR)技术分析APS-1和APS-2的分子质量、单糖组成和糖苷键类型。利用人体粪便体外发酵APS,通过气相色谱法分析短链脂肪酸(short-chain fatty acids,SCFA)的产生来评价APS的益生活性。结果显示,APS-1和APS-2分子质量分别为38.4和5.2 k Da。APS-1主要由半乳糖和葡萄糖组成,摩尔比为1∶49.76。APS-2主要由鼠李糖、半乳糖和葡萄糖组成,摩尔比为1∶2.99∶16.26。APS-1以α-糖苷键为主,APS-2同时包含α-糖苷键和β-糖苷键。当APS的添加量为5 g/L时,发酵培养基的p H从7.49(0 h)降至5.88(48 h),总SCFA、乙酸、丙酸和丁酸的含量均显著增加。结果表明,APS被肠道微生物代谢后可以产生对人体具有良好益生活性的短链脂肪酸。

A water-soluble crude polysaccharide named as APS was isolated from the roots of Mongolia Astragalus membranaceus by hot water extraction and its in vitro prebiotic activity was tested.After purification,two main polysaccharides(APS-1 and APS-2)with relative molecular masses of 38.4 kDa and 5.2 kDa were collected.Their structural characteristics were investigated by high performance gel filtration chromatography(HPGFC),ion chromatography(IC),fourier transform infrared spectroscopy(FTIR)and nuclear magnetic resonance spectroscopy(1 H-NMR).Based on the data obtained,APS-1 was mainly composed of galactose and glucose with a molar ratio of 1∶49.76.APS-2 was mainly composed of rhamnose,galactose and glucose with a molar ratio of 1∶2.99∶16.26.APS-1 was found to be mainly composed ofα-type glycosidic bonds while APS-2 contained bothα-type glycosidic bonds andβ-type glycosidic bonds.When APS(5 g/L)was fermented by human feces,the pH of the medium decreased from 7.49(0 h)to 5.88(48 h),and the contents of total short-chain fatty acids(SCFA),acetic acid,propionic acid,and butyric acid were all significantly increased.The results showed that APS had great prebiotic activity to human intestinal microbes.