Isolation,Structural Characterization And Anti-tumor Activity Of One-component Polysaccharides From Taxus Chinensis

Taxus chinensis belongs to the level of protection of rare tree species in China. Since taxol which has a strong antitumor activity was extracted from Taxus chinensis, Taxus chinensis has become the research hot spot. After been extracted with taxol, Taxus chinensis was mostly abandoned, which caused great waste of resource. Therefore, people gradually put their eyes on the study of the other bioactive components in Taxus chinensis, such as terpenoids, alkaloids, flavonoids, polysaccharides and so on. In this paper, we focus on the alkali-soluble bioactive macromolecular compound-polysaccharides and study the isolation and purification, structural characterization and anti-tumor activity of one-component polysaccharides from the leaves and branches of Taxus chinensis.1、In the extaction process, we adopted alkali to extract the polysaccharides. The best alkali extraction conditions were obtained by single factor test and orthogonal test:so lid-to-liquid ratio 1:20 (g/mL), extraction time 120 min, lye concentration 1.0 mol/L, and extracting temperature 75℃. Under the optimal combinations, the yield of polysaccharide was 3.45%.2、In the isolation and purification processes, crude polysaccharides were separated by DEAE Sepharose Fast Flow ion exchange resin, and three fractions were obtained, named CPTC-1, CPTC-2 and CPTC-3 respectively. CPTC-1 and CPTC-2 were further isolated and purified by gel chromatography, and CPTC-1a, CPTC-1b and CPTC-2 were obtained with high purity.3、In the processes of structural analysis, the weight-average molecular weight of CPTC-1a, CPTC-1b and CPTC-2 were 135276 Da,8862 Da and 73527 Da respectively determined by GPC (Gel permeation chromatograp). The structure characteristic of these three kinds of polysaccharides were analyzed by GC, IR, NMR, periodate oxidation and smith degradation studies, methylation analysis and AFM (Atomic force microscope). The results show that CPTC-1a, CPTC-1b and CPTC-2 consisted of glucose, mannose, xylose, arabinose, rhamnose, galactose with the molar ratio of 1.00:0.63:0.17:4.32:0.332.08 (CPTC-1a); 1.00:0.53:0.21:3.70:0.55:2.20 (CPTC-lb); 1.00:0.32:0.273.34:1.22:1.84 (CPTC-2). These three kinds of polysaccharides were mainly composed of one type of sugar, α-glycosidic linkage. They had a backbone composed of α-(1→3) linked arabinose and α-(1→4) linked galactose with the branch composed of β-(1→3,5) linked arabinose and β-(1→3,6) linked mannose, and the non-reducing end-units were mainly composed of arabinose, glucose, galactose and xylose. In CPTC-1a and CPTC-2, polysaccharide chains winded into spherical particles; CPTC-1b presented multiple chain structures and rodlike strictures.4. The anti-tumor experiments of SGC-7901 cells (the human gastric cancer cells) were achieved by the methods of MTS and flow cytometry, and the results show that these three kinds of polysaccharides could inhibit the growth of SGC-7901 cells with a concentration-dependent manner and this process was realized by encouraging apoptosis. In addition, we find that the combined utilization of CPTC-2 and 5-FU (5-fluorouracil) could significantly increased the anti-tumor activity of 5-FU. Therefore, one-component polysaccharides from Taxus chinensis have the potential to be effective auxiliary agents of chemotherapy drugs.