Tyrosinase inhibition by p-coumaric acid ethyl ester identified from camellia pollen

A tyrosinase inhibitor was separated from camellia pollen with the aid of solvent fraction, macroporous adsorptive resin chromatography, and high-speed countercurrent chromatography. The inhibitor was identified to be p-coumaric acid ethyl ester (p-CAEE) by nuclear magnetic resonance and mass spectrum. Its inhibitory activity (IC₅₀ = 4.89 μg/ml) was about 10-fold stronger than arbutin (IC₅₀ = 51.54 μg/ml). The p-CAEE inhibited tyrosinase in a noncompetitive model with the K _I and K _m of 1.83 μg/ml and 0.52 mM, respectively. Fluorescence spectroscopy analysis showed the p-CAEE quenched an intrinsic fluorescence tyrosinase. UV-Vis spectroscopy analysis showed the p-CAEE did not interact with copper ions of the enzyme. Docking simulation implied the p-CAEE induced a conformational change in the catalytic region and thus changed binding forces of L-tyrosine. Our findings suggest that p-CAEE plays an important role in inhibiting tyrosinase and provides a reference for developing pharmaceutical, cosmetic, and fruit preservation products using pollen.