부산대학교 도서관

The present thesis describes synthesis of some hydroxylated amide derivatives as melanogenesis inhibitors. The in vitro, in vivo and in silico studies proved that one of the derivatives is highly potent melanogenesis inhibitor compared to standard kojic acid. The title amides 4a-e and 6a-e were synthesized by following the simple reaction routes with excellent yields. Most of the synthesized compounds exhibited good mushroom tyrosinase inhibitory activity but compound 6d showed excellent activity with (IC50 0.15µM) compared to standard kojic acid (IC50 16.69µM). 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 are mixed-type inhibitors. 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 0.188µM, 0.84µM, 2.20µM and 0.217µM respectively. Human tyrosinase inhibitory activity results in A375 human melanoma cells showed that compound 6d exhibited 91.87% inhibition. The in vivo cytotoxicity evaluation of the 6d in zebrafish embryos showed that it is nontoxic to zebrafish. The melanin depigmentation assay was performed in zebrafish and results indicated that compound 6d having greater potential to decrease the melanin contents compared to kojic acid at same concentration. The in silico studies also support the wet lab findings as the compound 6d has highest binding affinity with the target protein (PDBID: 2Y9X) with binding energy value (-7.90 kcal/mol). The molecular dynamic simulation studies also proved that amide 6d formed the most stable complex with tyrosinase. Based upon our in vitro, in vivo and in silico studies we may propose that the 6d is promising candidate for the development of safe cosmetic agent. (Chapter 1)Herbal nanoparticles gain lots of attention because of their pharmaceutical importance. The present study reports the eco-friendly synthesis, characterization and their tyrosinase activity of silver nanoparticles (AgNPs) using an aqueous extract of Bidens frondosa. The appearance of brown color indicated the formation of B. frondosa AgNPs. The Formation of AgNPs was confirmed by UV–Vis spectroscopy, FTIR, FESEM and EDS analysis. The formation of herbal AgNPs of size ranging 20-70 nm further were assured by energy dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscopy (FESEM). The mushroom tyrosinase inhibitory activity of synthesized AgNPs was evaluated. Nanoparticles were found to have significantly higher tyrosinase inhibitory activity compared to control. The IC50 values of crude extract, AgNP and Kojic acid were found to be 9, 15, and 2.37 μg/mL, respectively. AgNPs of B. frondosa may be considered as a potential candidate for the production of medical and cosmetic products. (Chapter 2)Melanin is the major factor that determines skin color and protects from ultraviolet radiations. In present thesis we evaluated the anti-melanogenesis effect of acetazolamide (ACZ) using four different approaches (enzyme kinetic, in vitro, in vivo and in silico). ACZ demonstrated significant inhibitory activity (IC50 7.895 ± 0.24 µM) against tyrosinase as compared to the standard drug Kojic acid (IC50 16.84 ± 0.64 µM) and kinetic analyses showed that ACZ is a non-competitive inhibitor without cytotoxic effect. In in vitro experiments, A375 human melanoma cells were treated with 20 or 40 µM of ACZ with or without 50 µM of L-DOPA. Western blot results showed that ACZ significantly (p