The presence of partially 3-O-methylated mannogalactan from the fruit bodies of edible basidiomycetes Pleurotus ostreatus 'florida' Berk. and Pleurotus ostreatoroseus Sing

The partially 3-O-methylated mannogalactans were isolated from the fruiting bodies of edible basidiomycetes Pleurotus ostreatus 'florida' Berk. and Pleurotus ostreatoroseus Sing. They were obtained via successive aqueous extraction, freeze thawing, and precipitation with Fehling solution and then investigated using (13)C- and (1)H-nuclear magnetic resonance spectroscopy (including COSY, TOCSY and HMQC techniques), methylation analysis and Smith degradation. The main chain consisted of (1-->6)-linked alpha-D-galactopyranosyl residues containing 3-O-Me-alpha-D-galactopyranoses, a part of these units being substituted in the position O-2 with beta-D-mannopyranose residues. The heteropolysaccharides found were similar with differences only in the levels of the 3-O-Me-alpha-D-galactopyranoses residues. The presence of partially 3-O-methylated mannogalactan appears to be typical of Pleurotus spp.