Structure,Selenium Existing Form And Hepatoprotective Effect Of Se-enriched Corn Peptides In The Paracetamol–induced Liver Injury

In order to further explore the function and characteristics of Se-enriched corn peptides,and promote its utilization for practical production,in this paper,Se-enriched corns were planted by spraying selenium fertilizer on the foliage.The corn proteins were extracted by Na OH and alcohol solutions,and then were hydrolyzed by Alcalase.The Se-enriched corn peptides were fractionated by ultrafiltration membrane and the Se content was determined by HG-AFS.The distribution of Se in each molecular weight fraction of Se-enriched corn peptides was analyzed.The existing form of Se in Se-enriched corn proteins and peptides were analyzed by HPLC-AFS.The effects of Se-enriched corn peptides on the metabolic related enzymes of paracetamol were investigated through establishing the model of paracetamol-induced mice liver injury.The hepatoprotective effect of Se-enriched corn peptides was evaluated and its possible mechanism was discussed.The primary structure of Se-enriched corn peptides was identified by HPLC-ESI-MS/MS method coupled with mass spectrometry database.And the potential physiological activity was analyzed according to the primary structure.The major results are as follows:1.Existing forms of Se in the Se-enriched corn proteins and peptidesThe contents of Se in grains,proteins and peptides of Se-enriched corn were2.19mg/kg,12.97mg/kg and 32.37mg/kg,respectively.After fractionated according the molecular weight of the Se-enriched corn peptides,the Se content of each fraction was detected.The results showed that Se evenly distributed in the peptides.74.8% corn peptides' molecular weight was within 1-5k Da,which contained 68.37% Se.The Se existing form in Se-enriched corn proteins was extracted by HCl digestion and enzymatic hydrolysis,and Se Cys and Se Met were detected in the Se-enriched corn proteins by HPLC-AFS.In addition,the inorganic Se in Se-enriched corn proteins and peptides was not detected.So,we speculate that most of the Se in the Se-enriched corn proteins and peptides were existing in the form of organic selenium,including Se Cys and Se Met.2.Protective effect of Se-enriched corn peptides on liver injury induced by paracetamol in miceIn order to investigate the protective effect of Se-enriched corn peptides on drug-induced liver injury,the model of paracetamol-induced mice liver injury was established.The results showed that Se-enriched corn peptides could restrain paracetamol metabolism through reducing the activities of UGT(UDP-glucumno-syltransferase)and SULT(sulfotransferase)(P<0.05);and reduce the production of toxic substances by inhibiting the activities of cytochrome P450-2E1 and cytochrome P450-1A2 in mice liver(P<0.05);and enhance the abilities of discharging toxic metabolites and resisting oxidative stress by increasing the activities of GST(glutathione S-transferase)and GSH-Px(glutathione peroxidase)and reducing the depletion of GSH(glutathione)(P<0.05).In summary,Se-enriched corn peptides were effective in protecting the liver against paracetamol by three factors,and Se had a synergistic effect on the liver protection of corn peptides.3.Structure identification of Se-enriched corn peptidesThe primary structure of Se-enriched corn peptides was identified by HPLC-ESI-MS/MS coupled with mass spectrometry database,and 8 Se-peptides and 29 corn peptides were identified.Se-peptides were Phe-Se Cys,Trp-Se Met-Gln-Glu,Trp-Se Met-Lys-Glu,Se Cys-Tyr-Glu,Phe-Se Me Cys-Met,Se Cys-Cys-Ala-Se Me Cys,Phe-Se Me Cys-Val-Gln and Phe-Se Me Cys-Val-Lys,respectively.The results showed that Se in Se-enriched corn peptides was present in Se Cys,Se Met and Se Me Cys,and there are high contents of hydrophobic amino acids such as Trp,Met,Val,Ala and Phe.Similarly,in the corn peptides,the content of hydrophobic amino acid is also high,of which seven peptides contain branched-chain amino acids Val,Ile or Leu.In addition,Ala and Leu can facilitate alcohol metabolism.We considered that the organic Se and hydrophobic short peptides in Se-enriched corn peptides have an important contribution to the hepatoprotective effect.