Discovery of novel isatin-based thiosemicarbazones: synthesis, antibacterial, antifungal, and antimycobacterial screening

Tripeptides conjugated with thiosemicarbazones: new inhibitors of tyrosinase for cosmeceutical use

The development of skin-care products is recently growing. Cosmetic formulas containing active ingredients with proven efficacy, namely cosmeceuticals, are based on various compounds, including peptides. Different whitening agents featuring anti-tyrosinase activity have been applied in the cosmeceutical field. Despite their availability, their applicability is often limited due to several drawbacks including toxicity, lack of stability, and other factors. In this work, we present the inhibitory effect on diphenolase activity of thiosemicarbazone (TSC)-peptide conjugates. Tripeptides FFY, FWY, and FYY were conjugated with three TSCs bearing one or two aromatic rings via amide bond formation in a solid phase. Compounds were then examined as tyrosinase and melanogenesis inhibitors in murine melanoma B16F0 cell line, followed by the cytotoxicity assays of these cells. In silico investigations explained the differences in the activity, observed among tested compounds. Mushroom tyrosinase was inhibited by TSC1-conjugates at micromolar level, with IC₅₀ lower than this for kojic acid, a widely used reference compound. Up to now, this is the first report regarding thiosemicarbazones conjugated with tripeptides, synthesised for the purpose of tyrosinase inhibition.

5-Methoxyisatin N(4)-Pyrrolidinyl Thiosemicarbazone (MeOIstPyrd) Restores Mutant p53 and Inhibits the Growth of Skin Cancer Cells, In Vitro

A series of novel thiosemicarbazone derivatives containing 5-methoxy isatin were designed and synthesized with modification on N(4) position. Derivatives considering structure-activity relationship have been designed and synthesized by condensing thiosemicarbazide with 5-methoxy isatin. The synthesized compounds were characterized by elemental analysis, FT-IR spectroscopy, UV-visible spectroscopy, NMR (1H, 13C) spectroscopy, mass spectrometry, and a single-crystal study. Biological evaluation of the synthesized compounds revealed that MeOIstPyrd is the most promising compound against skin cancer cell line, A431, with an IC50 value of 0.9 μM. In addition, MeOIstPyrd also exhibited low toxicity against the normal human fibroblast and the human embryonic kidney 293 cell line, HLF-1, and HEK293, respectively. Furthermore, the mechanistic study revealed that MeOIstPyrd efficiently inhibited cell proliferation, migration, and spheroid formation by activating the mitochondrial intrinsic apoptotic pathway. MeOIstPyrd also induces DNA damage and activates p53 irrespective of the p53 status. It increases the half-life of p53 and stabilizes p53 by phosphorylating it at ser15. Moreover, MeOIstPyrd was found to bind to MDM2 in the p53 sub-pocket and, therefore, block p53-MDM2 interaction. Our result exhibited potential anticancer activity of MeOIstPyrd in the A431 cell line and its ability in restoring mutant p53, which is an interesting and promising strategy for cancer therapeutics.

QSAR Studies, Molecular Docking, Molecular Dynamics, Synthesis, and Biological Evaluation of Novel Quinolinone-Based Thiosemicarbazones against Mycobacterium tuberculosis

In this study, a series of novel quinolinone-based thiosemicarbazones were designed in silico and their activities tested in vitro against Mycobacterium tuberculosis (M. tuberculosis). Quantitative structure-activity relationship (QSAR) studies were performed using quinolinone and thiosemicarbazide as pharmacophoric nuclei; the best model showed statistical parameters of R² = 0.83; F = 47.96; s = 0.31, and was validated by several different methods. The van der Waals volume, electron density, and electronegativity model results suggested a pivotal role in antituberculosis (anti-TB) activity. Subsequently, from this model a new series of quinolinone-thiosemicarbazone 11a-e was designed and docked against two tuberculosis protein targets: enoyl-acyl carrier protein reductase (InhA) and decaprenylphosphoryl-β-D-ribose-2'-oxidase (DprE1). Molecular dynamics simulation over 200 ns showed a binding energy of -71.3 to -12.7 Kcal/mol, suggesting likely inhibition. In vitro antimycobacterial activity of quinolinone-thiosemicarbazone for 11a-e was evaluated against M. bovis, M. tuberculosis H37Rv, and six different strains of drug-resistant M. tuberculosis. All compounds exhibited good to excellent activity against all the families of M. tuberculosis. Several of the here synthesized compounds were more effective than the standard drugs (isoniazid, oxafloxacin), 11d and 11e being the most active products. The results suggest that these compounds may contribute as lead compounds in the research of new potential antimycobacterial agents.

Novel N-substituted indole hydrazones as potential antiplatelet agents: synthesis, biological evaluations, and molecular docking studies

Background and purpose:

Antiplatelet agents can diminish the chance of coronary heart diseases due to the prevention of unusual clotting in the arteries by inhibiting platelet aggregation and avoiding the formation of a blood clot. This mechanism can help to prevent ischemic stroke likewise. To improve the activity of these drugs and reduce their side effects, further studies are required.

Experimental approach:

Based on the previous studies representing the promising antiplatelet activity of indole hydrazones, a series of their homologs containing twenty-one compounds were prepared in two steps. First, alkylation reaction on the nitrogen of the indole ring, and second, chiff base formation by condensation of a primary amine and N-substituted indole-3 carbaldehyde. Consequently, their platelet anti-aggregation activity was evaluated based on the Born turbidimetric method.

Findings/Results:

Most of the compounds exhibited noticeable activity against platelet aggregation induced by arachidonic acid. Amongst them, two compounds 2e and 2f showed higher activity with IC₅₀ values that made comparable to indomethacin and acetylsalicylic acid as standard drugs and had no toxicity on platelets.

Conclusion and implications:

The synthesized compounds exhibited promising activity against arachidonic acid-induced aggregation; however, none of them showed noticeable antiplatelet activity induced by adenosine di-phosphate. Chemical structure comparison of the prepared derivatives indicated the existence of a lipophilic medium-sized group on the phenyl ring increased their activity. In addition, the docking studies confirmed this hydrophobic interaction in the lipophilic pocket of cyclooxygenase-1 enzyme suggesting that hydrophobicity of this region plays a pivotal role in the anti-platelet activity of these compounds. To prove this finding, the enzymatic evaluation with the target enzyme is required.

Synthesis of 4-[(1H-Benzimidazol-2-yl)sulfanyl]benzaldehyde and 2-({4-[(1H-Benzimidazol-2-yl)sulfanyl]phenyl}methylidene)hydrazine-1-carbothioamide

Here we describe the preparation of 2-(4-((1H-benzo[d]imidazol-2-yl)thio)-benzylidene)-hydrazine-1-carbothioamide in two steps. In the first step, 1,3-dihydro-2H-1,3-benzimidazole-2-thione was reacted with 4-fluorobenzaldehyde in DMSO to get 4-[(1H-benzimidazol-2-yl)sulfanyl]benzaldehyde in high yield. The reaction of the obtained aldehyde with thiosemicarbazide in ethanol at reflux temperature yielded 2-({4-[(1H-benzimidazol-2-yl)sulfanyl]phenyl}methylidene)hydrazine-1-carbothioamide. The structure of the synthesized compounds was established by NMR spectroscopy (1H, 13C), mass spectrometry, and infrared spectroscopy.

5-Aryl-1-Arylideneamino-1H-Imidazole-2(3H)-Thiones: Synthesis and In Vitro Anticancer Evaluation

A novel series of N-1 arylidene amino imidazole-2-thiones were synthesized, identified using IR, ¹H-NMR, and ¹³C-NMR spectral data. Cytotoxic effect of the prepared compounds was carried out utilizing three cancer cell lines; MCF-7 breast cancer, HepG2 liver cancer, and HCT-116 colon cancer cell lines. Imidazole derivative 5 was the most potent of all against three cell lines. DNA flow cytometric analysis showed that, imidazoles 4d and 5 exhibit pre-G1 apoptosis and cell cycle arrest at G2/M phase. The results of the VEGFR-2 and B-Raf kinase inhibition assay revealed that compounds 4d and 5 displayed good inhibitory activity compared with reference drug erlotinib.