Structure and antitumor activities of the water-soluble polysaccharides from Ganoderma tsugae mycelium

Six water-soluble polysaccharides coded as GTM1 to GTM6 were extracted sequentially from the mycelium of Ganoderma tsugae with 0.2 M sodium phosphate buffer solution at 25, 40, and 80 degreesC, water at 120 degreesC, 0.5 M sodium hydroxide at 25 and 65 T. The chemical structures were determined by using IR, EA, GC and C-13 NMR. The weight-average molecular mass (M-w) was characterized by size exclusion chromatography combined with laser light scattering (SEC-LLS). The results indicated that the samples GTM1 and GTM2 were heteropolysaccharide-protein complexes with the protein content of 13.5 and 20.1%, and apparent-mean M-w of 62.8 x 10(4), 81.8 x 10(4), respectively. GTM3 and GTM4 contained (1 --> 3)-beta-D-glucans and (1 --> 4)-alpha-D-glucans, while GTM5 and GTM6 were mainly a (16)branched (1 --> 3)-alpha-D-glucan. Two peaks were found in the SEC patterns of the four samples GTM1 to GTM4, representing fractions 1 composed of branched (1 --> 4)-alpha-D-glucan with high M-w and fraction 2 composed of galactose, glucose and mannose with relatively low M-w. With the progress of isolation, the content of fraction 2 decreased from 90.2 to 57.1%, accompanying with enhancing antitumor activity. The polysaccharides GTM1. GTM2 and GTM3 had significantly higher antitumor activity against solid tumor Sarcoma 180 with the inhibition ratio beyond 50%. The results suggested that the effects of the moderate content of galactose and bound protein, as well as relatively lower M-w on the improvement of antitumor activities of polysaccharides could not be negligible. (C) 2004 Elsevier Ltd. All rights reserved.