Effect Of Frying On Antioxidant Activity And Antiproliferation Activity Of Protein-phenolic Complex From Barley Malt

Proteins are the main nutritional components of barley,and polyphenols are the important functional components in barley.During the producting process,both of them may affect and interact with each other,resulting in non-covalent or covalent bonding or fragmentation,which ultimately leads to changes in nutrition and function of barley.In this work,the protein-polyphenol complex and phenolic-reduced protein were extracted from raw malt,fried malt and black malt with frying at different degrees and investigated the effects of the frying on their phytochemical profiles,antioxidant capacity,cytotoxicities and antiproliferative activities.The main researches and conclusions are as follows:1.The raw malt,fried malt and black malt are extracted different kinds of proteins by Osborne method.It was found that different degrees of thermal processing had different effects on soluble protein contents and total phenolic contents of different kinds of proteins.The soluble protein content from high to low was raw malt(134.31±11.31 mg/g)> fried malt(105.72±8.36 mg/g)> black malt(71.07±1.24 mg/g).Its content gradually decreased with the degree of frying and was the same as its total phenolic contents which from high to low showed as raw malt(27.13±0.87 mg GAE/g)> fried malt(15.50±0.45 mg GAE/g)> char malt(11.33±0.28 mg GAE/g).While the trend of alkaline soluble protein,salt soluble protein and gliadin were opposite to that of water soluble protein.Comparing with the phenolic non-reduced group,soluble protein content in the phenolics reduced group all were increased,indicating that there was the interaction between free phenolics and protein,resulting in the decrease of protein solubility.By SDS-PAGE,it further confirmed that water soluble protein of raw malt could covalently bind to phenolics.2.It was found that frying had different effects on the antioxidant activity of different kinds of malts proteins by studying three kinds of vitro antioxidant experiments including ABTS method,FRAP method and ORAC method.The ABTS radical scavenging ability of water soluble protein from strong to weak was raw malt(76.07±0.33%)> Fried malt(59.96±0.79%)> black malt(34.94±1.78%).Its iron ion reducing ability from strong to weak was raw malt(0.35±0.014 m M)> fried malt(0.26±0.034 m M)> black malt(0.23±0.051 m M).And its oxygen radical scavenging ability from strong to weak was raw malt(6.08±0.95 μmol TE/g FW)> fried malt(3.77±0.25 μmol TE/g FW)> black malt(1.90±0.061 μmol TE/g FW).They indicate that frying would reduce the antioxidant activity of water soluble proteins.While the antioxidant capacity of alkali soluble protein,salt soluble protein and gliadin were opposite to that of water soluble protein which increased with the deepening of frying.The interaction between water soluble protein and phenolics would reduce its antioxidant activities.While the abilities of gliadin to scavenge ABTS radicals was not greatly affected by phenolics,which could be mainly related to protein structure and its composition of amino acids.3.Cytotoxicities and antiproliferative activities of four kinds of proteins from raw malt,fried malt and dark malt toward Caco-2,Hep G2 and He La were studied,and the results showed that: Water soluble proteins from raw malt and fried malt had antiproliferative activities on He La.Salt soluble protein from raw malt showed anti-tumor effects on Caco-2 and Hep G2.Gliadins from three kinds of malts showed antiproliferative activities on Hep G2 and He La.And the inhibition was strengthened with the increase of the degree of frying.Alkali soluble proteins from three kinds of malts had anticancer activities on He La,but as the degree of frying was deepened,the activities were weakened.In particular,it was worth mentioning that the antiproliferative activity of phenolic non-reduced group was better than that of phenolic reduced group,indicating that phenolics could improve the anticancer activities of proteins from malts.