Abstract
Polysaccharides in the hot water extract of the fruit bodies of G. frondosa contain α-1, 4-, α-1, 6-, β-1, 6-and β-1, 3-glucosidic linkages, and include an antitumor-active substance assumed to be a β-1, 3-glucan (N. Ohno et al., Chem. Pharm. Bull., 32, 1142 (1984)). In this paper, the purification and structural characterization of this glucan are described. Prior to the hot water extraction, the fruit bodies were digested with amylases, in order to decrease the content of α-1, 4-glucan in the fruit body. After the treatment, the fruit bodies were extracted with hot water, cold sodium hydroxide, and then hot sodium hydroxide, successively. Antitumor β-1, 3-glucan in the hot water extract was purified by using diethylaminoethyl (DEAE)-Sephadex A-25 column chromatography and stepwise precipitation with ammonium sulfate. The purified glucan had [α]D +6.3 (H2O), and an average molecular weight of 5.6×106 (8M urea-0.2N NaOH), and shifted λmax of Congo Red to 500 nm (0.1N NaOH). From the results of methylation analysis and carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy, this glucan was concluded to be a branched β-1, 3-glucan possessing a branch at position 6 of every third main-chain glucosyl unit.
