Abstract
The present work describes the synthesis of few hydroxylated amide derivatives as melanogenesis inhibitors. In vitro, in vivo and computational studies proved that compound
6d
is a highly potent melanogenesis inhibitor compared to standard kojic acid. The title amides
4a
–
e
and
6a
–
e
were synthesized following simple reaction routes with excellent yields. Most of the synthesized compounds exhibited good mushroom tyrosinase inhibitory activity, but compound
6d
showed excellent activity (IC
50
0.15 µM) compared to standard kojic acid (IC
50
16.69 µM). Lineweaver–Burk plots were used for the determination of kinetic mechanism, and it was found that compounds
4c
and
6d
showed non-competitive inhibition while
6a
and
6b
showed mixed-type inhibition. The kinetic mechanism further revealed that compound
6d
formed irreversible complex with the target enzyme tyrosinase. The
Ki
values determined for compounds
4c
,
6a
,
6b
and
6d
are 0.188, 0.84, 2.20 and 0.217 µM respectively. Results of human tyrosinase inhibitory activity in A375 human melanoma cells showed that compound
6d
exhibited 91.9% inhibi-tory activity at a concentration of 50 µg/mL. In vivo cytotoxicity evaluation of compound
6d
in zebrafish embryos showed that it is non-toxic to zebrafish. Melanin depigmentation assay performed in zebrafish indicated that compound
6d
possessed greater potential in decreasing melanin contents compared to kojic acid at the same concentration. Computational studies also supported the wet lab findings as compound
6d
showed a highest binding affinity with the target protein (PDBID: 2Y9X) with a binding energy value of −7.90 kcal/mol. Molecular dynamic simulation studies also proved that amide
6d
formed the most stable complex with tyrosinase. Based upon our in vitro, in vivo and computational studies, we propose that compound
6d
is a promising candidate for the development of safe cosmetic agent.