Inhibition effects and binding behavior of alginate oligosaccharides on tyrosinase and elastase: multi-spectroscopic approaches and zebrafish evaluation.

Alginate oligosaccharides (AOSs) are natural marine oligosaccharides with diverse physiological functions, which have broad application prospects in both the cosmeceutical and food industries. This study systematically investigated the inhibitory mechanisms of AOSs against tyrosinase and elastase, two key enzymes associated with skin aging, by combining multi-spectroscopic approaches with zebrafish in vivo evaluation. Results demonstrated that AOSs acted as a reversible mixed-type inhibitor for both enzymes, exhibiting moderate inhibitory activities with IC50 values of 7.37 ± 0.15 mM for tyrosinase and 10.05 ± 0.17 mM for elastase. Fluorescence quenching assays revealed that AOSs interacted with the two enzymes through a static quenching mechanism. Further investigations via synchronous fluorescence and ANS-binding assay confirmed that AOS binding induced conformational rearrangements of both enzymes, altered the microenvironments around tyrosine and tryptophan residues, and decreased their surface hydrophobicity. CD spectra results indicated that AOSs could cause changes in the secondary structures of the two enzymes, which was closely related to the loss of enzymatic activity. Zebrafish experiments further verified that AOSs could effectively inhibit melanin formation and alleviate oxidative stress in vivo. Collectively, these findings provide a comprehensive mechanistic basis for the dual skin-whitening and anti-wrinkle efficacy of AOSs as a multifunctional active ingredient in cosmeceutical formulations.