Pyrazole derivatives as antileishmanial agents: Biological evaluation, molecular docking study, DFT analysis and ADME prediction

Leishmaniasis is a parasitic disease that is commonly found in tropical and sub-tropical regions. Currently, there is no protective antileishmanial vaccine, and the available clinical drugs have serious side effects. On the other hand, due to the emergence of multidrug-resistant strains of the causative pathogens, the study and design of novel antileishmanial agents is urgently needed. Accordingly, fourteen previously synthesized pyrazole and pyrano [2,3-c] pyrazole derivatives (P 1 -P 14 ) were evaluated for antileishmanial efficacy against the protozoan parasite, Leishmania major. Among the tested compounds, seven derivatives including P 1 , P 3 , P 5 , P 8 , P 12 , P 13 , and P 14 exhibited promising antileishmanial activity with IC50 values in the range of 34.79-43.55 μg/mL, compared to the standard drug (Glucantime) with an IC50 value of 97.31 μg/mL. In the case of pyrazole derivatives, P 1 , P 5 , and P 8 exhibited significant antileishmanial activity with IC50 values of 35.53, 36.79, and 37.40 μg/mL, respectively. The most potent antileishmanial activity is belong to P 12 and P 14 , with IC50 values of 34.79 and 38.51 μg/mL, respectively. Molecular docking outputs presented that P 12 and P 14 formed favorable interactions with key residues in the active site of the 14-alpha demethylase enzyme, which is an important target for antileishmanial agents. Various DFT parameters were also calculated for compounds P 1 and P 12 , which were the most and least active compounds, respectively. The outputs indicated that compound P 1 was more thermodynamically stable than P 12 . Additionally, P 1 had higher hardness and a higher energy gap, resulting in greater stability. In addition, these compounds showed satisfactory theoretical ADME properties. The present results indicate that the investigated pyrazole and pyrano [2,3-c] pyrazole derivatives can be considered as promising agents for the development of antileishmaniasis treatments.

Synthesis and Structure-Activity Relationship of Thiourea Derivatives Against Leishmania amazonensis

Background: Leishmaniasis, caused by Leishmania protozoa and transmitted by vectors, presents varied clinical manifestations based on parasite species and host immunity. The lack of effective vaccines or treatments has prompted research into new therapies, including thiourea derivatives, which have demonstrated antiprotozoal activities. Methods: We synthesized two series of N,N'-disubstituted thiourea derivatives through the reaction of isothiocyanates with amines. These compounds were evaluated in vitro against promastigote and amastigote forms of L. amazonensis, alongside cytotoxicity assessments on macrophages. In silico studies were conducted to analyze structure-activity relationships (SARs) and drug-likeness. Results: A total of fifty thiourea derivatives were synthesized and tested. Compound 3e from the first generation exhibited significant anti-leishmanial activity with an IC50 of 4.9 ± 1.2 µM and over 80-fold selectivity compared to that of miltefosine (IC50 = 7.5 ± 1.2 µM). The introduction of a piperazine ring in the second-generation thioureas enhanced potency and selectivity, with compound 5i achieving an IC50 of 1.8 ± 0.5 µM and a selectivity index of approximately 70. Pharmacokinetic predictions indicated favorable profiles for the active compounds. Conclusions: SAR and ADMET analyses identified compound 5i as the most promising candidate for further preclinical evaluation, suggesting that piperazine thiourea derivatives represent a novel class of anti-leishmanial agents.

Antileishmanial potential of thiourea-based derivatives: design, synthesis and biological activity

Leishmaniasis is a neglected tropical disease caused by protozoan parasites and transmitted to humans by the sandfly vector. Currently, the disease has limited therapeutic alternatives. Thiourea derivatives were designed, synthesized, and screened for antileishmanial activity. The synthesized compounds 4g, 20a, and 20b demonstrated significant in vitro potency against L. major, L. tropica, and L. donovani promastigotes with IC50 values at low submicromolar concentrations. Compound 4g showed the highest activity against the amastigotes of L. major. In enzyme inhibition assays, compounds 4g, 20a, and 20b demonstrated good inhibitory potential against L. major dihydrofolate reductase (DHFR) and pteridine reductase 1 (PTR1). Reversal of the antileishmanial effect by adding folic acid revealed that the compounds 4g, 20a, and 20b act through an antifolate mechanism. Cytotoxicity data on normal human embryonic kidney cells (HEK-293) showed that the synthesized compounds displayed better safety profiles. Docking experiments on the enzymes L. major DHFR and PTR1 demonstrated the significant interactions with the active pocket residues of the target enzymes.

New Prospective Insecticidal Agents Based on N-(arylcarbamothioyl)arylmide Derivatives Against Spodoptera frugiperda: Design, Synthesis, Toxicological, Biological, Biomedical Studies and Antibacterial Activity

In this work, a novel series of N-(arylcarbamothioyl)arylmide) 2-11 were synthesized by treating One-Pot three-multicomponent of Aroyl chloride, ammonium isothiocyanate and amine compounds under refluxing conditions. Using spectroscopic methods, the chemical structure of the novelty developed compounds were investigated. After five days, the proposed derivatives' insecticidal bioassay was assessed using the median lethal concentration (LC50) against the second & fourth larvae of Spodoptera frugiperda as toxicity agents. The findings showed that, to varying degrees, every tested substance exerted insecticidal effects on S. frugiperda larvae in both of their instars. Compound 9 was the most poisonous of them all, having an LC50 against larvae in their second and fourth instars of 60.45 and 123.21 mg/L, respectively. Additionally, a few biological and biochemical characteristics of the substances that were generated in a lab setting were also looked at. Furthermore, this work discusses how to discover novel compounds that may one day be employed as insecticidal agents. Finally, all the designed components were monitored for their antibacterial effectiveness toward both Gram-positive & Gram-negative bacteria.

Synthesis, crystal structure analysis, computational modelling and evaluation of anti-cervical cancer activity of novel 1,5-dicyclooctyl thiocarbohydrazone

Thiocarbazones are widely used as bioactive and pharmaceutical intermediates in medicinal chemistry and have been shown to exhibit diverse biological and pharmacological activities such as antimicrobial, anticancer, anti-viral, anti-convulsant and anti-inflammatory etc. In continuation of our interest in biologically active heterocycles and in an attempt to synthesize a spiro derivative, 1,2,4,5-tetraazaspiro[5.7]tridecane-3-thione, herein, the synthesis of 1,5-dicyclooctyl thiocarbohydrazone (3) has been reported via reaction of the cyclooctanone and thiocarbohydrazide. The structure was assigned on the basis of detailed spectral analysis and also confirmed by X-ray crystal studies. The Hirshfeld surface analysis indicates that the most significant interaction is S⋯H (12.7%). The presentation of mechanistic aspects regarding the plausible route of its formation has also been included. The first hyperpolarizability (β0) was found to be 10.22 × 10-30 esu, which indicates that the compound exhibits good non-linear optical properties. The density functional theory (DFT) method has been used to characterize the spectroscopic properties and vibrational analysis of 1,5-dicyclooctyl thiocarbohydrazone (3) theoretically. The compound and cisplatin (standard) were screened for their antiproliferative activity against the human cervical cancer cell line (SiHa) and they exhibited significant activity with IC50 values of 250 μM and 15 μM, respectively. The inhibitory nature of the title compound against viral oncoprotein E6 was confirmed by studies using molecular docking analysis. The results of biological activity and in silico analysis indicate that the synthesized molecule could act as a precursor for the synthesis of new heterocyclic derivatives of medicinal importance.

Sulfur- and Amine- Promoted Multielectron Autoredox Transformation of Nitromethane: Multicomponent Access to Thiourea Derivatives

Thiourea derivatives are in-demand motifs in organic synthesis, medicinal chemistry and material science, yet redox methods for the synthesis that start from safe, simple, inexpensive and readily available feedstocks are scarce. In this article, we disclose the synthesis of these motifs using elemental sulfur and nitromethane as the starting materials. The method harnesses the multi-electron auto-redox property of nitromethane in the presence of sulfur and amines, delivering thiourea products without any added oxidant or reductant. Extension of this reaction to cyclizable amines and/or higher homologues of nitromethane led to a wide range of nitrogen heterocycles and thioamides. Operationally simple, the reactions are scalable, tolerate a wide range of functional groups, and can be employed for the direct functionalization of natural products. Mechanistically, the nitro group was found to act as an oxidant leaving group, being reduced to ammonia whereas sulfur, along with the role of a sulfur building block for the thiocarbonyl group, behaved as a complementary reductant, being oxidized to sulfate.

Electrochemical NaI-mediated one-pot synthesis of guanidines from isothiocyanates via tandem addition-guanylation

In this study, we present an electrochemical approach for the synthesis of guanidines from isothiocyanates and amines in a single reaction vessel. This one-pot operation takes place in aqueous media, utilizing an undivided cell setup with NaI serving as both the electrolyte and mediator. The process involves the in situ generation of thiourea, followed by electrolytic guanylation with amines. Under ambient temperature conditions, we successfully demonstrated the formation of 30 different guanidine compounds, achieving yields ranging from fair to excellent. Furthermore, the synthesis method could be carried out on a gram scale with a good yield. This protocol stands out for its cost-effectiveness, step-economical design, high tolerance towards various functional groups, and environmentally friendly reaction conditions.

Antiprotozoal Activity of Benzoylthiourea Derivatives against Trypanosoma cruzi: Insights into Mechanism of Action

For decades, only two nitroheterocyclic drugs have been used as therapeutic agents for Chagas disease. However, these drugs present limited effectiveness during the chronic phase, possess unfavorable pharmacokinetic properties, and induce severe adverse effects, resulting in low treatment adherence. A previous study reported that N-(cyclohexylcarbamothioyl) benzamide (BTU-1), N-(tert-butylcarbamothioyl) benzamide (BTU-2), and (4-bromo-N-(3-nitrophenyl) carbamothioyl benzamide (BTU-3) present selective antiprotozoal activity against all developmental forms of Trypanosoma cruzi Y strain. In this study, we investigated the mechanism of action of these compounds through microscopy and biochemical analyses. Transmission electron microscopy analysis showed nuclear disorganization, changes in the plasma membrane with the appearance of blebs and extracellular arrangements, intense vacuolization, mitochondrial swelling, and formation of myelin-like structures. Biochemical results showed changes in the mitochondrial membrane potential, reactive oxygen species content, lipid peroxidation, and plasma membrane fluidity. In addition, the formation of autophagic vacuoles was observed. These findings indicate that BTU-1, BTU-2, and BTU-3 induced profound morphological, ultrastructural, and biochemical alterations in epimastigote forms, triggering an autophagic-dependent cell death pathway.

Synthesis, antileishmanial activity and molecular modeling of new 1-aryl/alkyl-3-benzoyl/cyclopropanoyl thiourea derivatives

Due to the lack of effective vaccine(s) against leishmania and also pharmacokinetics issues of current drugs, it is necessary to discover new antileishmanial agents. Within this particular study, a series of novel 1-aryl/alkyl-3-benzoyl/cyclopropanoyl thiourea derivatives were synthesized (yields 69-84%) and evaluated as antileishmanial compounds (1-11). Synthetic derivatives were subjected to in vitro antileishmanial assessment against Leishmania major promastigotes by colorimetric MTT assay. Compounds 3 (IC50 38.54 µg/mL), 5 (IC50 84.75 µg/mL) and 10 (IC50 70.31 µg/mL) exhibited higher activities after 48 h but were less potent than amphotericin B (IC50 0.19 µg/mL). Antileishmanial activities indicated priority of 5-methyl-4-phenyl thiazole over furyl methyl substituents and 4-phenyl thiazole on thiourea nitrogen. N-myristoyltransferase (NMT) was selected as a validated L. major target for molecular docking studies. In silico results indicated the contribution of hydrophobic, π-stacking and H-bond interactions in binding to target. Most of the synthesized derivatives had lower binding affinities to human NMT (hNMT) than leishmanial enzyme. Docking conformations of top-ranked selective binders (compounds 3 and 5) were subjected to 50 ns MD simulations inside L. major HMT (LmNMT) active site. MD trajectories were used to extract RMSD, RMSF, Rg and durability of intramolecular/intermolecular H-bonds of the complex. It was observed that compound 3 escaped from LmNMT binding site during simulation period and no stable complex could be envisaged. Unlike 3, compound 5 attained stable binding conformation with converged stability parameters. Although mechanistic details for antileishmanial effects of synthesized derivatives are to be explored, current results may be implicated in further structure-guided approach toward potent antileishmanial agents.

Novel imino-thiazoloquinoxaline derivatives against renal cell carcinoma: less radiation-damaging approach

Renal cell carcinoma (RCC) is the most fatal tumor in the urinary system. Resistance development and unmet effective responses, request new anticancer agents with better therapeutic index. Ten new imino-thiazolo-quinoxaline derivatives (5a-j) were synthesized and preliminary evaluated for downregulation of Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) activity taking sorafenib as a reference drug. Compounds 5d & 5h showed potent inhibition to VEGFR-2 activity at IC50 89.35 nM & 60.64 nM, respectively, then they both were further evaluated in-vitro against urinary bladder cancer cell line T-24 taking sorafenib as a reference drug. Compound 5h displayed nearly anticancer activity to sorafenib against T-24 cell line in all concentrations tested except at concentration 10 µM where it highly suppressed cell viability to 6.71 % compared to 15.15% of sorafenib. Compound 5h was then evaluated for its ameliorative efect against radiation induced renal tissue injury. Assessment of pro-angiogenic (VEGFR-2), pro-fibrotic (transforming growth factor-beta 1 (TGF-β1)) and apoptotic (caspase-3) markers, as well as histopathological examinations were performed on kidney of irradiated mice. Results showed ability of compound 5h to downregulate VEGFR-2 activity and its cytotoxic effect against RCC, in addition to mitigation of radiation induced renal tissue injury. Ethyl imino-thiazoloquinoxaline carboxylate derivative 5h showed a potential cytotoxic activity against RCC and could be considered a promosing alleviative candidate when employed post radiotherapy regimen.

Graphical Abstract

Recent trends in chemistry, structure, and various applications of 1-acyl-3-substituted thioureas: a detailed review

The interest in acyl thioureas has continually been escalating owing to their extensive applications in diverse fields, such as synthetic precursors of new heterocycles, pharmacological and materials science, and technology. These scaffolds exhibit a wide variety of biological activities such as antitumor, enzyme inhibitory, anti-bacterial, anti-fungal, and anti-malarial activities and find utilization as chemosensors, adhesives, flame retardants, thermal stabilizers, antioxidants, polymers and organocatalysts. In addition, the synthesis, and applications of coordination complexes of these ligands have also been overviewed. The current review is a continuation of our previous efforts in this area, focusing on the recent advancements during the period 2017 to present.

This review encapsulates the recently designed acyl thioureas, and their crystal structures, metal complexes and various applications from 2017 to present, including pharmacological aspects, chemosensing and heterogenous catalysis.

Antimycobacterial and anti-inflammatory activities of thiourea derivatives focusing on treatment approaches for severe pulmonary tuberculosis

Tuberculosis (TB) remains a serious public health problem and one of the main concern is the emergence of multidrug-resistant and extensively resistant TB. Hyper-reactive patients develop inflammatory necrotic lung lesions that aggravate the pathology and facilitate transmission of mycobacteria. Treatment of severe TB is a major clinical challenge that has few effective solutions and patients face a poor prognosis, years of treatment and different adverse drug reactions. In this work, fifteen novel and thirty-one unusual thiourea derivatives were synthesized and evaluated in vitro for their antimycobacterial and anti-inflammatory potential and, in silico for ADMET parameters and for structure-activity relationship (SAR). Thioureas derivatives 10, 15, 16, 28 and 29 that had shown low cytotoxicity and high activities were selected for further investigation, after SAR study. These five thioureas derivatives inhibited Mtb H37Rv growth in bacterial culture and in infected macrophages, highlighting thiourea derivative 28 (MIC₅₀ 2.0 ± 1.1 and 2.3 ± 1.1 µM, respectively). Moreover, these compounds were active against the hypervirulent clinical Mtb strain M299, in bacterial culture, especially 16, 28 and 29, and in extracellular clumps, highlighting 29, with MIC₅₀ 5.6 ± 1.2 µM. Regarding inflammation, they inhibited NO through the suppression of iNOS expression, and also inhibited the production of TNF-α and IL-1β. In silico studies were carried out suggesting that these five compounds could be administered by oral route and have low toxicological effects when compared to rifampicin. In conclusion, our data show that, at least, thiourea derivatives 16, 28 and 29 are promising antimycobacterial and anti-inflammatory agents, and candidates for further prospective studies aiming new anti-TB drugs, that can be used on a dual approach for the treatment of severe TB cases associated with exacerbated inflammation.

Nanoparticles Loaded with a New Thiourea Derivative: Development and In vitro Evaluation Against Leishmania amazonensis

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by protozoa of the genus Leishmania. Current treatments are restricted to a small number of drugs that display both severe side effects and a potential for parasites to develop resistance. A new N-(3,4-methylenedioxyphenyl)-N'- (2-phenethyl) thiourea compound (thiourea 1) has shown promising in vitro activity against Leishmania amazonensis with an IC₅₀ of 54.14 μM for promastigotes and an IC₅₀ of 70 μM for amastigotes.

OBJECTIVE

To develop a formulation of thiourea 1 as an oral treatment for leishmaniasis, it was incorporated into Nanoparticles (NPs), a proven approach to provide long-acting drug delivery systems.

METHODS

Poly (D,L-Lactic-co-Glycolic Acid) (PLGA) polymeric NPs containing thiourea 1 were obtained through a nanoprecipitation methodology associated with solvent evaporation. The NPs containing thiourea 1 were characterized for Encapsulation Efficiency (EE%), reaction yield (% w/w), surface charge, particle size and morphology by Transmission Electron Microscopy (TEM).

RESULTS

NPs with thiourea 1 showed an improved in vitro leishmanicidal activity with a reduction in its cytotoxicity against macrophages (CC₅₀>100 μg/mL) while preserving its IC₅₀ against intracellular amastigotes (1.46 ± 0.09 μg/mL). This represents a parasite Selectivity Index (SI) of 68.49, which is a marked advancement from the reference drug pentamidine (SI = 30.14).

CONCLUSION

The results suggest that the incorporation into NPs potentiated the therapeutic effect of thiourea 1, most likely by improving the selective delivery of the drug to the phagocytic cells that are targeted for infection by L. amazonensis. This work reinforces the importance of nanotechnology in the acquisition of new therapeutic alternatives for oral treatments.

Unveiling the Targets Involved in the Quest of Antileishmanial Leads Using In silico Methods

BACKGROUND

Leishmaniasis is a neglected tropical disease associated with several clinical manifestations, including cutaneous, mucocutaneous, and visceral forms. As currently available drugs have some limitations (toxicity, resistance, among others), the target-based identification has been an important approach to develop new leads against leishmaniasis. The present study aims to identify targets involved in the pharmacological action of potent antileishmanial compounds.

METHODS

The literature information regarding molecular interactions of antileishmanial compounds studied over the past half-decade is discussed. The information was obtained from databases such as Wiley, SciFinder, Science Direct, National Library of Medicine, American Chemical Society, Scientific Electronic Library Online, Scopus, Springer, Google Scholar, Web of Science, etc. Results: Numerous in vitro antileishmanial compounds showed affinity and selective interactions with enzymes such as arginase, pteridine reductase 1, trypanothione reductase, pyruvate kinase, among others, which are crucial for the survival and virulence of the Leishmania parasite.

CONCLUSION

The in-silico activity of small molecules (enzymes, proteins, among others) might be used as pharmacological tools to develop candidate compounds for the treatment of leishmaniasis. As some pharmacologically active compounds may act on more than one target, additional studies of the mechanism (s) of action of potent antileishmanial compounds might help to better understand their pharmacological action. Also, the optimization of promising antileishmanial compounds might improve their biological activity.

Non-covalent interactions involving remote substituents influence the topologies of supramolecular chains featuring hydroxyl-O–H⋯O(hydroxyl) hydrogen bonding in crystals of (HOCH2CH2)2NC(S)N(H)(C6H4Y-4) for Y = H, Me, Cl and NO2

Secondary non-covalent interactions prove crucial in determining the topology of supramolecular chains sustained by conventional O–H⋯O hydrogen bonding.

In vitro evaluation of antitrypanosomal activity and molecular docking of benzoylthioureas

A series of sixteen benzoylthioureas derivatives were initially evaluated in vitro against the epimastigote form of Trypanosoma cruzi. All of the tested compounds inhibited the growth of this form of the parasite, and due to the promising anti-epimastigote activity from three of these compounds, they were also assayed against the trypomastigote and amastigote forms. ADMET-Tox in silico predictions and molecular docking studies with two main enzymatic targets (cruzain and CYP-51) were performed for the three compounds with the highest activity. The docking studies showed that these compounds can interact with the active site of cruzain by hydrogen bonds and can be coordinated with Fe-heme through the carbonyl oxygen atom of the CYP51. These findings can be considered an important starting point for the proposal of the benzoylthioureas as potent, selective, and multi-target antitrypanosomal agents.

A novel route to unsymmetrical disubstituted ureas and thioureas by HMPA catalyzed reductive alkylation with trichlorosilane

A HMPA catalyzed reductive alkylation of ureas and thioureas with trichlorosilane under mild reaction conditions has been developed.

Synthesis and Leishmanicidal Activity of Novel Urea, Thiourea, and Selenourea Derivatives of Diselenides

A novel series of thirty-one N-substituted urea, thiourea, and selenourea derivatives containing diphenyldiselenide entities were synthesized, fully characterized by spectroscopic and analytical methods, and screened for their in vitro leishmanicidal activities. The cytotoxic activity of these derivatives was tested against Leishmania infantum axenic amastigotes, and selectivity was assessed in human THP-1 cells. Thirteen of the synthesized compounds showed a significant antileishmanial activity, with 50% effective concentration (EC₅₀) values lower than that for the reference drug miltefosine (EC₅₀, 2.84 μM). In addition, the derivatives 9, 11, 42, and 47, with EC₅₀ between 1.1 and 1.95 μM, also displayed excellent selectivity (selectivity index ranged from 12.4 to 22.7) and were tested against infected macrophages. Compound 11, a derivative with a cyclohexyl chain, exhibited the highest activity against intracellular amastigotes, with EC₅₀ values similar to those observed for the standard drug edelfosine. Structure-activity relationship analyses revealed that N-aliphatic substitution in urea and selenourea is recommended for the leishmanicidal activity of these analogs. Preliminary studies of the mechanism of action for the hit compounds was carried out by measuring their ability to inhibit trypanothione reductase. Even though the obtained results suggest that this enzyme is not the target for most of these derivatives, their activity comparable to that of the standards and lack of toxicity in THP-1 cells highlight the potential of these compounds to be optimized for leishmaniasis treatment.