Preparation And Antioxidant Activity Analysis Of Protein And Enzymolysis Polypeptide From Edible Fungi

Edible fungi have good flavor and are rich in protein content.However,studies on functional components of edible fungi are mainly focused on polysaccharides instead of proteins.If more studies on the activity of edible fungi proteins could be conducted,we can effectively strengthen the development of edible fungi protein resources and enhance their comprehensive utilization.In this study,seven edible fungi including Pleurotus geesteranus,yellow Flammulina velutipes,Pleurotus eryngil,Pleurotus citrinopileatus,Pleurotus rhodophyllus,Pleurotus ostreatus and Cordyceps flower were used as raw materials to measure their main nutrient components.Alkali extraction-acid precipitation and enzymatic hydrolysis were employed to obtain proteins and corresponding polypeptides respectively.The antioxidant capacity of different proteins and polypeptides by enzyme digestion were preliminarily evaluated by three in vitro antioxidant activity evaluation methods including DPPH,reducing power and ORAC.The most powerful antioxidant polypeptide was used to perform further purification by macroporous resins,the adsorption kinetics and thermodynamics of macroporous resins were studied.The protective effect of different isolated fractions on oxidatively damaged PC12 cells was studied.The detailed results are as follows:?1?From the results of the main nutrients contents,the protein content was from 14.87%to31.52%;the fat content of seven edible fungi was from 0.86%to 6.88%;the ash content was from 3.54%to 6.38%;the moisture content was from 5.05%to 9.94%;and the total sugar content was from 27.57%to 52.06%.Among them,Cordyceps flower had the highest fat and protein content,and Pleurotus geesteranus had the highest ash content.The highest moisturer and total sugar contents were from Pleurotus citrinopileatus and Pleurotus eryngil respectively.?2?The antioxidant activities of seven edible fungi were evaluated by three in vitro antioxidant activity evaluation assays.Cordyceps flower was the most effective one when testing with the DPPH free radical scavenging assay at the concentration of 1 mg/mL.The clearance rates of its proteins and polypeptides were 93.77%and 90.83%respectively,which were a little bit lower than that of GSH?96.12%?at the same concentration.The strongest reducing power among different edible fungi at the same concentration was from yellow Flammulina velutipes.The reducing power of its proteins and polypeptides were 0.67 and 0.66 respectively,which were lower than that of GSH?0.72?at the same concentration.In the ORAC activity assay,yellow Flammulina velutipes proteins had the highest ORAC value?2974.33?mol TE/g?,and Pleurotus geesteranus polypeptides?PGP?had the highest ORAC value?7541.09?mol TE/g?.They were all higher than the ORAC value of GSH?1613.60?mol TE/g?.?3?The adsorption kinetics and thermodynamics of four macroporous resins including SP-825L,XAD-16,HP-20 and HP-2MGL towards Pleurotus geesteranus polypeptides were studied.The results revealed that the pseudo-first-order kinetic equation can fit the XAD-16 resin well.The pseudo-second-order kinetic equation can fit the HP-20 and HP-2MGL resins well.In contrast,the intragranular diffusion equation can better fit the SP-825L and XAD-16 resins.The Freundlich model is suitable for describing the isothermal adsorption behavior of the resin on Pleurotus geesteranus polypeptides,and the adsorption of the resin on Pleurotus geesteranus polypeptides is an exothermic physical adsorption process.We finally selected XAD-16macroporous resin for separation and enrichment of Pleurotus geesteranus polypeptides.Different separation components by this resin were further evaluated for their protective effect on H₂O₂-induced oxidatively damaged PC12 cells.The results showed that component PGP-IV?60%ethanol elution components?had the best protective effect.