Indian Journal of Chemistry Vol. 38B, June 1999, pp. 709-712 Structural studies on a polysaccharide from an edible mushroom, Termitomyces eurhizus Amar Pramanik & Syed Sirajul Islam* Department of and Chemical Technology, Vidyasagar University, Midnapore 721102, West Bengal, India Received 20 May 1998; accepted (revised) 7 April 1999 A po ly saccharide (PS), isolated from the hot aqueous ex trac t of the mushroom, Temlitomyces eurhiZ lIs, is found to contain, D-glucose, D-galactose, D-mannose and D-galac turonic acid in a mole ratio of about 0.9:0.9: 1.0:0. 9. From the peiiodate oxidation and meth ylati on analy sis of th e PS , the linkages among the constituent sugar resi dues are identified as, D-Galp (1,6 linked), D- Manp (1 ,2,3 linked), D-G1cp (1,3 linked) and D-galacturonic acid. The anomeric configuration of the constituent sugar residues are detennined by the chromium trioxide oxidation studies of the acetylated polysaccharide. It is concluded that galactose and mannose have the f)-configuration while glucose and galacturonic acid have the a-configuration. Based on the above observations, the structure of the repeating unit of th e polysaccharide was assigned as, -6)-f)-o-Galp-( 1-3)-f)-o-Manp-( 1-3)-a-o-G1cp-( I- I (2 -1 )-a-o-GalpA Five mushroom of the genus Termitomyces, namely Termitomyces eurhizu s, T. microcarpus, T. robustu s, T. straitus, and T. clypeatus have since been identified as edible mushroom with high nutritive value. T. ro bustus and T. clypeatus contained I 31 % protein, 32% carbohydrate and 10-14% ascorbic acid. Several enzymes of high therapeutic value have been reported in the species T. mic ro carpui and T. clypeatus 3 . 7 • Nutrient content of T. robustuS 8 . 9 was analyzed and found to contain free amino acids, protein, glycogen, lipid, sugar and ascorbic acid and trace minerals in varying proportions. T. eurhizus 10 obtained from liquid culture medium was found to contain protein, 14-27% (in dry wet basis), ten amino acids of which have been identified previously. This mus.hroom grows on the laterite soil of the forest region of Bankura and Midnapore district of West Bengal. It is abundantly available during the months of Sept.-Oct. and local people consume them as delicious and edible mushroom. No work has been reported on the polysaccharide isolated from the aqueous extract of this mushroom. Therefore a detailed investigation was carried out on the PS of this mushroom and the results are reported in this paper. Results and discussion The purified PS had + 11 0 ; Total sugars (98%) were estimated by phenol-sulphuric acid method I I and acid sugar was estimated as 24% by carbazole-sulphuric acid method 12 • The PS was hydrolyzed with 2M trifluoroacetic acid with inositol as the internal standard. The hydrolyzed PS on paper chromato graphic analysis, showed the presence of D- glucose, D-galactose, D-mannose and D-galacturonic acid. Alditol acetates of the hydrolysate on analysis with GLC showed D-glucose, D-galactose, and D- man nose in almost equimolar ratio. D-galacturonic acid was estimated as 24% by carbazole-sulphuric acid method (Table I). Carboxyl-reduced 13 PS on hydrolysis and followed by GLC examination of the corresponding alditol acetates showed the presence of D-glucose, D-galactose and D-mannose in a mole ratio of almost 1:2: 1. The increase in the mole ratio of galactose further indicated that, D-galcturonic acid Table I-Sugar content of the PS of Termilomyces eurhizus. PS RPS mole mole mole mole % ratio % ratio Galactose 23 .5 0.9 48.0 1.9 Glucose 24.5 0.9 24.5 0.9 Mannose 26.0 1.0 25.5 0.9 Galacturonic-acid 24.0 0.9 PS: Polysaccharide isolated from aq. extract of the mushroom, Termilomyces eurhizus. RPS: Carboxyl-reduced polysaccharide of this mushroom.