Isolation and Identification of a Novel Antioxidant Peptide from Fermented Sea Cucumber (Stichopus japonicus) Intestine and Its Protective Effects on HepG2 Cells from Oxidative Damage

The development of antioxidant peptides that can benefit both human health and the environment is a major focus in antioxidant research. The study aimed to isolate and identify antioxidant peptides from fermented sea cucumber intestines and evaluate their cytoprotective effects against H2O2-induced oxidative damage in HepG2 cells. A new peptide AAAFEGKW (AP3) was obtained through liquid chromatography-tandem mass spectrometry and virtual molecular docking screening. Synthetic peptide AP3 (1000 μmol/L) demonstrated significant antioxidant activity, with 1,1-diphenyl-2-picrylhydrazyl, superoxide anion, and hydroxyl radical scavenging capacities of 52.99 ± 1.05, 65.10 ± 0.70, and 54.17 ± 0.85%, respectively. Cytoprotective analysis revealed that the peptide AP3 protected oxidatively damaged HepG2 cells by activating the Keap1/Nrf2 pathway, enhancing the activities of endogenous antioxidant enzymes, and reducing the levels of reactive oxygen species and malondialdehyde. Thus, AP3 exhibits strong potential as a novel antioxidant, making it suitable for applications in functional foods and food preservation.