Anti-photoaging activity of cod peptides: structural characterisation and clinical validation

The role of collagen peptides in anti-photoaging has attracted considerable research attention; however, the structure-activity relationship between their specific structural characteristics and biological efficacy remains poorly defined. In this study, collagen peptides from five sources, cod skin (CP), tilapia skin (TP), cowhide (BP), pig skin (PP), and chicken bone (JP), were selected to systematically compare their anti-photoaging activities in a UVA-induced L929 cell model and to investigate the mechanisms underlying their effects through analysis of molecular weight distributions, amino acid compositions, and sequence features. The results showed that CP, TP, and BP had stronger activities in increasing cell viability, enhancing the expression of TGF-β1, COL1, and HAS-1/2/3, and inhibiting ROS generation and over-activation of MMP-1/3 in UVA-damaged cells, with CP having the most significant effect. Mass spectrometry analysis showed that CP, together with TP and BP, shared the characteristics of N-terminal regions enriched in hydrophobic residues and C-terminal regions rich in hydrophobic and basic amino acids; in addition, CP presented a higher proportion of N-terminal electronically characterized amino acids and aromatic amino acids, potentially contributing to its superior antioxidant capacity and collagen metabolism regulation ability. Further double-blind placebo-controlled clinical trials confirmed that continuous oral administration of CP for 8 weeks significantly improved skin hydration, elasticity, and wrinkle reduction. Collectively, CP emerged as the most promising anti-photoaging candidate among the five collagen peptides, and its structure-function characteristics and clinical efficacy provide a robust foundation for its application and development in the field of functional foods.