Peptides from Dalian Stichopus japonicus: Antioxidant Activity and Melanogenesis Inhibition In Vitro Cell Models and In Vivo Zebrafish Models Guided by Molecular Docking Screening

This article aims to reveal the optimal peptide segment with antioxidant activity from Dalian Stichopus japonicus, investigate its anti-melanogenesis effect, and elucidate its mechanisms of action both in vitro and in vivo. The best antioxidant alcalase hydrolysates, identified by the previous screening of proteases, was isolated by ultrafiltration; it was found that the components with a molecular weight of <= 3 kDa exhibited the best activity. The chemical components were characterized using LC-MS/MS. Through molecular docking, GPIGF was identified as the peptide segment with the best antioxidant and melanogenesis-inhibitory activity. A search in the NCBI database revealed that GPIGF is a newly obtained natural oligopeptide. Further experiments with synthesized GPIGF in vitro showed that it effectively reduces cell apoptosis and damage, and inhibits the expression of melanin-related genes, including tyrosinase (TYR), and associated proteins TRP-1, TRP-2, and MITF. In vivo experiments with the zebrafish model demonstrated that GPIGF significantly inhibits AAPH-induced apoptosis in zebrafish larvae, reduces the production of ROS, and suppresses melanin generation on the skin surface without exhibiting embryotoxicity. This study provides a research foundation for the development of antioxidants from Dalian Stichopus japonicus, which could serve as natural whitening and anti-aging agents, supporting its integrated utilization and development.