Chinese Journal of Chromatography ›› 2014, Vol. 32 ›› Issue (12): 1306-1312.DOI: 10.3724/SP.J.1123.2014.08023

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Structural characterization of Astragalus polysaccharides using partial acid hydrolysis-hydrophilic interaction liquid chromatography-mass spectrometry

LIANG Tu1, FU Qing1, XIN Huaxia1, LI Fangbing1, JIN Yu1, LIANG Xinmiao1,2   

  1. 1. School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China;
    2. Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
  • Received:2014-08-25 Revised:2014-10-10 Online:2014-12-08 Published:2014-11-28

Abstract:

Water-soluble polysaccharides from traditional Chinese medicine (TCM) have properties of broad-spectrum treatment and low toxicity, making them as important components in natural medicines and health products. In order to solve the problem of polysaccharides characterization caused by their complex structures, a "bottom-up" approach was developed to complete the characterization of polysaccharides from Astragalus. Firstly, Astragalus pieces were extracted with hot water and then were precipitated by ethanol to obtain Astragalus polysaccharides. Secondly, a partial acid hydrolysis method was carried out and the effects of time, acid concentration and temperature on hydrolysis were investigated. The degree of hydrolysis increased along with the increase of hydrolysis time and acid concentration. The temperature played a great role in the hydrolysis process. No hydrolysis of the polysaccharides occurred at low temperature, while the polysaccharides were almost hydrolyzed to monosaccharide at high temperature. Under the optimum hydrolysis conditions (4 h, 1.5 mol/L trifluoroacetic acid, and 80 ℃), Astragalus polysaccharides were hydrolyzed to characteristic oligosaccharide fragments. At last, a hydrophilic liquid chromatography-mass spectrometry method was used for the separation and structural characterization of the polysaccharide hydrolysates. The results showed that the resulting polysaccharides were mainly 1→4 linear glucan, and gluco-oligosaccharides with the degrees of polymerization (DP) of 4-11 were obtained after partial acid hydrolysis. The significance of this study is that it is the guidance for the characterization of other TCM polysaccharides.

Key words: Astragalus, characterization, hydrophilic interaction liquid chromatography (HILIC), mass spectrometry (MS), partial acid hydrolysis, polysaccharides

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