Identification of novel antioxidant peptides from snakehead (Channa argus) soup generated during gastrointestinal digestion and insights into the anti-oxidation mechanisms

Abstract

Antioxidant peptides obtained from snakehead (Channa argus) soup (SHS) after simulated gastrointestinal (GI) digestion were separated, identified and characterized. Results showed that the fraction with MW < 3 kDa had the highest antioxidant capacity. Four novel antioxidant peptides were identified after RP-HPLC and UPLC-MS/MS. PGMLGGSPPGLLGGSPP and SDGSNIHFPN had the highest DPPH radical scavenging activity (IC₅₀ = 1.39 mM) and Fe²⁺ chelating ability (IC₅₀ = 4.60 mM), respectively. Structures in silico for IVLPDEGK, PGMLGGSPPGLLGGSPP and SDGSNIHFPN suggest at least one β-turn and/or α-helix, which are associated with antioxidant activity. Moreover, our results showed that these three peptides docked with a recombinant Kelch-like ECH-associated protein 1 (Keap1) with a binding score greater than TX6, a good ligand of Keap1. The cell viability assay also showed significant cytoprotective effects against H₂O₂-induced cellular oxidative damage. This information implies that antioxidant mechanisms of novel SHS peptides occurred via activation of cellular anti-oxidation Keap1-Nrf2 signaling pathway.

Keywords: Antioxidant peptides; Cytoprotective effect; Gastrointestinal digestion; Kelch-like ECH-associated protein 1; Molecular docking; RP-HPLC; Snakehead soup; UPLC-MS/MS.