In vitro Antioxidant Effects of Porphyra haitanensis Peptides on H2O2-Induced Damage in HepG2 Cells

In this study, protein from Porphyra haitanensis was used as raw material to prepare an antioxidant peptide, and its antioxidant activity was evaluated in vitro. A model of H2O2-induced oxidative damage in HepG2 cells was established, and the effects of Porphyra haitanensis hydrolysates (PHHs) on superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were detected. Finally, the structure of PHHs was identified by ESI-MS/MS. The results showed that the 1,1-diphenyl-2-pyridylhydrazine (DPPH)-free radical-scavenging ability of PHHs was the strongest (59.28% at 1.0 mg mL−1) when hydrolyzed with an acidic protease for 4 h. PHHs with different concentrations had protective effects on H2O2-induced damage to HepG2 cells, and the protective effect was enhanced with increasing concentrations. When the level was 400 µg mL−1, the cell survival rate was as high as 88.62%. Moreover, PHHs can significantly reduce oxidative damage to HepG2 cells by H2O2, improve SOD activity, and reduce MDA content. The tetrapeptide Asp-Lys-Ser-Thr, with a molecular weight of 448 Da, was identified as an important fraction of PHHs by high-resolution mass spectrometry.