Background: Tyrosinase is involved in the melanin biosynthesis and the abnormal accumulation
of melanin pigments leading to hyperpigmentation disorders. Controlling the melanogenesis
could be an important strategy for treating abnormal pigmentation.
Methods: In the present study, a series of amide derivatives (3a-e and 5a-e) were synthesized aiming
to inhibit tyrosinase activity and melanin production. All derivatives were screened for tyrosinase
inhibition in a cell-free system. The possible interactions of amide derivatives with tyrosinase
enzyme and effect of these interactions on tyrosinase structure were checked by molecular
docking in silico and by Circular Dichroism (CD) studies, respectively. The most potent amide derivative
(5c) based on cell-free experiments, was further tested for cellular ROS inhibition and for
tyrosinase activity using mouse skin melanoma (B16F10) cells.
Results: The tyrosinase inhibitory concentration (IC50) for tested compounds was observed between
the range of 68 to 0.0029 μg/ml with a lowest IC50 value of compound 5c which outperforms
the reference arbutin and kojic acid. The cellular tyrosinase activity and melanin quantification
assay demonstrate that 15μg/ml of 5c attenuates 36% tyrosinase, 24% melanin content of
B16F10 cells without significant cell toxicity. Moreover, the zebrafish in vivo assay reveals that 5c
effectively reduces melanogenesis without perceptible toxicity. Furthermore, the molecular docking
demonstrates that compound 5c interacts with copper ions and multiple amino acids in the active
site of tyrosinase with best glide score (-5.387 kcal/mol), essential for mushroom tyrosinase
inhibition and the ability to diminish the melanin synthesis in-vitro and in-vivo.
Conclusion: Thus, we propose compound 5c as a potential candidate to control tyrosinase rooted
hyperpigmentation in the future.