Structural analysis and anti-tumor activity comparison of polysaccharides from Astragalus

Two polysaccharides: APS-I and APS-II, were obtained after a successive purification consisting of (1) fractional precipitation using ethyl alcohol; (2) filtration through DEAE-Sephadex A-25 and Sephadex G-100 eluted by water. The molecular weights of APS-I and APS-II were 4.77 × 106 and 8.68 × 103 Da, respectively, and they were mainly composed of glucose, and a small amount of arabinose and xylose, with their molar ratios of 0.54:1:18.14 and 0.23:1:29.39, respectively for APS-I and APS-II. FTIR, methylation, periodate oxidation, Smith degradation, 1H NMR and 13C NMR were used in their structure analysis. The results indicated that structurally, APS-I and APS-II were similar, with their main chains mainly composed of major α-(1 → 3) glucose and a few 1 → 4, 1 → 6 glucoses, while the side chain contained arabinoses and xyloses. The tumor inhibition ratios of APS-I and APS-II were 55.47% and 47.72%, respectively.