Pacific oyster-derived peptides: extraction optimization, structural characterization, and functional evaluation

Oysters are an abundant marine protein resource with strong potential for generating bioactive peptides. In this study, an integrated strategy combining ultrasound pretreatment with response surface methodology–optimized enzymatic hydrolysis was developed to efficiently produce functional peptides from Crassostrea gigas . Ultrasound-assisted hydrolysis markedly improved peptide yield and promoted the formation of low-molecular-weight peptides, with fractions < 3 kDa accounting for 83.7% of the hydrolysate. Structural characterization revealed that the resulting peptides were enriched in hydrophobic and aromatic amino acids and exhibited increased conformational flexibility with reduced ordered secondary structures. Functionally, oyster peptides demonstrated strong in vitro antioxidant activity, including effective radical scavenging and ferric-reducing capacity. In cellular models, the peptides significantly alleviated hydrogen peroxide (H₂O₂)-induced oxidative stress in HepG2 cells by reducing intracellular reactive oxygen species (ROS), enhancing endogenous antioxidant enzyme activities, and suppressing lipid peroxidation. Furthermore, in differentiated C2C12 myoblasts, the peptides improved cellular energy metabolism under oxidative challenge, as evidenced by increased ATP levels and reduced LDH release, indicating promising anti-fatigue potential. Collectively, the resulting peptides reduced ROS accumulation in HepG2 cells and increased ATP levels in C2C12 myotubes, supporting their potential as antioxidant and cellular energy metabolism-supporting ingredients.