Extraction, Isolation, Structure Identification And Antioxidant Research Of Polysaccharide From Velvet Mushroom Fruit Body

Lyophyllum decastes Sing.,also known as antler mushroom,is a precious edible medicinal fungus.At the same time,the fruiting body is used as a traditional medicine,its main ingredient is polysaccharide?LDS?,which has a series of important biological activities,such as anti-tumor,hypoglycemic and hypolipidemic,anti-oxidant.By analyzing the conventional nutrient composition from the fruiting bodies of L.decastes,it showed that the fruiting body of L.decastes showed high protein and low fat?crude protein 22.16%,crude fat 2.69%?,which was similar to the literature report.Three polysaccharide fractions?LDS30,LDS60 and LDS80?were obtained by ethanol gradient precipitation,the content of polysaccharide in LDS60 was the highest,which was 48.58±4.141%.The High-speed shearing homogenization extraction process of L.decastes polysaccharide was optimized by Box-Benhnken response surface design.The optimum conditions were predicted as follows:ratio of water to material18 mL/g,rotate speed 9500r/min,extraction time 2.3 min,under this conditions L.decastes polysaccharide extraction yield was 26.56%,close to the predicted value 26.62%.Evaluation of the in vitro antioxidant activities of these three polysaccharide fractions from L.decastes indicated all three polysaccharide components showed good2,21-azino-bis(3-ethylbonzothiazoline-6-sulfonicacid?ABTS?radicaland2,2-diphenyl-1-picrylhydrazyl?DPPH?radical scavenging ability and had certain reducing power.Among the antioxidant activity of LDS60 polysaccharide component was higher than that of LDS30 and LDS80 polysaccharide components,and the IC₅₀0 values of ABTS and DPPH radical scavenging capacity were 0.147 mg/mL and 0.299 mg/mL.Comprehensive physical and chemical properties results selected LDS60 components for subsequent separation and purification and structural identification.Crude polysaccharide LDS60 was purified by DEAE-Sepharose Fast Flow and Sephacryl S500 gel column chromatography.After purification,the homogeneous fraction LDS60-A was acquired,which was no nucleic acids and proteins,and has the characteristics of polysaccharide,the average molecular weight was 5.729×10⁶ Da,which belongs to?-configuration neutral polysaccharide.The structure of the LDS60-A component was analyzed by means of acetylation,methylation,gas chromatography-mass spectrometry?GC-MS?,nuclear magnetic resonance?NMR?and scanning electron microscopy?SEM?.The monosaccharide composition,obtained by GC-MS analysis,showed that the LDS60-A was composed of D-glucose,D-galactose and a small amount of L-fucose,L-arabinose and D-xylose and D-mannose in the molar contents of 1.56?1.00?0.28?0.12?0.18?0.28.NMR and methylation analysis results obtained LDS60-A major component of the main chain of?-?1?6?-D-glucopyranose.SEM showed LDS60-A rough surface,mainly in the form of flake or clastic accumulationa,and the intermolecular force was weak.