Preparation, structural characterization and biological activities of Laetiporus sulphureus polysaccharide and its stabilized selenium nanoparticles

The total polysaccharides extracted from Laetiporus sulphureus fruiting bodies by ultrasound-assisted complex enzyme method were separated by freeze–thaw combined with fehling reagent to prepare purified polysaccharide (LSPS1). The results of monosaccharide composition and molecular weight distribution demonstrated that LSPS1 contained galactose (51.83%), mannose (26.89%), fucose (16.13%) and glucose (5.15%), and the molecular weight was around 17.3 kDa. Methylation analysis indicated that the backbone of LSPS1 consisted of 1,6-Galp residues, branched at O-2 of Galp with t-Manp, t-Fucp and t-Glcp residues as side chains. In addition, LSPS1 was used for the synthesis of SeNPs based on the redox system of sodium selenite and ascorbic acid. The L. sulphureus polysaccharide selenium nanoparticles (LSPS1–SeNPs) were characterized by UV, FT-IR, ICP-MS, EDX, DLS and SEM, inferring that LSPS1–SeNPs were stabilized with spherical and granular surface structure as well as a mean particle size of 96.72 ± 1.12 nm. Both of LSPS1 and LSPS1–SeNPs possessed strong antioxidant and hypoglycemic activities while the effects of LSPS1–SeNPs were superior to LSPS1. The findings provided valuable structural information for L. sulphureus polysaccharide, and will promote the application of SeNPs by L. sulphureus polysaccharide in potential antioxidant agent and hypoglycemic candidate.