Discovery of a novel dual-functional peptide from oyster protein hydrolysates with antioxidant and osteogenic properties: <i>in vitro</i> , <i>in silico</i> , and zebrafish model evaluation

Bioactive peptides are emerging as promising agents for promoting osteogenesis and alleviating oxidative stress - both critical factors in osteoporosis development. In this study, we aimed to discover peptides from oyster protein hydrolysates with dual antioxidant and osteogenic activities. Hydrolysates were prepared from oyster mantle, non-mantle, and whole-body tissues, among which the <1 kDa fraction of the mantle hydrolysate showed the highest bioactivity. Peptides in this fraction were identified by LC-MS/MS and screened <i>via in silico</i> bioactivity prediction and molecular docking with BMPR1A, a key receptor in the BMP osteogenic signaling pathway. Three candidate peptides, FFEPKF (FF6), PFRFTGF (PF7), and APFRFTGF (AP8), were synthesized and evaluated for their antioxidant activity in an H₂O₂-induced oxidative stress model using MC3T3-E1 cells. Among them, FF6 exhibited the most pronounced effect, significantly reducing intracellular ROS levels, restoring mitochondrial function, and promoting osteogenic differentiation. Furthermore, FF6 supplementation mitigated bone loss and upregulated osteogenic gene expression (<i>Runx2</i>, <i>Osx</i>, <i>Col1a1</i>, and <i>Sox9a</i>) in a dexamethasone-induced zebrafish model. These findings suggest that FF6 is a promising candidate for development into functional foods or nutraceuticals aimed at preventing oxidative stress-related bone disorders.