Studies on fungal polysaccharides. XXVII. Structural examination of a water-soluble, antitumor polysaccharide of Ganoderma lucidum.

Abstract

A water-soluble, antitumor polysaccharide GL-1, .**GRAPHIC**. + 26.degree. (c = 1, water), MW 40,000, was isolated from the fruit bodies of Ganoderma lucidum (Rokkakushi, a kind of Reishi). GL-1 consists of glucose, xylose and arabinose in the molar ratio of 18.8:1.5:1.0. Structural examination was carried out by periodate oxidation, Smith degradation, methylation analysis, partial acid hydrolysis and .alpha.-amylase treatment. GL-1 is a branched arabinoxyloglucan containing backbone and side-chains involving D-glucopyranosyl (1 .fwdarw.4)-.alpha. and -.beta.-, -.beta.-, (1 .fwdarw. 6)-.beta.- and (1 .fwdarw. 3)-.beta.-linkages. Arabinose is present as a part of the non-reducing terminal residues, and xylose may be present as a part of the side-chain. GL-1 strongly inhibited the growth of mouse Sarcoma 180 solid-type tumor (inhibition ratio, 95.6-98.5%) when injected i.p. (20 mg/kg) for 10 days. Mild acid hydrolysis and .alpha.-amylase treatment of GL-1 had no effect on the antitumor activity. The essential structure for the antitumor activity of GL-1 is probably a branched glucan core (GL-3) involving (1 .fwdarw. 3)-.beta.-, (1 .fwdarw. 4)-.beta.- and (1 .fwdarw. 6)-.beta.-linkages.