Isolation and Identification of a Novel Antioxidant Peptide from Fermented Sea Cucumber (<i>Stichopus japonicus</i>) 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.