Purification Structural Investigation And Antitumor Effect Of Polysaccharide From Taxus Chinensis Var. Mairei

Yew (Taxus sp.) is a rare species of plant, which has a long history. Since taxol was extracted from the barks, leaves and branches of Taxus, it has attracted more and more attention. But according to the current process, a lot of residues were left after extraction. However, many different kinds of bio-active components, such as terpenoids, flavonoids and alkaloids, remained in the residue. Recently, we also initially isolated and purified polysaccharides from the leaves of Taxus maire, which have not reported in literatures.In this work, purification, structure analysis and antitumor activity of the polysaccharides were investigated. After extracted from the leaves of Taxus mairel with hot water, the crude polysaccharides were decolorized with three methods including solution of H2O2, normal anion exchanger chromatograph and macroporous resin adsorption chromatograph. Under the optimized operating conditions for H2O2 decolorization were 15% concentration, pH 9.0, 40℃ and 40min retention time, the ratios of decolorization and polysaccharides retention were 60.4% and 84.7%, respectively. Anion exchange resin Purolite A500P, polar adsorption resin Amberlite XAD7HP and nonpolar resin NKA and X5 also showed the good results of decolorization. The optimized operating conditions for decolorization with both anion exchange and adsorption chromatography were as follows: pH 5.9, 35℃, 150 min retention time under static adsorption or flow rates: 5BV/hr both for XAD7HP and NKA, 1BV/hr for X5 under dynamic absorption. After that, 4 kinds of polysaccharides (named PCH1, PCH2,PCH3 and PCH0.5) were fractionated by ethanol precipitate, followed by DEAE-Sepharose FF anion exchange chromatography and Sephadex G-25 desalinisation. Then, the structure and chemical component of the aforementioned polysaccharides were studied by chemical and instrumental analysis. The results showed that the average Mw of the 3 kinds of polysaccharides were 5.8×10~-3D 5.43×10~4KD 和 1.78×10~5D, respectively. The PCH0.5 which consists of branched chains, is composed of 2,4-Methoxye-Man, 2--deoxyl-glc, D-Xly(a), D-Xly(p), D-Ara and D-Man with ratio of 2:6:28:9:3:3:49 andcontains both a and P deviating vibration of C-H as pyranoses. Experiments on pharmacological effects of mice indicated that the total four aforementioned polysaccharides have great activities in inhibiting the tumor growth, increasing hypoxic tolerance, improving the immune function and raising the life-prolonging rate.