Study On Producing And Its Antioxidant Activity Of Bioactive Peptides From The Skin Of Rana Chensinensis

The by-product of Rana Chensinensis—the skin, which is rich in protein,trace element and vitamin, also is a source of bioactive peptide. The research use skin of Rana Chensinensis as main material and trypsinase,papain and the complex enzyme including 1:1 trypsinase and papain as proteolytic enzyme, to study the effects of solid-liquid ratio, enzyme dose, pH, condition of temperature and time on DH, and optimize the condition of proteolysis of each enzyme. Various peptides existed in the hydrolysates were fractionated by gel filter chromatography methods. By in vitro antioxidant test, discussed the antioxidant activity of peptides from skin of Rana Chensinensis.Our results laid a theoretical foundation for the development and utilization of antioxidative peptides from skin of Rana Chensinensi.The research result showed as follows:Result:1. The optimal hydrolysis condition with papain was as follws: solid-liquid ratio 1:4, enzyme dosage 6000U/g,pH 6.5,hydrolysis temperature 45℃,hydrolysis time 4h,the DH is 22.02% under the condition.2. The optimal hydrolysis condition with trypsinase was as follws: solid-liquid ratio 1:8, enzyme dosage 10000U/g, pH 8, hydrolysis temperature 50℃, hydrolysis time 4h, the DH is 18.16% under the condition.3. The optimal hydrolysis condition with complex protease was as follws: solid-liquid ratio 1:4, enzyme dosage 14000U/g, pH 8, hydrolysis temperature 55℃, hydrolysis time 4h, the DH is 22.03% under the condition.4. The effect of complex enzyme and papain is similar, considering the convenient and cost, papain was chosen.5. Various peptides existed in the hydrolysates from skin of Rana Chensinensis were factionated by Sephadex G-25 gel filtration. Four components were obtained, the antioxidative activity of separated peptides were studied, the results indicated that antioxidant activity of fraction PⅡis strongest, it showed that antioxidant peptide mainly exist in fraction PⅡ. Fraction PⅡfractionated by Sephadex G-25 gel filtration through the ultraviolet wavelength scan, the maximum absorption wavelength is 280nm. Peptides contain molecular weight is 60KDa and maybe there also contain molecular weight is lower than 2KDa.6. In these peptides, peptide PⅡhas the strongest inhibitory activity in various density,it can Scavenge DPPH·, followed by·OH, but the ability of scavenging O2-·is weak. The inhibitory rate on DPPH·is 94.23% of PⅡ(1mg/mL), the inhibitory rate on·OH and O2-·of PⅡ(16mg/mL) were 86.79% and 26.315%.