Methyl lucidenate F isolated from the ethanol-soluble-acidic components of Ganoderma lucidum is a novel tyrosinase inhibitor

Tyrosinase is a key enzyme in the biosynthesis of melanin, and the use of inhibitors against tyrosinase can prevent hyperpigmentation by inhibiting enzymatic oxidation. However, the current use of tyrosine inhibitors is limited by their low activities and high toxicities. The aim of the present research was to develop novel whitening agents, or tyrosinase-targeted medicine, from a submerged culture of the fungus Ganoderma lucidum. Methyl lucidenate F was isolated from the ethanol-soluble-acidic components (ESACs) of G. lucidum, with the structure of ESACs elucidated via UV, LC-MS, and ∨13C-NMR spectral analysis. The tyrosinase inhibitory activity was measured using catechol as a substrate. Methyl lucidenate F displayed uncompetitive inhibition of the potato tyrosinase activity, for which Lineweaver-Burk plots revealed a maximum reaction rate (V∧max) of 0.4367/min, Michaelis constant (K∧m) of 6.765 mM and uncompetitive inhibition constant (K∧i) of 19.22 μM. Meanwhile, methyl lucidenate F (tetra cyclic triterpenoid) exhibited high tyrosinase inhibitory activity, with an IC∧50 of 32.23 μM. These results suggest that methyl lucidenate F may serve as a potential candidate for skin-whitening agents.