Polysaccharides in fungi. XXVI. Two branched (1----3)-beta-D-glucans from hot water extract of Yu ĕr.

Two water-insoluble glucans, U-3-N ([alpha]D +1.0 degree, 0.5 M sodium hydroxide) and U-3-AP1 ([alpha]D +2.5 degrees, 1 M sodium hydroxide) were isolated from hot-water extract of the fruiting bodies of Yũ ĕr (Chinese name) (Auricularia sp.). U-3-N and U-3-AP1 were investigated by a combination of chemical and spectroscopic methods. The results indicated that U-3-N (molecular weight, 6.1 x 10(5)) was similar to beta-(1----6)-branched (1----3)-beta-D-glucan (N-5P: molecular weight, 5.6 x 10(5)) isolated from the alkaline extract of the fruiting bodies, and U-3-AP1 (molecular weight, 6.3 x 10(4)) was beta-(1----6)-branched (1----3)-beta-D-glucan containing beta-(1----6)-linked D-glucopyranosyl residues. U-3-N showed potent anti-tumor activity against the solid form of sarcoma 180, although U-3-AP1 had little effect on the tumor.