Structural analysis of a bioactive polysaccharide, PISP1, from the medicinal mushroom Phellinus igniarius

PISP1, a heteropolysaccharide isolated from fruiting bodies of Phellinus igniarius by hot aqueous extraction and purified by DEAE-Sepharose anion-exchange and gel filtration chromatography, is composed of fucose, galactose, mannose, and 3-O-Me-galactose in a ratio of 1:2:1:2. Methylation, monosaccharide analysis, and NMR studies (1H NMR, 13C NMR, COSY-45 degrees , TOCSY, ROESY, HSQC, and HMBC) revealed that PISP1 had a backbone consisting of 1,6-disubstituted-3-O-Me-alpha-D-galactopyranosyl residue, 1,3,6-trisubstituted-alpha-D-manopyranosyl residue, 1,4-disubstituted-alpha-D-galactopyranosyl residue, and 1,2-disubstituted-alpha-D-galactopyranosyl residue, and had a 1-substituted-alpha-L-fucopyranosyl terminal attached to O-3 of a manopyranosyl residue. Preliminary bioactivity tests conducted in vitro revealed that PISP1 stimulated the proliferation of mouse spleen lymphocytes.