Research On Preparation Of Soybean DNA Hydrolysates And Antioxidant Properties

Nucleic acid and nucleotide have a great range of potential utilities and development in foodand medical fields for their antioxidant capabilities. Being a kind of nucleic acid, DNA causesmore and more attention of scholars. Soybean dregs contains1%nucleic acid, so it is a potentialplant nucleic acid resource. The research fields of soybean dregs are mainly focused on theextraction and determination of dietary fiber, protein and polysaccharide, but there was no reportabout DNA extraction and functionality. The research on DNA has great realistic significance inincreasing soybean dregs additional value and exploiting nucleic acid resources. So this paper wasperformed on extraction, purification and enzymolysis of soybean dregs DNA, then analyzed andcompared the differences of antioxidation between DNA and hydrolysates.(1) In the cells lysis process, DNA extraction as the indicator, On the basis of single factorexperiment, the response surface was used to study the optimal conditions of extraction. theoptimum technical parameter was obtained: SDS concentration1.85%, pH6, temperature81℃,time70minutes and liquid-to-solid ratio20:1. Under this condition, DNA extraction rate was0.625%.(2) In the purification process, the deproteinization rate and DNA retention rate as theindicators, the paper analyzed the purification effect about isoionic point, TCA and high saltmethod. The high salt method was chose as the optimal purification method: sodium acetate toDNA solution volume ratio2:3, pH4.8, under this condition, the deproteinization rate was85%,DNA retention rate was83%.(3) In the enzymolysis process, The enzymolysis rate of DNA and·OH scavenging ratewere employed as the index, and DNase I as the enzyme. On the basis of single factor experiments,the orthogonal experiment design L9(34) was used to optimize the hydrolysis conditions. Theresults indicated that the optimal enzymolysis conditions were: temperature42℃, pH7, enzymaticconcentration3000U/g, substrate concentration3%, time3.5hours. Under this condition, theOD260of DNA was1.57,·OH scavenging rate was49.25%.(4) In vitro antioxidant experiments, reducing power, DPPH·scavenging rate, O2-· scavengingrate and·OH scavenging rate as indicators were used to study the antioxidant capacity of DNA andhydrolysates. The results showed that DNA and hydrolysates both had excellent antioxidantcapacity. But under the same concentration, their antioxidant capacities were lower than Vc, and DNA hydrolysates was stronger than DNA. The reducing capacity, DPPH· scavenging rate,O-2· scavenging rate and·OH scavenging rate were2.5times,2.4times,2.1times and2.2timescompared with DNA respectively.(5) In vivo antioxidant experiments, CAT, SOD, GSH-Px activity and MDA content in serum,liver and brain of mice as indicators were used to compare the antioxidant effect of DNA, DNAhydrolysates and Ve. The results showed that DNA, DNA hydrolysates and Ve significantlyincreased the activity of CAT, SOD and GSH-Px, decreased the content of MDA, and theydisplayed a good dose-effect relationship. Under the same concentration, the activity of CAT, SODand GSH-Px in hydrolysates groups increased more quickly than DNA groups, meanwhile thecontent of MDA decreased more quickly than DNA groups, and high dosage groups had nodifference, which illustrated that DNA hydrolysates had better antioxidant ability than DNA. Aswell, there was no significant difference between high dosage groups of DNA hydrolysates and Ve.So DNA and DNA hydrolysates had antioxidant capacities.