Chemical components and molecular mass of six polysaccharides isolated from the sclerotium of Poria cocos

Abstract

Six polysaccharides were extracted sequentially from the fresh sclerotium of Poria cocos cultivated in China using 0.9% NaCl (PCS1), hot water (PCS2), 0.5 M NaOH (PCS3-I and PCS3-II), and 88% formic acid (PCS4-I and PCS4-II). Their chemical and physical characteristics were determined using infrared spectroscopy (IR), gas chromatography (GC), GC–MS methylation analysis, 13C NMR spectroscopy, elementary analysis (EA), protein analysis, size exclusion chromatography combined with laser light scattering (SEC-LLS), light scattering (LS), and viscometry. The results indicated that the polysaccharides PCS1, PCS2, and PCS3-I were heteropolysaccharides containing d-glucose, d-galactose, d-mannose, d-fucose, and d-xylose; the predominant monosaccharide was d-glucose except for PCS1 where it was d-galactose. PCS3-II, the main component of the sclerotium of P. cocos, was a linear (1 → 3)-β- d-glucan of high purity. PCS4-I consisted of (1 → 3)-β- d-glucan with some β-(1 → 6) linked branches. PCS4-II was mainly composed of (1 → 3)-β- d-glucan containing some glucose branches. The M w values of the six polysaccharides PCS1, PCS2, PCS3-I, PCS4-I in 0.2 M NaCl aqueous solution, PCS3-II, and PCS4-II in dimethyl sulfoxide (Me 2SO) were determined to be 11.6 × 10 4, 20.8 × 10 4, 17.1 × 10 4, 9.1 × 10 4, 12.3 × 10 4, and 21.1 × 10 4, respectively. The six polysaccharides in aqueous solution or Me 2SO exist as flexible chains.