Synthesis and biological activity of hydroxybenzylidenyl pyrrolidine-2,5-dione derivatives as new potent inhibitors of tyrosinase

Abstract

In this study, we describe the synthesis and tyrosinase inhibitory activity of a new family of hydroxybenzylidenyl pyrrolidine-2,5-dione compounds. Among them, compound 3f (HMP) exhibited the highest inhibition, 83.87%, at a concentration of 20 μM, on the L-DOPA oxidase activity of mushroom tyrosinase. We also predicted the tertiary structure of tyrosinase, simulated its docking with HMP and confirmed that HMP strongly interacts with tyrosinase residues. This result suggested that the binding activity of HMP with tyrosinase could be high. Based on these results, we determined the IC₅₀ value for HMP inhibition of mushroom tyrosinase activity. HMP inhibited mushroom tyrosinase with an IC₅₀ value of 2.23 ± 0.44 μM, which is more potent than the anti-tyrosinase activity of kojic acid (IC₅₀ = 20.99 ± 1.80 μM), a well-known tyrosinase inhibitor. Kinetic analysis of tyrosinase inhibition revealed that HMP is a competitive inhibitor (K_i = 4.24 × 10⁻⁷ M at 1.25 μM and K_i = 1.82 × 10⁻⁶ M at 20 μM). HMP also inhibited melanin production and tyrosinase activity in B16F10 melanoma cells (B16 cells). These data strongly suggest that HMP can suppress the production of melaninvia the modulation of tyrosinase activity.