Abstract:

This study aimed to explore the inhibitory effect and underlying mechanism of Terminalia chebula Retz extract （TCE） on tyrosinase activity. High-performance liquid chromatography （HPLC） was employed to analyze the main components of TCE. Enzyme kinetics, fluorescence spectroscopy, and molecular docking techniques were utilized to investigate the inhibitory effects and mechanisms. TCE demonstrates potent inhibitory activity against both tyrosinase monophenolase and diphenolase, with IC₅₀ values of （30.6±0.6） mg/L and （28.3±0.2） mg/L, respectively. Kinetic analysis suggests a mixed-type inhibition mechanism, with inhibition constants K_I = 232.26 mg/L and K_IS = 927.27 mg/L. Fluorescence spectroscopic analysis shows that the intrinsic fluorescence intensity of tyrosinase decreases in a concentration-dependent manner with increasing concentrations of Terminalia chebula extract. Concurrently, the maximum emission wavelength undergoes a red shift from 332 nm to 341 nm. Further molecular docking simulations indicate that gallic acid, chebulagic acid, and corilagin, the key constituents of the extract, can stably dock into the active site of tyrosinase. Through the formation of hydrogen bonds and ionic bonds with critical amino acid residues, these compounds competitively impede substrate binding. TCE significantly suppresses tyrosinase activity by binding to the enzyme’s active site and modifying its molecular conformation, offering a theoretical foundation for its application in the prevention and treatment of hyperpigmentation disorders.

Key words: Terminalia chebula Retz extract, tyrosinase, kinetics, fluorescence spectroscopy, molecular docking