Polysaccharides from the fruit bodies of the basidiomycete Laetiporus sulphureus (Bull.: Fr.) Murr

Abstract

The two main polysaccharides from the basidiomycetous fungus Laetiporus sulphureus were isolated, purified and characterized. The structural assignments were carried out using (13)C, (1)H, and (1)H,(13) HSQC nuclear magnetic resonance spectroscopy, methylation analysis, and Smith degradation. One was a linear beta-glucan having a (1-->3)-linked main chain, namely laminaran. The other was a fucomannogalactan, which consisted of a main chain of (1-->6)-linked alpha-D-galactopyranosyl residues, a part of them being substituted at O-2 by 3-O-D-mannopyranosyl-L-fucopyranosyl, alpha-D-mannopyranosyl and in a minor proportion, alpha-L-fucopyranosyl groups. This heteropolysaccharide is related to those of other Basidiomycetes heterogalactans, although it differs distinctly in its side-chain structures. Whereas part of the single-unit L-fucopyranosyl and/or 3-O-alpha-mannopyranosyl-L-fucopyranosyl residues are present as side chains of the other heterogalactans, additional alpha-D-mannopyranosyl units are present in our fucomannogalactan of L. sulphureus.