Optimized Active Fractions And Biological Evaluation Of Soybean Antioxidant Peptides

This study was granted by Key Projects in the National Science&TechnologyPillar Program during the Twelfth Five-Year Plan Period (2012BAD33B03) andfocused on the optimizing fraction and biological evaluation of antioxidant peptidesfrom soybean. The results were as follows:(1) The optimized key technology of controlled enzymatic hydrolysis of soybeanantioxidant hydrolysateds (SAH) from was studied. The soybean protein powder (SPP)(protein content of43.94%) was hydrolyzed by Alcalase Food grade (FG)2.4L.Hydrolysis degree and DPPH radical scavenging were used as evaluation index. Theeffect of temperature, pH value and ratio of enzyme/soybean protein powder onDPPH radical scavenging and DH of SAH were studied using one-factor-at-a-time(OFAT) experiment. Based on the results of OFAT, response surface methodology(RSM) was used to construct a quadric equation. Partial derivatives was calculatedand the optimal hydrolysis parameters of strongest antioxidant capacity of peptideswere obtained at: temperature of50oC, pH value of10.32, and ratio ofenzyme/soybean protein powder of12%. Under this conditions, the DPPHscavenging ability was67.16±2.95%and hydrolysis degree was35.00±1.08%。(2) The optimized active fractions and biological evaluation soybean antioxidantpeptides (SAP) were studied. The SAH were separated by the ultrafiltrationmembranes of1kDa、3kDa、10kDa and30kDa to obtain the SAP. The results ofmid-infrared spectroscopy (MIR) showed the SAP-2to5fractions had α-helix、β-folding and non-periodic conformation except SAH. Based on the results of in vivoand in vitro, the SAP-4showed the highest antioxidant ability. The result of biologicalevaluation showed the no toxic effect of SAP-4on mice was obtained. The amino acidof SAP-4was67.85g per100g and8kinds of essential amino acid were obtained.(3) The optimized fractions and structure identification of high active soybean antioxidant peptides were studied. The SAP-4was purified by size exclusionchromatography (SEC) to obtain6elution peaks. Then the peaks were determined theDPPH radical scavenging activity. The SAP-4-III had the highest DPPH radicalscavenging activity. Then LC-MS/MS Q Trap and results of amino acid were used toobtain amion acid sequence FHDHE. This synthetic peptide was98.82%purity andthe DPPH radical scavenging activity was22.64±1.02%。(4) The improvement Improvement of antioxidant activity of peptides by PEFtechnology was studied. The SAP-3was treated by pulsed electric field (PEF) toimprove antioxidant activity. DPPH radical scavenging (%) was used to evaluate theantioxidant activity. The effect of electric field intensity and pulsed frequencey onDPPH radical scavenging of SAP-3were studied using OFAT experiment. Based onthe results of OFAT, RSM was used to construct a quadric equation. Partial derivativeswas calculated and the optimal conditions were as follows: concentration of10mg/mL, electric field intensity of14.37kV/cm and frequency of2000Hz. Underthese conditions, the antioxidant activity of was85.00%.