Studies On The Isolation, Purification And Bioactivity Of Antioxidative Peptides From Sesame Protein

Sesame contains a large number of oils, fats and protein. Sesame mainly is used to extract oil at present, while the availability of sesame protein is restrained. It is significant to research and develop sesame protein more. Enzyme hydrolysis process of sesame protein, separation, purification and bioactivity of sesame anti-oxidative peptides was studied in this article. Conclusions can be summarized as follows:(1) The anti-oxidizablity of hydrolyzed sesame protein by papain was the strongest as compared with trypsin, pepsin, AS1398 dispase and Alcalase alkaline proteinase. So papain was selected to the special enzyme used to prepare functional peptide of sesame protein.(2) The heat treating before enzymolysis was beneficial to the enzymatic hydrolysis. The optimum technological operation was to heat the protein solution for 10 minutes at 90℃.(3) The optimum hydrolytic processing parameters of sesame protein by papain were concluded as follows: substrate content 9.0 g/L, papain content 20.0%, pH6.5, temperature 50℃, reaction time 6 hours. Under this condition the anti-oxidizablity of zymolyte was the strongest and the inhibition ratio to pyrogallol autooxidation is 35.6%. Compared with others factors, temperature, pH, enzyme content were the most three important influencing factors of hydrolytic process.(4) Four components could be got when the sesame protein zymolyte was separated by Sephadex-G25 gel chromatographic column. The molecular weight distributions were 17090 - 5593 Da, 5593 - 3207 Da, 3207 - 1571 Da, < 1571 Da.(5) The desalting effect of zwitterion exchange resin was similar to that of mixed-bed, and there was no obvious difference between them. But the yield of hydrolyzed peptides differed palpably between the two methods. The yield of the former method was only 68.8%, and the latter usually excelled the former. The yield was reached the top to 81.5% when the proportion of negative to positive ion exchange resin was 1.5 to 1.(6) Three components could be got when the componentâ…¢of the strongest bioactivity was separated by strong-acid positive ion exchange chromatographic column. Then component III-2 and III-3 of stronger bioactivity were separated by strong alkaline negative ion exchange chromatographic column into two and three components respectively. To get purer peptide, further isolation was needed because componentâ…¢-2-a andâ…¢-3-b were mixed peptides.(7) It was concluded by non-oil system out-of-body activity tests that the total reducing power, the scavenging power on·OH and O₂^-·of hydrolyzed sesame protein by papain were not as good as BHT and Vitamin C on the same concentration level. The higher the concentration was, the stronger those three kinds of power became. The IC₅₀ of scavenging power on·OH and O₂^-·of hydrolyzed sesame protein by papain were 786.1±11.5 mg/L and 27.5±2.1 mg/L respectively. Sesame protein was, as it were, a raw material used to produce anti-oxidative peptides.(8) The results were obtained by oil system in-body activity tests that the hydrolyzed sesame protein by papain could effectively inhibit the oxidation of lard oil, linoleic acid and PUFA in lipovitellin induced by Fe²⁺. To some extent the oxidation-inductive cycle of linoleic acid system added in different amount zymolyte became longer. In lipovitellin system, the anti-oxidation effectiveness of zymolyte was similar to that of Vitamin C. The IC₅₀ of Vitamin C and zymolyte were 39.1±2.1 mg/L and 36.3±1.8 mg/L respectively.(9) The difference contrast wasn't noTab in the body and some organs by comparing the body weight and some organs' appearance and weight of mice fed with normal feedstuff, low, middle and high dose levels respectively. It was preliminarily judged that the zymolyte of sesame protein was safe and edible.(10) It was concluded that the zymolyte of sesame protein could effectively reduce the amount of MDA in serum, liver and encephalon by comparing the mice groups fed with normal feedstuff, low, middle and high dose levels respectively, especially the high dose level group. The activity of GSH-PX and SOD in serum, livers and encephalon was heightened compared to that of the normal group. There were obvious differences between middle, high dose levels groups and normal group. The activity of CAT in livers of middle, high dose levels groups was obviously different with that of normal group. It proved that the zymolyte of sesame protein was a kind of good functional peptides mixture.