Isolation and identication of a new antioxidant peptide from casein camelmilk using pepsin and pancreatin

Due to the side effects of synthetic antioxidants, bioactive agents derived from natural sources are of great importance. The purpose of this study was to identify and characterize an antioxidant peptide derived from enzymatic hydrolysis of β-casein in camel milk, using pepsin and pancreatin. Enzymatic hydrolysis of camel milk had accomplished using pepsin and pancreatin. The hydrolysate was fractioned using RP-HPLC and the peptide of interest was identified with MALD-TOF/TOF technique. Antioxidant activity of isolated peptide was measured by the use of radical scavenging DPPH, ABTS, hydroxyl and superoxide and inhibition of linoleic acid oxidation. The results of sequencing showed that a purified peptide, called RQ-8, has the sequence of RGLHPVPQ with molecular weight of 903.41 Da. This peptide inhibited oxidation of linoleic acid and also had scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) (IC50=0.046 mg/ml), 2,2'-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS) (IC50 = 0.085 mg/ml), superoxide (O2·-) (IC50 = 0.156 mg/ml) and hydroxyl (OH ·-) (IC50 = 0.021 mg/ml) radicals. In addition, cellular activity assays showed that the RQ-8 peptide had no toxicity on A549 lung cancer cell line. Results indicated that the peptide RQ-8 isolated from camel milk β-casein protein has a strong antioxidant activity.