Design, synthesis, and biological evaluation of symmetrical azine derivatives as novel tyrosinase inhibitors

Abstract

A series of symmetrical azine derivatives containing different substituted benzyl moieties were designed, synthesized, and evaluated for their inhibitory activity against tyrosinase. The results showed that compounds 3e, 3f, 3h, 3i, 3j, and 3k possess effective tyrosinase inhibition with IC₅₀ values ranging from 7.30 μM to 62.60 μM. Particularly, compounds 3f displayed around three-fold improvement in the potency (IC₅₀ = 7.30 ± 1.15 μM) compared to that of kojic acid (IC₅₀ = 20.24 ± 2.28 μM) as the positive control. Kinetic study of compound 3f confirmed uncompetitive inhibitory activity towards tyrosinase indicating that it can bind to enzyme-substrate complex. Next, molecular docking analysis was performed to study the interactions and binding mode of the most potent compound 3f in the tyrosinase active site. Besides, the cytotoxicity of 3f, as well as its potency to reduce the melanin content were also measured on invasive melanoma B16F10 cell line. Also, 3f exhibited above 82% cell viability in the A375 cell line at 10 µM. Consequently, compounds 3f could be introduced as a potent tyrosinase inhibitor that might be a promising candidate in the cosmetics, medicine, and food industry.

Keywords: Azine derivatives; Melanin; Molecular docking; Tyrosinase inhibitors.

Fig. 1

Chemical structures of some tyrosinase inhibitors from natural or synthetic sources

Fig. 2

Molecular hybridization and fragment-based approach for designing of bis-aryl hydrazine derivatives as tyrosinase inhibitors

Scheme 1

The synthetic route for the synthesis of bis aryl hydrazine derivatives (3a–k)

Fig. 3

Lineweaver–Burk plot of mushroom tyrosinase enzyme inhibition by different concentrations of 3f in the presence of L-DOPA as a substrate. The reciprocal tyrosinase inhibitory activity was plotted against the reciprocal substrate concentration (double reciprocal plot, n = 3). K_m is the Michaelis–Menten constant and V_max is the maximum reaction velocity

Fig. 4

The binding orientation (a) and interactions (b) of compound 3f into the tyrosinase enzyme. Ligand 3f is displayed as cyan sticks, while the core residues are shown as green sticks. Hydrogen bonding, electrostatic, Pi–Pi, and alkyl-Pi interactions are displayed as green, orange, pink and light pink, respectively

Fig. 5

Effect of compound 3f on melanin content in B16F10 melanoma cells