Preparation Of Rice Antioxidant Peptides And Its Anti-aging Effects

China has abundant rice resources and the rice output accounts for 30% of the world.As the component of tice,rice protein has extremely high nutritional value.Rice active peptides can be prepared by enzymatic hydrolysis of rice protein,thus realizing high-value utilization of rice protein.There were more and more studies on rice antioxidant peptides in recent years,but they mostly focused on preparation,separation and purification of rice peptides.There were few reports on the anti-aging effects and its potential molecular mechanism of rice antioxidant peptides.Therefore,in this research,antioxidant peptides were prepared from rice protein through enzymatic hydrolysis.The antioxidant capacity and anti-aging effects of rice antioxidant peptides were determined by chemical antioxidant method and Drosophila model,and the potential mechanisms were studied.Finally,molecular weight determination,sequence identification and antioxidant analysis of the purified peptide were determined.The main findings are as follows:(1)Optimization of the preparation process on rice antioxidant peptidesTaking antioxidant capacity(ABTS free radical scavenging rate,ORAC value)and degree of hydrolysis as indicators,neutral protease was selected for hydrolysis after screening test.On this basis,through single factor experiment,response surface experiment and BP neural network-genetic algorithm model comparison,the optimized preparation process conditions of rice antioxidant peptide were: reaction temperature50℃,system p H 8.2,material-to-liquid ratio 17.65 g/100 m L,the amount of enzyme added 4374 U/g.(2)Determination of antioxidant capacity in vitro and structural characterization of rice antioxidant peptidesThe results showed that rice antioxidant peptides had strong DPPH,ABTS and hydroxyl free radical scavenging activities,as well as metal ion chelating ability,metal ion reduction ability and anti-lipid peroxidation ability.FTIR,SEM and DSC were conducted to determine the structure of rice protein and peptides.It was found that the microstructure of peptides had changed from a spherical distribution to a porous fragmented distribution,and the content of hydrophobic amino acids had increased during proteolysis process.These might have contributed to the antioxidant activities of rice peptides.(3)Studies on the anti-aging effect of rice antioxidant peptides in Drosophila and its molecular mechanismStudies had shown that rice antioxidant peptides at 0.2% and 3.2% concentrations could significantly prolong the maximum lifespan,50% survival time and average lifespan of fruit flies.Also,rice antioxidant peptides could increase the activity of SOD,Mn-SOD and CAT,reduce MDA content.The survival rate of Drosophila in acute oxidative injury fly model was increased.The results showed that rice antioxidant peptides could increase the expression of Cu Zn-SOD,Mn-SOD,Nrf2 and CAT genes in Drosophila,and decrease the expression of S6 K,TOR,Keap1 and MTH genes,indicating that rice antioxidant peptides could regulate aging process through the antioxidant pathway Nrf2/Keap1,aging-related signaling pathways(TOR,S6K)and the longevity gene MTH.(4)Studies on isolation,identification and structure-activity relationship of rice antioxidant peptidesThe rice antioxidant peptides was separated and purified by Sephadex G-25 to obtain the F2 component with the highest antioxidant activity.MALDI-TOF-MS/MS was used for amino acid sequence identification,and a tetrapeptide SPEH was obtained,which can bind to FKBP12 protein through hydrogen bond,salt bridge and π-πinteractions to form a stable complex.The binding site is FRB site,indicating that SPEH can bind to FKBP12 protein to block the m TOR signaling pathway,which is similar to rapamycin.