Identification of Two Novel Antioxidant Peptides from Camel Milk Using Digestive Proteases: Impact on Expression Gene of Superoxide Dismutase (SOD) in Hepatocellular Carcinoma Cell Line

Camel milk has high levels of antioxidant peptides; therefore has a significant role in nutrition and health. There is a wide range of diseases associated with oxidative stress in the body, thereby preventing the production of free radicals followed the occurrence of such reactions have an important role in human health. Some peptides derived from natural sources as natural antioxidants have a significant role in the inhibition of free radicals. The aim of this study was the identification and purification of camel milk proteins and evaluation of their antioxidant properties. For this purpose, camel milk proteins were hydrolyzed and examined the antioxidant properties of resulting peptides. Ultrafiltration and reverse-phase HPLC techniques were used for fractionation of the hydrolysate. Antioxidant activity of peptides were evaluated using different methods such as 2,2′-diphenyl-1-picrylhydrazyl (DPPH^·), 2,2′-azinobis(3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS⁺), superoxide (O2^·?), hydroxyl (OH^·?) and polyunsaturated fatty acid peroxidation assays. The real-time PCR was performed to evaluate changes in expression of superoxide dismutase gene (SOD) as an antioxidant enzyme in HepG2 cells treated with different concentrations of peptide. Active peaks were analyzed using tandem mass spectrometry and thus identified two peptides NEDNHPGALGEPV (NV-13) and KVLPVPQQMVPYPRQ (KQ-15) with 1348.38 and 1780.15 dalton molecular weight, respectively. Both peptides showed antioxidant effects but KQ-15 peptide showed stronger effects than other. Molecular analysis showed that KQ-15 peptide was also able to increase the expression of SOD gene. The results show that the NV-13 and KQ-15 peptides have a high antioxidant capacity and they can be used to deal with diseases associated with oxidative stress.