A hyperbranched β-d-glucan with compact coil conformation from Lignosus rhinocerotis sclerotia

An alkali-soluble polysaccharide was extracted from Lignosus rhinocerotis sclerotia (LRP). Its structural characteristics were determined by GC-MS, FT-IR, GC, 1D and 2D NMR combined with Smith degradation and methylation analysis. The LRP had a (1→3)-β-d-Glcp backbone with every three residues bearing a (1→6)-linked and hyperbranched side chain that contained three (1→6)-β-d-Glcp residues as secondary main chain and two terminal β-d-Glcp residues linked at O3. The degree of branching was 0.76 from GC-MS analysis, implying a highly branched structure for LRP. The M_w, 2>_z^1/2, R_h and [η] values of LRP in 0.25M LiCl/DMSO were measured by SEC-MALLS-Vis-RI combination technology to be 2.88×10⁵g/mol, 30.36nm, 22.34nm and 131.50ml/g, respectively. Furthermore, the exponent α of [η]-M_w, β of 2>_z^1/2-M_w, the fractal dimension d_f and molecular parameter ρ were determined to be 0.20, 0.33, 2.50 and 1.36, demonstrating that the LRP was a hyperbranched polysaccharide and adopted a compact coil conformation in LiCl/DMSO.