Structure-activity relationship studies of microbiologically active thiosemicarbazides derived from hydroxybenzoic acid hydrazides

Spectroscopic characterization, molecular docking and machine learning studies of sulphur containing hydrazide derivatives

Machine learning applied in chemistry is a growing field of research. For assessing structure-property variations, this paper describes in silico studies of the hydrazide derivatives of thiosemicarbazide (TSCZ) and thiocarbohydrazide (TCHZ). The structures of TSCZ and TCHZ have been elucidated using modern spectroscopic techniques. The UV-vis spectra showed strong charge transfer transitions (π-π*) for TSCZ and TCHZ with high extinction coefficients. The NBO analysis showed orbital overlap between lp1 (N2) and σ* (C3-S4) in TSCZ and TCHZ due to intramolecular charge transfer. The first hyperpolarizabilities (β0) for TSCZ and TCHZ were found to be 0.7155 and 2.1615 × 10-30 esu, respectively, indicating their greater suitability for NLO applications as compared to standard reference urea. The strong electrophilic behaviour of TSCZ and TCHZ has been indicated by their global elecrophilicity index. The electrophilic reactivity descriptor analysis indicated that the investigated molecules could serve as precursors for the targeted synthesis of new heterocyclic derivatives. The docking studies showed appreciable binding energies with target proteins having PDB IDs 2WJE and 6CLU of Gram-positive bacteria, namely, Streptococcus pneumoniae phosphatase (PTP-CPS4B) and Staphylococcus aureus dihydropteroate synthase (saDHPS), respectively, for TSCZ and TCHZ, predicting good antimicrobial activity.

Design, Synthesis, Antibacterial Evaluations and In Silico Studies of Novel Thiosemicarbazides and 1,3,4-Thiadiazoles

The emergence of drug-resistant bacterial strains continues to be one of the major challenges of medicine. For this reason, the importance of searching for novel structures of antibacterial drugs chemically different from the currently known antibiotics is still of great importance. In this study, we synthesized the thiosemicarbazide and 1,3,4-thiadiazole derivatives and tested them for antibacterial activity. In in vitro tests, we examined the activity of the synthesized substances against Gram-positive and Gram-negative bacteria strains. While all 1,3,4-thiadiazoles tested lacked significant activity, the antimicrobial response of the thiosemicarbazides was moderate and it was also dependent on the type and position of the substituent on the phenyl ring. The highest activity towards all Gram-positive bacteria strains was shown by all three linear compounds containing the trifluoromethylphenyl group in the structure. The MIC (minimum inhibitory concentration) values were in the range of 3.9–250 µg/mL. Additionally, we try to explain the mechanism of the antibacterial activity of the tested compounds using the molecular docking to DNA gyrase and topoisomerase IV, following previous reports on the molecular basis of the activity of thiosemicarbazides. Docking simulations allow the purposing dual mechanism of the antibacterial activity of the synthesized compounds through inhibition of topoisomerase IV DNA gyrase with the moderate prevalence of the topoisomerase pathway.

Synthesis, characterization, DFT calculation, antioxidant activity, ADMET and molecular docking of thiosemicarbazide derivatives and their Cu (II) complexes

In this work, new thiosemicarbazides (ECA-1, ECA-2) and their Cu (II) complexes (ECA-1-Cu, ECA-2-Cu) were synthesized and their structures were characterized by ¹H NMR, ¹³C NMR, FT-IR, LC-MS, UV-Vis, and thermogravimetric analysis methods. Also, the surface morphology of the all compounds were examined by SEM (Scanning Electron Microscope). In the second stage, in vitro antioxidant capacity of the obtained compounds was investigated. The evaluation of the antioxidant properties of both synthesized ligands and complexes in this study was carried out by DPPH and FRAP methods. According to the results, both complexes exhibited more antioxidant capacity than the corresponding ligands. When antioxidant effects are compared for DPPH (SC₅₀ = 5.27 ± 0.05 μM) and for FRAP (7845.69 ± 16.75 mmolTE/g), compound ECA-2-Cu appears to have the best inhibition effect. The complexes were found non-electrolytic in nature with melting point of above 250 °C, and electronic spectra and magnetic behavior demonstrated that the complexes were found to be tetrahedral geometry. Further, in silico the ADMET properties which studies are a significant role in improving and predicting drug compounds were calculated using web-based platforms. The theoretical calculations were made using the method of Density Functional Theory (Frontier molecular orbital analyze and Nonlinear optical properties). Also, molecular docking studies were performed to evaluate the binding interactions between the ligand and complex compounds and Human Peroxiredoxin 2. Both in vitro and in silico results indicated that synthesized compounds could act as potent antioxidant agents.

Synthesis, molecular docking, and evaluation of antibacterial activity of 1,2,4-triazole-norfloxacin hybrids

A series of 1,2,4-triazole-norfloxacin hybrids was designed, synthesized, and evaluated for in vitro antibacterial activity against common pathogens. All the newly synthesized compounds were characterized by Fourier-transform infrared spectrophotometry, proton and carbon nuclear magnetic resonance, and electrospray ionization-mass spectrometry. Representative compounds from each step of the synthesis were further characterized by X-ray crystallography. Many of the compounds synthesized exhibited antibacterial activity superior to that of norfloxacin toward both, gram-positive and gram-negative bacteria. The toxicity of the 1,2,4-triazole-norfloxacin hybrids toward bacterial cells was 32-512 times higher than that toward mouse fibroblast cells. Moreover, hemolysis was not observed at concentrations of 64 μg/mL, suggesting good biocompatibility. Molecular docking showed a least binding energy of -9.4 to -9.7 kcal/mol, and all compounds were predicted to show remarkable affinity for the bacterial topoisomerase IV.

Docking and QSAR of Aminothioureas at the SARS-CoV-2 S-Protein-Human ACE2 Receptor Interface

Docking of over 160 aminothiourea derivatives at the SARS-CoV-2 S-protein–human ACE2 receptor interface, whose structure became available recently, has been evaluated for its complex stabilizing potency and subsequently subjected to quantitative structure–activity relationship (QSAR) analysis. The structural variety of the studied compounds, that include 3 different forms of the N–N–C(S)–N skeleton and combinations of 13 different substituents alongside the extensive length of the interface, resulted in the failure of the QSAR analysis, since different molecules were binding to different parts of the interface. Subsequently, absorption, distribution, metabolism, and excretion (ADME) analysis on all studied compounds, followed by a toxicity analysis using statistical models for selected compounds, was carried out to evaluate their potential use as lead compounds for drug design. Combined, these studies highlighted two molecules among the studied compounds, i.e., 5-(pyrrol-2-yl)-2-(2-methoxyphenylamino)-1,3,4-thiadiazole and 1-(cyclopentanoyl)-4-(3-iodophenyl)-thiosemicarbazide, as the best candidates for the development of future drugs.

Synergistic Effects of Thiosemicarbazides with Clinical Drugs against S. aureus

Antimicrobial resistance spurred by the overuse and misuse of antibiotics is a major global health concern, and of the Gram positive bacteria, S. aureus is a leading cause of mortality and morbidity. Alternative strategies to treat S. aureus infections, such as combination therapy, are urgently needed. In this study, a checkerboard method was used to evaluate synergistic interactions between nine thiosemicarbazides (4-benzoyl-1-(2,3-dichloro-benzoyl)thiosemicarbazides 1-5 and 4-aryl-1-(2-fluorobenzoyl)thiosemicarbazides 6-9) and conventional antibiotics against S. aureus ATCC 25923, which were determined as the fractional inhibitory concentration indices (FICIs). For these experiments, amoxicillin, gentamicin, levofloxacin, linezolid, and vancomycin were selected to represent the five antimicrobial classes most commonly used in clinical practice. With one exception of 7-vancomycin combination, none of the forty-five thiosemicarbazide-antibiotic combinations tested had an antagonistic effect, showing promising results with respect to a combination therapy. The synergic effect was observed for the 2-linezolid, 4-levofloxacin, 5-linezolid, 6-gentamicin, 6-linezolid, and 7-levofloxacin combinations. No interactions were seen in combination of the thiosemicarbazide with gentamicin or vancomycin, whereas all combinations with linezolid acted in additive or synergism, except for 6-gentamicin and 7-linezolid. The 4-(4-chlorophenyl)-1-(2-fluorobenzoyl)thiosemicarbazide 6 showed a clear preference for the potency; it affected synergistically in combinations with gentamicin or linezolid and additively in combinations with amoxicillin, levofloxacin, or vancomycin. In further studies, the inhibitory potency of the thiosemicarbazides against S. aureus DNA gyrase and topoisomerase IV was examined to clarify the molecular mechanism involved in their synergistic effect in combination with levofloxacin. The most potent synergist 6 at concentration of 100 µM was able to inhibit ~50% activity of S. aureus DNA gyrase, thereby suggesting that its anti-gyrase activity, although weak, may be a possible factor contributing to its synergism effect in combination with linezolid or gentamycin.

Development of 3,5-Dinitrophenyl-Containing 1,2,4-Triazoles and Their Trifluoromethyl Analogues as Highly Efficient Antitubercular Agents Inhibiting Decaprenylphosphoryl-β-d-ribofuranose 2'-Oxidase

We report herein the discovery of 3,5-dinitrophenyl 1,2,4-triazoles with excellent and selective antimycobacterial activities against Mycobacterium tuberculosis strains, including clinically isolated multidrug-resistant strains. Thorough structure-activity relationship studies of 3,5-dinitrophenyl-containing 1,2,4-triazoles and their trifluoromethyl analogues revealed the key role of the position of the 3,5-dinitrophenyl fragment in the antitubercular efficiency. Among the prepared compounds, the highest in vitro antimycobacterial activities against M. tuberculosis H₃₇Rv and against seven clinically isolated multidrug-resistant strains of M. tuberculosis were found with S-substituted 4-alkyl-5-(3,5-dinitrophenyl)-4H-1,2,4-triazole-3-thiols and their 3-nitro-5-(trifluoromethyl)phenyl analogues. The minimum inhibitory concentrations of these compounds reached 0.03 μM, which is superior to all the current first-line anti-tuberculosis drugs. Furthermore, almost all compounds with excellent antimycobacterial activities exhibited very low in vitro cytotoxicities against two proliferating mammalian cell lines. The docking study indicated that these compounds acted as the inhibitors of decaprenylphosphoryl-β-d-ribofuranose 2'-oxidase enzyme, which was experimentally confirmed by two independent radiolabeling experiments.

Synthesis and Antibacterial Activity of New Thiazolidine-2,4-dione-Based Chlorophenylthiosemicarbazone Hybrids

Series of new thiazolidine-2,4-dione-based chlorophenylthiosemicarbazone hybrids (17–40) were synthesized by the reaction of condensation chlorophenylthiosemicarbazides with formylphenyl 2-(2,4-dioxothiazolidin-5-yl/ylidene)acetates. New compounds were tested on reference strains of Gram-positive and Gram-negative bacteria. The antibacterial activity of target compounds was determined by broth dilution method. Most active compounds possess minimum inhibitory concentration (MIC) = 3.91 mg/L. These compounds were non-toxic at concentrations close to their antibacterial effect. The antibacterial activity of some compounds was similar to or higher than the activity of used reference drugs such as oxacillin and cefuroxime. The structure–activity relationships (SARs) analysis collectively suggests that at least two different molecular mechanisms of their antibacterial activity should be expected.

Determination of the primary molecular target of 1,2,4-triazole-ciprofloxacin hybrids

We have synthesized and examined the antibacterial activity, toxicity and affinity towards bacterial type II topoisomerases of a series of 1,2,4-triazole-ciprofloxacin hybrids. A number of these compounds displayed enhanced activity against Gram-positive and Gram-negative bacteria when compared to ciprofloxacin. The toxic concentrations of the obtained derivatives, evaluated on HEK-293 cells using MTT assay, were much higher than concentrations required to produce antibacterial effect. Finally, the results of enzymatic studies showed that the analyzed compounds demonstrated other preferences as regards primary and secondary molecular targets than ciprofloxacin.