Study On Physicochemical Properties Of Se-enriched Brown Rice Protein And Antioxidant And Anti-inflammatory Activities Of Its Enzymatic Hydrolysates

The main form of selenium in selenium-enriched brown rice is selenoprotein,which has high biological activity.In this paper,three kinds of selenium-enriched brown rice(selenium-enriched by spraying selenium fertilizer on the foliar surface)were used as raw materials to extract the protein by alkaline,and characterized its physicochemical properties and determined the antioxidant activity of selenium-enriched brown rice protein.Trypsin was selected for enzymolysis,and the antioxidant and anti-inflammatory activities of the hydrolysate were determined by in vitro tests.The results show as follows:1.The selenium content in selenium-enriched brown rice increased significantly compared with ordinary brown rice.Selenium-enriched treatment could increase the crude protein in brown rice,decrease myristic acid content and increase stearic acid content.Compared with ordinary brown rice protein,the content of methionine in selenium-enriched brown rice protein was increased,while cysteine content was decreased significantly.Selenium-rich treatment had no significant effect on the molecular weight and subunit of the protein,but it could increase ?-sheet and unordered content,reduce ?-turns and ?-helix content.The selenium-enriched brown rice protein had strong DPPH free radical,hydroxyl radical scavenging ability and reducing power,which were significantly higher than that of ordinary brown rice protein,showed strong in vitro antioxidant activity.2.The selenium-enriched brown rice protein peptide hydrolyzed by trypsin had higher DPPH and ABTS free radical scavenging activities.The molecular weight of the peptide was mainly distributed in the range of less than 1.0 kDa,and it belongs to a low molecular weight peptide.SSPHs,TSPHs,and MSPHs peptide fractions with different molecular weight ranges(Mw>3.5 kDa,Mw:1.0-3.5 kDa,Mw<1.0 kDa)all showed strong antioxidant activity(DPPH,ABTS,FRAP).Among them,the Mw:1.0-3.5 kDa peptide fraction had higher scavenging ability for DPPH and FRAP than others,while the peptide fraction with MW<1.0 kDa had highest ABTS free radical scavenging ability.3.Peptide fractions(SSPHs-2,TSPHs-2,MSPHs-2)with molecular weight of 1.0-3.5 kDa had highest NO inhibitory activity,and significantly inhibited the secretion of PGE2 in LPS-induced RAW264.7 macrophages,and inhibited the protein and mRNA expressions of iNOS/COX-2.SSPHs-2,TSPHs-2,MSPHs-2 concentration-dependently down-regulated the release and mRNA expression of proinflammatory factors TNF-?,IL-6,and IL-1? in RAW264.7 macrophages induced by LPS.SSPHs-2,TSPHs-2,and MSPHs-2 significantly inhibited the degradation of I?B? and nuclear translocation of p65,and phosphorylation of MAPK signaling pathway proteins(JNK,ERK,p38)in LPS-induced RAW264.7 cells,which mediated the activation of NF-?B and MAPK signaling pathways,thereby exerting their anti-inflammatory activities.LC-MS/MS identified the amino acid sequence of TSPHs-2 fractions as:Ala-Leu-Leu-Leu-Gln-Ala-Val-Gln-Ser-Gln-Tyr-Glu-Glu-Lys(ALLLQAVQSQYEEK),the anti-inflammatory activity of selenium-enriched brown rice protein hydrolysate(1.0-3.5 kDa)was related to selenium content and amino acid sequence.