Heteroglycans from the fruiting bodies of Agrocybe cylindracea: Fractionation, physicochemical properties and structural characterization

Polysaccharide from Agrocybe cylindracea has been demonstrated to exhibit excellently biological functions, but insufficient understanding of its physicochemical property and fine structure limits its wide application and development. In the present study, two water-soluble heteroglycans, a high molecular weight (SACP-40) and a low molecular weight (SACP-80), were isolated from the fruit bodies of A. cylindracea by hot water extraction and gradient ethanol precipitation. There was little difference in their physicochemical properties, including major chemicals and monosaccharide compositions. Rheological measurements revealed SACP-80 was a typical pseudoplastic fluid with shear thinning behavior at the concentration of 3.0%, whereas exhibited a near-Newtonian fluid at lower concentration. SEM observation suggested SACP-80 showed micro-spherical shapes loosely attached to fibrous filament in its surface. Besides, methylation and 1D/2D NMR analysis indicated that SACP-80 was a branched heteroglycan with a backbone composed of β-(1 → 6)-glucopyranosyl, α-(1 → 6)-galactopyranosyl and α-(1 → 2,6)-glucopyranosyl residue at a ratio of 3:1:1. This work provides a theoretical basis for gaining insight into the relationship between the fine structure and viscosity of polysaccharide from A. cylindracea, which could further guide its functional studies and advance the potential application in food and biomedicine industries.