Structural features and antitumor activity of a novel polysaccharide from alkaline extract of Phellinus linteus mycelia

A novel high molecular weight polysaccharide (PL-N1) was isolated from alkaline extract of the cultured Phellinus linteus mycelia. The weight average molecular weight (Mw) of PL-N1 was estimated at 343,000 kDa. PL-N1 comprised arabinose, xylose, glucose, and galactose in the molar ratio of 4.0:6.7:1.3:1.0. The chemical structure of PL-N1 was investigated by FTIR and NMR spectroscopies and methylation analysis. The results showed that the backbone of PL-N1 comprised (1 → 4)-linked β-D-xylopyranosyl residues, (1 → 2)-linked α-D-xylopyranosyl residues, (1 → 4)-linked α-D-glucopyranosyl residues, (1 → 5)-linked β-D-arabinofuranosyl residues, (1 → 4)-linked β-D-xylopyranosyl residues which branched at O-2, and (1 → 4)-linked β-D-galactopyranosyl residues which branched at O-6. The branches consisted of (1 → )-linked α-D-arabinofuranosyl residues. Antitumor activity assay in vitro showed that PL-N1 could inhibit the growth of HepG2 cells to a certain extent in a dose-dependent manner. Thus, PL-N1 may be developed as a potential, natural antitumor agent and functional food.