Inhibitory mechanism of esculetin on tyrosinase and browning of fresh-cut apple: New perspectives

The anti-tyrosinase mechanism of esculetin has been systematically investigated by various spectroscopic techniques and molecular simulation. And the outcomes confirmed that esculetin was a competitive and excellent tyrosinase inhibitor (IC50=43 ± 0.5 µmol L−1). The binding of esculetin to tyrosinase affected the hydrophobic microenvironment of the enzyme and altered its conformation. Thermodynamic analysis and molecular docking demonstrated that the binding was driven by hydrophobic interaction and hydrogen bonding. Circular dichroism and molecular dynamic analysis revealed that esculetin induced the structural stretching of tyrosinase and slightly impacted the microenvironment of amino acid residues. Cell assays further demonstrated that esculetin inhibited intracellular tyrosinase activity and melanin production but showed no significant effect on cell proliferation. Additionally, studies on browning inhibition indicated that esculetin delayed the browning of fresh-cut apples by suppressing phenolic metabolism, strengthening antioxidant systems, and reducing membrane-lipid peroxidation. The above discoveries offered new viewpoints for understanding the suppressive mechanism of esculetin on tyrosinase and browning, as well as scientific evidence for its potential application in food preservation and medicine.