Hyperpigmentation can be prevented by regulating melanin synthesis through tyrosinase inhibition. As such, tyrosinase inhibitors like arbutin, kojic acid, and hydroquinone are commonly used for skin lightening. Recent studies suggest that certain pyrazole derivatives with tyrosinase activity may also have anticancer potential by influencing melanocyte transformation and tumor progression, positioning them as promising candidates for both cosmetic and therapeutic uses. The aim of this study was to evaluate the tyrosinase inhibitory activity of carbothioamidopyrazole derivatives. Inhibition was determined using the Dixon method, leveraging in silico molecular docking and circular dichroism (CD) spectroscopy to analyze fluorescence quenching. Carbothioamidopyrazole derivatives at the C-3 and C-5 positions in the pyrazole ring may be effective alternatives to traditional skin-lightening agents. These derivatives can induce structural changes in tyrosinase, thus altering its activity, and influence melanocyte transformation. Their dual action as tyrosinase inhibitors and potential anticancer agents makes them valuable for future research. Two compounds exhibited stronger inhibitory activity than kojic acid. Molecular docking suggests that these derivatives may block tyrosinase activity by preventing substrate access to its active site. These results underscore the potential of pyrazole derivatives for both cosmetic and therapeutic applications.

The present study describes the coordination properties of a reduced Schiff base, N-(2-hydroxybenzyl)alanine, towards cobalt(II) using potentiometric as well as spectroscopic (UV-Vis and ESI-MS) methods. The results indicate the formation of six mononuclear complexes showing high stability in aqueous solution. Coordination occurs in the {O⁻_phenolic,N,O⁻_carboxyl} and {N,O⁻_carboxyl} chelation modes, depending on the degree of ligand deprotonation. Examination of the complexation equilibria at pH ca 7, which is important from a biological point of view, allowed to identify two species: [CoL] and [CoL₂H]⁻. The kinetic analysis showed a structural change of those cobalt(II) complexes from octahedral to tetrahedral in accordance with a first-order time relationship. The antimicrobial properties of N-(2-hydroxybenzyl)alanine, cobalt(II) nitrate and of the Co(II) – ligand complexes were determined against Gram-positive bacteria (Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis), Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Helicobacter pylori) and a fungal strain (Candida). The results indicate that the complexes are more active for more strains than the ligand alone. Nevertheless, the complexes induce a higher decrease in the metabolic activity of cells but without damage to nuclei. Tetrahedral structures show stronger anti-cellular toxicity than octahedral complexes, which is most likely due to the higher accessibility of the cobalt(II) center.