Chemical characterization and in vitro antitumor activity of a single-component polysaccharide from Taxus chinensis var. mairei

An alkali-soluble single-component polysaccharide, named CPTC-2, was isolated and purified from the leaves of Taxus chinensis var. mairei. by ion-exchange and gel-permeation chromatography in series. The weight-average molecular mass (Mw) of CPTC-2 was about 73.53 kDa determined by gel permeation chromatography (GPC). The structural characteristics of CPTC-2 were analyzed by gas chromatography (GC), Infrared (IR) spectrum, nuclear magnetic resonance (NMR) spectroscopy, periodate oxidation and Smith degradation studies, as well as methylation analysis. The results showed that CPTC-2 consisted of glucose, mannose, xylose, arabinose, rhamnose, and galactose with a molar ratio of 1.00:0.32:0.27:3.34:1.22:1.84. CPTC-2 was mainly composed of one type of sugar, α-glycosidic linkage. It had a backbone composed of α-(1 → 3) Araf, α-(1 → 5) Araf and α-(1 → 4) Galp with branches composed of α-(1 → 3,5) Araf and β-(1 → 3,6) Manp. In vitro anti-tumor experiments with SGC-7901 cells were performed and assessed by MTS (MPEG-2 Transport Stream) method and flow cytometry. The results showed CPTC-2 could inhibit the growth of SGC-7901 cells in a concentration-dependent manner via increased apoptosis. The relationship between the structure of CPTC-2 and its anti-tumor activity indicated that the α-configuration glycosidic bond residues may be essential for the anti-tumor activity of this polysaccharide.