1(Key Laboratory of Carbohydrate Chemistry and Biotechnology(Jiangnan University), Ministry of Education, Wuxi 214122,China); 2(School of Biotechnology, Jiangnan University, Wuxi 214122, China); 3(Department of Radiology,Wuxi Second Hospital Affiliated to Nanjing Medical University,Wuxi 214002,China)
Abstract: 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(1H-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 of α-type glycosidic bonds while APS-2 contained both α-type glycosidic bonds and β-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.
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