Antioxidant Peptide Purified from Enzymatic Hydrolysates of Isochrysis Zhanjiangensis and Its Protective Effect against Ethanol Induced Oxidative Stress of HepG2 Cells

Marine microalgae have been widely applied in cosmaceuticals, nutraceuticals, and functional foods. In the present study, we first investigated the hepatoprotective effects of peptide purified from microalgae, Isochrysis zhanjiangensis on HepG2 cells alcoholic injury. I. zhanjiangensis was hydrolyzed utilizing chymotrypsin, trypsin, pepsin, and by vitro gastrointestinal digestion. Among hydrolysates, the gastrointestinal hydrolysate showed relatively high free radical scavenging ability preliminarily and was purified with following sequential chromatography methods. The amino acid sequence and molecular mass of the purified peptide from I. zhanjiangensis (PIZ) was identified as Asn-Asp-Ala-Glu-Tyr-Gly-Ile-Cys-Gly-Phe (NDAEYGICGF; MW, 1088.16 Da) via Q-TOF ESI/MS. Additionally, PIZ attenuated ethanol-induced cytotoxicity and inhibited the production of intracellular reactive oxygen species by DCFH-DA assay. Western blot results showed that superoxide dismutase (SOD) and glutathione (GSH) levels up-regulated with PIZ treatment before alcohol exposure while gamma-glutamyltransferase (GGT) protein expression down-regulated. These results provide an opportunity to discover new highly active peptide against alcohol toxicity in HepG2 cells.