Isolation,purification,structural Analysis And Biological Activity Of Polysaccharides From Auricularia Auricular

Auricularia auricular is a medicine and food fungus which has rich nutrition.It contains protein,fat,polysaccharide,calcium,phosphorus,iron chemical element and so on.Main function components of Auricularia auricular are polysaccharides which have abundant biological activities.Therefore,it draws more attention to people in the production and scientific research.There are three parts in the study,including optimization of hot water extraction and alcohol precipitation technologies of Auricularia auricular polysaccharides（AAP）investigation of antimicrobial and antioxidant activities of crude AAP,purification and structure elucidation ofAAP.An optimum extraction conditions was obtain by the orthogonal experiment design:extraction temperature 90℃,extraction time 4h,extraction times four,and liquid-solid ratio 70.The significant of each factors was in a following sequenc:liquid-solid ratio,extraction time,extraction times and extraction temperature.Accordingly,the best yield of crude polysaccharides was 6.89%,which was better than previous reports.Antibacterial activities of AAP80 obtained by hot water extraction condition and 80%alcohol precipitation were investigated.Results indicated that crude AAP80 had great antimicrobial activities against Escherichia coli and Staphylococcus aureus.The inhibitory diameters of antimicrobial zones for S.aureus and E.coli are 9.84±0.076 and 5.55±0.182 mm,respectively.But no activities on the others,including Bacillus subtilis,Micrococcus luteus,Saccharomyces cerevisiae and Aspergillus niger.The MIC of AAP against E.coli and s.aureus were 12.5 and 6.25 mg/mL,respectively.AAP showed great inhibitory on S.aureus at pH 5.5-9 and it had a better heat-stability which could stay at 121 C for 15 min with antimicrobial activity.Antioxidant activity of AAP 80 were evaluated in accordance with scavenging free radicals（ABTS,DPPH,Superoxide and Hydroxyl radicals）,reducing power assays and Fe²⁺ chelating ability assay.AAP showed good antioxidant activities on ABTS radicals,superoxide radicals and Fe²⁺chelating,achieving to 78.01%,81.08%,79.44%,respectively,correlated well as the concentration of AAP increasing.One purified polysaccharides（AAP80-3a）was obtained by deproteinization,DEAE-Sepharose Fast Flow and Sephacryl S-400.AAP80-3a is white powder and was eluted as a single symmetrical narrow peak by HPLC,with an average molecular weight was 1.03×105 Da.UV scanning images at 280 and 260 nm showed that it contains no protein and nucleic acid.AAP80-3a was a purified acidic polysaccharide and mainly composed of D-mannose,D-xylose and D-glucose as the molar ratio of 1:0.22:0.16,analyzed by IR,GC,GC-MS and NMR.Among them,the D-xylose are mainly 1,4-linked units,the D-glucose are mainly 1,2,6-linked units,and the D-mannose are mainly 1,4-linked units with a molar ratio of 1:0.28:0.47.It was demonstrated that the main chain of AAP80-3a polysaccharide was connected byl,4-linked mannose.Most of the Glycosidic bond were a and p configuration.