Structural elucidation and immuno-stimulating activity of an acidic heteropolysaccharide (TAPA1) from Tremella aurantialba

A novel acidic heteropolysaccharide (TAPA1) was purified from hot water extracts of Tremella aurantialba fruiting bodies by DEAE-Sepharose Fast Flow and Sephacryl S-500 High-Resolution Chromatography. The heteropolysaccharide had a molecular weight of ca. 1.35 x 10(6) Da, and a carbohydrate content estimated to be -98.7% by the phenol-sulfuric acid method. It was composed mainly of D-mannose, D-xylose, and Dglucuronic acid in the ratio of ca. 5:41, along with trace amounts of D-galacturonic acid and D-glucose. Monosaccharide compositional analysis and GC-MS of methylated derivatives, combined with H-1 and C-13 NMR spectroscopies (including COSY, TOCSY, NOESY, HSQC, and HMBC spectra), revealed TAPA1 to consist of an alpha-(1 -> 3)-linked mannopyranosyl backbone, partially substituted at position 4 with xylose side chains, and at position 2 with side chains composed of either xylose, mannose, and glucuronic acid or of xylose and mannose. Bioactivity testing showed that TAPA1 stimulated the proliferation of mouse spleen lymphocytes in vitro. (C) 2009 Elsevier Ltd. All rights reserved.