Structrual Analysis Of Polysaccharide From Astragalus And Its Anti-Tumor Activity

The crude polysaccharide was extracted by boiled water and precipitated by ethyl alcohol from Radix Astragalus. The protein was removed by Sevag which companied with enzyme; pigment was eliminated through washing by ethyl alcohol. Two kinds of polysaccharide APS-Ⅰ and APS-Ⅱ were obtained after purified by fractional precipitation used ethyl alcohol and DEAE-Sephadex A-25and Sephadex G-100elution by water. The total sugar content of each polysaccharide was94.59%and97.57%. There were no absorption in UV spectrum indicated that both APS-Ⅰ and APS-Ⅱ were not contained protein and nucleic acid; The optical rotation measured results showed that the optical rotation was [a]DAPS-Ⅰ23℃=+185°(C,0.001g/mL, H2O) and [a]DAPS-Ⅱ23℃=+170°(C,0.001g/mL, H2O) respectively. The molecular weight of APS-Ⅰ and APS-Ⅱ were4.77×106and8.68×103Da respectively that determined by HPLC.Monosaccharide analysis indicated that APS-Ⅰ and APS-Ⅱ mainly composed by glucose, also a spot of arabinose and xylose. The molar ratio of arabinose:xylose: glucose of APS-I and APS-Ⅱ were0.54:1:18.14and0.23:1:29.39separately. IR. Methylation、Periodate oxidation、Smith degradation、1HNMR and13CNMR were used on the structure analysis of APS-Ⅰ and APS-Ⅱ. The results indicated that APS-I and APS-Ⅱ have the similar structure; the main chain is mainly made up of major a-(1→3) glucose and a little1→4、1→6glucose、arabinose and xylose composed the side chain. The difference of APS-Ⅰ and APS-Ⅱ was that they have different molecular weight, namely the difference of the polymerization degree of polysaccharide chain.Through the research about anti-tumor activity、SDS-PAGE of mice serum proteins and tumor tissue slice observation showed us that the tumor inhibition rate of APS-I and APS-Ⅱ were55.47%and47.72%respectively; and the anti-tumor activity of APS-Ⅰ is better than APS-Ⅱ.That illustrated the anti-tumor activity of polysaccharide from Astragalus was related to structure.