The presented study depicts the synthesis of 11 carborane–thiazole conjugates with anticancer activity, as well as an evaluation of their biological activity as inhibitors of two enzymes: tyrosinase and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The overexpression of tyrosinase results in the intracellular accumulation of melanin and can be observed in melanoma. The overexpression of 11β-HSD1 results in an elevation of glucocorticoid levels and has been associated with the aggravation of metabolic disorders such as type II diabetes mellitus and obesity. Recently, as the comorbidity of melanomas and metabolic disorders is being recognized as an important issue, the search for new therapeutic options has intensified. This study demonstrates that carborane–thiazole derivatives inhibit both enzymes, exerting beneficial effects. The antiproliferative action of all newly synthesized compounds was evaluated using three cancer cell lines, namely A172 (human brain glioblastoma), B16F10 (murine melanoma) and MDA-MB-231 (human breast adenocarcinoma), as well as a healthy control cell line of HUVEC (human umbilical vein endothelial cells). The results show that 9 out of 11 newly synthesized compounds demonstrated similar antiproliferative action against the B16F10 cell line to the reference drug, and three of these compounds surpassed it. To the best of our knowledge, this study is the first to demonstrate dual inhibitory action of carborane–thiazole derivatives against both tyrosinase and 11β-HSD1. Therefore, it represents the first step towards the simultaneous treatment of melanoma and comorbid diseases such as type II diabetes mellitus.

This presented study depicts the synthesis of three novel carbazole–thiazole conjugates, thoroughly investigating their spectroscopic properties as well as evaluating their biological activity as tyrosinase inhibitors. Additionally, we investigated the possibility of using Concanavalin A (ConA) complexes with dyes from a theoretical point of view, developing a promising protein-based strategy of delivery of dyes to the target cells. The tyrosinase inhibition assay showed that compounds K1 and K3 demonstrated higher activity than the kojic acid with IC₅₀ values of 46 and 59 mM, respectively. Among the tested compounds, carbazole K3 exhibits the most pronounced nonlinear optical response due to its high electronic flexibility, strong solvatochromism, large excited-state dipole moments, and efficient intramolecular charge transfer. Additionally, all investigated carbazoles demonstrate high ability to form stable supramolecular complexes with ConA, which was confirmed using molecular docking studies. It was found experimentally and theoretically that the compound K3 has the best biophysical parameters, making it a promising candidate for potential diagnostic applications.