Structural characterization and in vitro antitumor activity of a novel polysaccharide from Taxus yunnanensis

The shrub, Taxus yunnanensis is famed as the source of the important anticancer drug, paclitaxel. But research on its polysaccharides contents has been scarce. The present research aimed to investigate the polysaccharide content of T. yunnanensis leaves and study the antitumor activities of isolated polysaccharide(s) using human tumor cells (K-562 and MCF). A novel heteropolysaccharide (TMP70W) was isolated and purified by anion-exchange and gel-permeation chromatography. Its molecular weight was 36.94 kDa and structural features were elucidated by partial acid hydrolysis, periodate oxidation-Smith degradation, methylation analysis, GC-MS, HPAEC-PAD, FT-IR, and NMR. The repeating unit of TMP70W had a backbone composed of (1→5)-linked-α-l-Araf, (1→2,5)-linked-α-l-Araf, and (1→6)-linked-β-d-Galp with a branch of α-d-Glcp-(1→2)-α-d-Galp-(1→ at the position of C-2 of arabinose. TMP70W displayed mild cytotoxicity against K562 cells with the IC50 value of 39.63 ± 2.37 μg/mL and inhibitory activity against MCF-7 cells (32.08 ± 0.39% at the concentration of 400 μg/mL) in a concentration-dependent manner.