Study On Preparation And Founctional Characterization Of Antioxidant Peptides Extracted From Dairy Goat Placenta

Dairy goat placenta contains a rich source of biological and therapeutic compounds thus contributing to its bioactive functions such as anti-aging,anti-inflammatory analgesic,immune regulation,In addition the number of dairy goat in Shaanxi Province is the highest which has significant comparative advantage and high commercial development value.However,the utilization rate of goat placenta is low or almost not utilized,so there will be a good development prospect and important significance for the comprehensive study of goat placenta and the development of its related products.In the current study,antioxidant peptides were obtained from goat placenta by the combination of ultrafiltration and bio-engineering technology,and then the basic physical and chemical properties were evaluated.At the same time,the impact of parities on the antioxidant activity of goat placenta extract(GPE)was comparatively explored.The GPE was separated and purified by membrane separation technology and chromatographic separation in order to obtain the specific functional compounds.Animal models were used to evaluate their antioxidant activities in vivo so as to provide technical support for its commercial exploitation.The study offered a technical reference for the industrialization of goat placenta which has good application value.The main conclusions are as follows:(1)After freeze-drying,the GPE was soluble in water,showing loose porous sponge-like structure,with light yellow and a heavy smell.The second parity was most prominent on antioxidant activity,dacay rate and WSP content.Compared with the ambient temperature,the decay rate was slower under the condition of 4 oC,there was significant difference among parities under different conditions(P<0.05).The preservation rate of second parity at 4 oC for 9 weeks was the highest of these three parities.(2)The results of antioxidant stability showed that the metal ions could significantly decrease the antioxidant activity in a certain way.The high temperature made the antioxidant activity lost rapidly,when mixed with the glucose,fructose and xylose at 70 °C,the mixture could inhibit the decreasing of scavenging activity.In terms of pH,the GPE antioxidant activity in acid condition could maintain good activity whereas the alkaline enviro nment was more favorable for chelating Fe2+.Compared with spray-drying(SD),the product of freeze-drying(FD)has better properties with good solubility and high preservation rate of biological activity.(3)The results of simulated gastrointestinal digestion test in vitro indicated that the DPPH· scavenging activity had no remarkable changes while the Fe2+ chelating ability was significantly reduced(P<0.05)after the 2 h of gastric digestion.Moreover,the research also demonstrated that when peptides were subjected to pepsin digestion,the lower pH and E/S ratio induced stronger antioxidant activity.During the further 2 h trypsin digestion,the Fe2+ chelating ability was significantly increased compared to undigested co mpounds,the antioxidant activity rebounded,additionaly,greater E/S made stronger antioxidant activity.In addition,we also found that the surface hydrophobicity(H0)exhibited rising trend after gastric digestion but with further trypsin digestion declined which was in accordance with the change of antioxidant activity in the two digestion stages.(4)The animal experiments showed that there was no significant difference in weight gain between model group and the other groups(P>0.05)which indicated that the antioxidant peptides of GPE had no significant effect on the growth,feeding,digestion and metabolism of mice.The high dose group could significantly increase the spleen index(P<0.05)whereas had no effect on the kidney index.Compared with model gro up,the activities of T-SOD,T-AOC and CAT in the serum,heart,liver and brain of mice were significantly increased(P<0.05)with the MDA content decreased significantly(P<0.05).In a word,the GPE was benefit to reduce the damage caused by oxidative stress.(5)With DPPH radical scavenging activity,hydroxyl radical scavenging activity and chelating Fe2+ ability as the evaluate indexes of antioxidant activity,GPE was fractionated by ultrafiltration membrane with different molecular weight(Mr).The results showed that when Mr were 5 K-3 KDa and less than 1 KDa antioxidant activities were stronger.Then they were separated and purified by Sephadex G-25 and the four components of S1-S4 were obtained,among which S1 had the strongest antioxidant activity.Finally,S1 was further purified by Sephadex G-10 to obtain two components of S1-1 and S1-2,S1-2 was superior to the other component which could be systematic researched for the purpose of commercial application.