Isolation and Characterization of Polysaccharides of “Kikurage,” Fruit Body ofAuricularia auricula-judae

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Abstract
Two kinds of β-d-glucans and an acidic heteropolysaccharide were isolated from the fruit body of Auricularia auricula-judae, and their structural features were elucidated. A water soluble glucan ([α]D–10°) consists of a backbone chain of β-(1→3)-linked d-glucose residues, two out of three glucose residues being substituted at the C–6 positions with single glucose units. The other glucan, which was obtained as the hot alkali insoluble residue, is also β-(1→3)-glucan with single branches at C–6 positions, but it has an extremely highly branched structure; a small proportion of (l→6)-internal linkages may be situated in the side chains. An acidic heteropolysaccharide ([α]D –20°), isolated from the hot water extract through insoluble complex formation with cetylpyridinium chloride, contains d-xylose, d-mannose, d-glucose and d-glucuronic acid (molar ratio, 1.0: 4.1:1.3: 1.3). Methylation followed by acid hydrolysis of the polysaccharide yielded 2,3,4,6-tetra-O-methyl-d-mannose(glucose), 2,3,4-tri-O-methyl-d-xylose, 2,4,6-tri-, 4,6-di-, and 2,4-di-O-methyl-d-mannose, 2,4-di-O-methyl-d-glucose, together with 2,3,4-tri-O-methyl-d-glucuronic acid, suggesting that it consists of a backbone chain of (1→3)-linked mannose residues, which are attached with d-xylose, d-mannose and d-glucuronic acid residues at the C–2 or C–6 positions. On the basis of these findings, the constitution of the A. auricula-judae was compared with that of Tremella fuciformis.