A minor, protein-containing galactomannan from a sodium carbonate extract of Cordyceps sinensis

Abstract

A water-soluble, minor, protein-containing galactomannan (CT-4N), [α] D −29.6°, isolated from a 5% sodium carbonate extract of Cordyceps sinensis, showed a homogeneous pattern in gel filtration and one spot in glass-fiber paper-electrophoresis. The molecular weight was estimated by gel filtration to be ∼23,000. It was mainly composed of d-mannose and d-galactose in the molar ratio of 3:5, and contained a small proportion of protein. From the results of methylation analysis, Smith degradation, stepwise hydrolysis, and 13C-n.m.r. spectroscopy, it was concluded that the polysaccharide has a highly branched structure, and is composed of (1→6)- and (1→2)-linked α- d-mannopyranosyl residues in the main chain. Some of the residues are present as branching points of (1→2,6) and (1→4,6) linkages and the branches contain short chains having a large proportion of (1→5)-linked β- d-galactofuranosyl residues and a small proportion of (1→6)-linked α- d-galactopyranosyl resdues, and the (nonreducing) terminal groups consist of a large proportion of β- d-galactofuranosyl and a small proportion of α- d-mannopyranosyl groups.