Antioxidant and anti-blackening dual-function silver carp scale peptides: in vitro studies and molecular mechanism

To assess the feasibility of developing fish scale peptides as melanin inhibitors, peptides were extracted from the scales of silver carp (Hypophthalmichthys molitrix). By performing selenocysteine modification, molecular docking, and in vitro analyses, it was identified SGP-C(Se) as the peptide with the strongest antioxidant activity. Further studies included tyrosinase (TYR) inhibition assays, ultrafast kinetic analysis, and validation experiments using B16 melanoma cells. The results revealed that SGP-C(Se) (2 mM) had a strong antioxidant activity, with ·OH and DPPH· radical scavenging rates reaching 98.20% and 97.66%, respectively, and at the same concentration induced 99.27% tyrosinase inhibition. In molecular dynamics, the SGP-C (Se)-TYR system was stable, and its fluorescence lifetime (τ₁=4.40 ns) was shorter than that of SGP-C (Se) (τ₂=5.54 ns) and TYR (τ₃=8.00 ns). At 0.5 mM, SGP-C(Se) significantly reduced the levels of reactive oxygen species and cAMP in B16 cells, down-regulated the expression of proteins associated with the Wnt/β-catenin, cAMP-CREB, and MAPK signalling pathways, and suppressed the mRNA transcription of MITF, TYR, TRP-1, and TRP-2. These findings highlight the potential of SGP-C(Se) as a melanin inhibitor for biological applications.