Structure, molecular conformation, and immunomodulatory activity of four polysaccharide fractions from Lignosus rhinocerotis sclerotia

Four polysaccharide fractions, LRP-1, LRP-2, LRP-3 and LRP-4 were extracted stepwise from Lignosus rhinocerotis sclerotia with distilled water at 25, 95, 120 degrees C and 1.0M NaOH solution at 4 degrees C. Their structure, molecular size and chain conformation were clarified using SEC-MALLS-RI, GC, FT-IR and UV-vis. Furthermore, their immunomodulatory activities were evaluated by the model of cyclophosphamide (Cy)-induced immunosuppression. The LRP-1 and LRP-2 were polysaccharide-protein complexes (46-68% beta-D-glucan and 27-48% protein), while LRP-3 and LRP-4 were absolutely composed of beta-D-glucose. The LRP-4 with low polydispersity had much higher molecular weight (M-w, 5.86 x 10(6) g/mol) and intrinsic viscosity ([eta], 202.6 ml/g) than other LRP fractions. Based on M-w, radius of gyration ((1/2)(z)) and [eta] data with the exponent,8 of (1/2)(z)-M-w and its U-shaped curve, all four LRP fractions were highly branched macromolecules and LRP-3 showed a more compact sphere-like conformation than LRP-2 in aqueous solution. Additionally, all four LRP fractions exhibited protective effects against Cy-induced immunosuppression in mice by improving immune organs as well as stimulating the release of major cytokines TNF-alpha and INF-gamma. This work provides a theoretical basis for the application of polysaccharides and their protein complexes from Lignosus rhinocerotis sclerotia in food- or drug-based therapies. (C) 2016 Elsevier B.V. All rights reserved.