Benzimidazole derivatives endowed with potent antileishmanial activity

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

Synthesis, antileishmanial, antimalarial evaluation and molecular docking study of some hydrazine-coupled pyrazole derivatives

Pyrazole-bearing compounds are known for their diverse pharmacological effects including potent antileishmanial and antimalarial activities. Herein, some hydrazine-coupled pyrazoles were successfully synthesized and their structures were verified by employing elemental microanalysis, FTIR, and 1H NMR techniques. The in vitro antileishmanial and in vivo antimalarial activities of the synthesized pyrazole derivatives (9-15) were evaluated against Leishmania aethiopica clinical isolate and Plasmodium berghei infected mice, respectively. The result revealed that compound 13 displayed superior antipromastigote activity (IC50 = 0.018) that was 174- and 2.6-fold more active than the standard drugs miltefosine (IC50 = 3.130) and amphotericin B deoxycholate (IC50 = 0.047). The molecular docking study conducted on Lm-PTR1, complexed with Trimethoprim was acquired from the Protein Data Bank (PDB ID:2bfm), justified the better antileishmanial activity of compound 13. Furthermore, the target compounds 14 and 15 elicited better inhibition effects against Plasmodium berghei with 70.2% and 90.4% suppression, respectively. In conclusion, the hydrazine-coupled pyrazole derivatives may be considered potential pharmacophores for the preparation of safe and effective antileishmanial and antimalarial agents.

A Critical Review on Therapeutic Potential of Benzimidazole Derivatives: A Privileged Scaffold

Benzimidazole nucleus is a predominant heterocycle displaying a wide spectrum of pharmacological activities. The privileged nature of the benzimidazole scaffold has been revealed by its presence in most small molecule drugs and in its ability to bind multiple receptors with high affinity. A literature review of the scaffold reveals several instances where structural modifications of the benzimidazole core have resulted in high-affinity lead compounds against a variety of biological targets. Hence, this structural moiety offers opportunities to discover novel, better, safe and highly potent biological agents. The goal of the present review is to compile the medicinal properties of benzimidazole derivatives with a focus on SAR (Structure-Activity Relationships).

State-of-the-art Review on the Antiparasitic Activity of Benzimidazolebased Derivatives: Facing Malaria, Leishmaniasis, and Trypanosomiasis

Protozoan parasites represent a significant risk for public health worldwide, afflicting particularly people in more vulnerable categories and cause large morbidity and heavy economic impact. Traditional drugs are limited by their toxicity, low efficacy, route of administration, and cost, reflecting their low priority in global health management. Moreover, the drug resistance phenomenon threatens the positive therapy outcome. This scenario claims the need of addressing more adequate therapies. Among the diverse strategies implemented, the medicinal chemistry efforts have also focused their attention on the benzimidazole nucleus as a promising pharmacophore for the generation of new drug candidates. Hence, the present review provides a global insight into recent progress in benzimidazole-based derivatives drug discovery against important protozoan diseases, such as malaria, leishmaniasis and trypanosomiasis. The more relevant chemical features and structure-activity relationship studies of these molecules are discussed for the purpose of paving the way towards the development of more viable drugs for the treatment of these parasitic infections.

Spiro heterocycles bearing piperidine moiety as potential scaffold for antileishmanial activity: synthesis, biological evaluation, and in silico studies

New spiro-piperidine derivatives were synthesised via the eco-friendly ionic liquids in a one-pot fashion. The in vitro antileishmanial activity against Leishmania major promastigote and amastigote forms highlighted promising antileishmanial activity for most of the derivatives, with superior activity compared to miltefosine. The most active compounds 8a and 9a exhibited sub-micromolar range of activity, with IC50 values of 0.89 µM and 0.50 µM, respectively, compared to 8.08 µM of miltefosine. Furthermore, the antileishmanial activity reversal of these compounds via folic and folinic acids displayed comparable results to the positive control trimethoprim. This emphasises that their antileishmanial activity is through the antifolate mechanism via targeting DHFR and PTR1. The most active compounds showed superior selectivity and safety profile compared to miltefosine against VERO cells. Moreover, the docking experiments of 8a and 9a against Lm-PTR1 rationalised the observed in vitro activities. Molecular dynamics simulations confirmed a stable and high potential binding to Lm-PTR1.

Tetrahydrobenzo[h]quinoline derivatives as a novel chemotype for dual antileishmanial-antimalarial activity graced with antitubercular activity: Design, synthesis and biological evaluation

Derivatives with tetrahydrobenzo[h]quinoline chemotype were synthesized via one-pot reactions and evaluated for their antileishmanial, antimalarial and antitubercular activities. Based on a structure-guided approach, they were designed to possess antileishmanial activity through antifolate mechanism, via targeting Leishmania major pteridine reductase 1 (Lm-PTR1). The in vitro antipromastigote and antiamastigote activity are promising for all candidates and superior to the reference miltefosine, in a low or sub micromolar range of activity. Their antifolate mechanism was confirmed via the ability of folic and folinic acids to reverse the antileishmanial activity of these compounds, comparably to Lm-PTR1 inhibitor trimethoprim. Molecular dynamics simulations confirmed a stable and high potential binding of the most active candidates against leishmanial PTR1. For the antimalarial activity, most of the compounds exhibited promising antiplasmodial effect against P. berghei with suppression percentage of up to 97.78%. The most active compounds were further screened in vitro against the chloroquine resistant strain P. falciparum, (RKL9) and showed IC50 value range of 0.0198-0.096 μM, compared to IC50 value of 0.19420 μM for chloroquine sulphate. Molecular docking of the most active compounds against the wild-type and quadruple mutant pf DHFR-TS structures rationalized the in vitro antimalarial activity. Some candidates showed good antitubercular activity against sensitive Mycobacterium tuberculosis in a low micromolar range of MIC, compared to 0.875 μM of isoniazid. The top active ones were further tested against a multidrug-resistant strain (MDR) and extensively drug-resistant strain (XDR) of Mycobacterium tuberculosis. Interestingly, the in vitro cytotoxicity test of the best candidates displayed high selectivity indices emphasizing their safety on mammalian cells. Generally, this work introduces a fruitful matrix for new dual acting antileishmanial-antimalarial chemotype graced with antitubercular activity. This would help in tackling drug-resistance issues in treating some Neglected Tropical Diseases.

Virtual Screening of Benzimidazole Derivatives as Potential Triose Phosphate Isomerase Inhibitors with Biological Activity against Leishmania mexicana

Leishmania mexicana (L. mexicana) is a causal agent of cutaneous leishmaniasis (CL), a “Neglected disease”, for which the search for new drugs is a priority. Benzimidazole is a scaffold used to develop antiparasitic drugs; therefore, it is interesting molecule against L. mexicana. In this work, a ligand-based virtual screening (LBVS) of the ZINC15 database was performed. Subsequently, molecular docking was used to predict the compounds with potential binding at the dimer interface of triosephosphate isomerase (TIM) of L. mexicana (LmTIM). Compounds were selected on binding patterns, cost, and commercial availability for in vitro assays against L. mexicana blood promastigotes. The compounds were analyzed by molecular dynamics simulation on LmTIM and its homologous human TIM. Finally, the physicochemical and pharmacokinetic properties were determined in silico. A total of 175 molecules with docking scores between −10.8 and −9.0 Kcal/mol were obtained. Compound E2 showed the best leishmanicidal activity (IC50 = 4.04 µM) with a value similar to the reference drug pentamidine (IC50 = 2.23 µM). Molecular dynamics analysis predicted low affinity for human TIM. Furthermore, the pharmacokinetic and toxicological properties of the compounds were suitable for developing new leishmanicidal agents.

In Vitro Determination of Antileshmanial Activities of Benzimidazolium Derivatives on L. major Promastigotes and Amastigotes

PURPOSE

Leishmaniasis is a serious public health problem infecting millions of people worldwide. An effective and reliable treatment method to be used in the treatment of the disease has not been developed yet.

METHODS

In this article, the anti-leishmanial activities of two benzimidazolium derivatives (B.A and B.B) against Leishmania major promastigotes and amastigotes, which are known to cause cutaneous leishmaniasis, were investigated for the first time. The immunostimulatory activity of the developed formulations was determined using the J774 murine macrophage cell line.

RESULTS

B.A and B.B compounds were found to have a much higher cytotoxic effect than Amphotericin B (IC₅₀ value 0.75 μM ± 0.03), which is used as the reference drug. The IC₅₀ value was determined as 2.02 µM ± 0.52 for B.A and 1.83 µM ± 0.71 for B.B in Leishmania promastigotes. In addition, IC₅₀ values of B. A and B.B Leishmania amastigotes were found to be 1.01 µM and 0.67 µM, respectively. It was found that B.B was 81.12 times more selective than Amphotericin B and showed the highest selectivity against L. major promastigotes (359.09) and amastigotes (980.80). Considering the selectivity indices (SI) of B.A and B.B, both compounds tested are more promising than Amphotericin B.

CONCLUSION

The results showed that benzimidazolium derivatives have anti-leishmanial potential against L. major, which is the causative agent of cutaneous leishmaniasis. Thus, we can say that the obtained results will help the development of effective and safe antileishmanial drug formulations against cutaneous leishmaniasis.

Synthesis, Molecular Docking, and Bioactivity Study of Novel Hybrid Benzimidazole Urea Derivatives: A Promising α-Amylase and α-Glucosidase Inhibitor Candidate with Antioxidant Activity

A novel series of benzimidazole ureas 3a-h were elaborated using 2-(1H-benzoimidazol-2-yl) aniline 1 and the appropriate isocyanates 2a-h. The antioxidant and possible antidiabetic activities of the target benzimidazole-ureas 3a-h were evaluated. Almost all compounds 3a-h displayed strong to moderate antioxidant activities. When tested using the three antioxidant techniques, TAC, FRAP, and MCA, compounds 3b and 3c exhibited marked activity. The most active antioxidant compound in this family was compound 3g, which had excellent activity using four different methods: TAC, FRAP, DPPH-SA, and MCA. In vitro antidiabetic assays against α-amylase and α-glucosidase enzymes revealed that the majority of the compounds tested had good to moderate activity. The most favorable results were obtained with compounds 3c, 3e, and 3g, and analysis revealed that compounds 3c (IC₅₀ = 18.65 ± 0.23 μM), 3e (IC₅₀ = 20.7 ± 0.06 μM), and 3g (IC₅₀ = 22.33 ± 0.12 μM) had good α-amylase inhibitory potential comparable to standard acarbose (IC₅₀ = 14.21 ± 0.06 μM). Furthermore, the inhibitory effect of 3c (IC₅₀ = 17.47 ± 0.03 μM), 3e (IC₅₀ = 21.97 ± 0.19 μM), and 3g (IC₅₀ = 23.01 ± 0.12 μM) on α-glucosidase was also comparable to acarbose (IC₅₀ = 15.41 ± 0.32 μM). According to in silico molecular docking studies, compounds 3a-h had considerable affinity for the active sites of human lysosomal acid α-glucosidase (HLAG) and pancreatic α-amylase (HPA), indicating that the majority of the examined compounds had potential anti-hyperglycemic action.

New antileishmanial quinoline linked isatin derivatives targeting DHFR-TS and PTR1: Design, synthesis, and molecular modeling studies

In a search for new drug candidates for one of the neglected tropical diseases, leishmaniasis, twenty quinoline-isatin hybrids were synthesized and tested for their in vitro antileishmanial activity against Leishmaniamajor strain. All the synthesized compounds showed promising in vitro activity against the promastigote form in a low micromolar range (IC₅₀ = 0.5084-5.9486 μM) superior to the reference miltefosine (IC₅₀ = 7.8976 μM). All the target compounds were then tested against the intracellular amastigote form and showed promising inhibition effects (IC₅₀ = 0.60442-8.2948 μM versus 8.08 μM for miltefosine). Compounds 4e, 4b and 4f were shown to possess the highest antileishmanial activity against both promastigote and amastigote forms. The most active compounds were proven to exhibit their significant antileishmanial effects through antifolate mechanism, targeting DHFR-TS and PTR1. To evaluate the safety profile of the most active derivatives 4e, 4b and 4f, the in vitro cytotoxicity test was carried out and displayed higher selectivity indices than the reference miltefosine. Molecular docking within putative target protein PTR1 confirmed the high potentiality of the most active compounds 4e, 4b and 4f to block the catalytic activity of Lm-PTR1.

Evaluation of ferrocenyl-containing γ-hydroxy-γ-lactam-derived tetramates as potential antiplasmodials

A series of ferrocenyl-containing γ-hydroxy-γ-lactam tetramates were prepared in 2-3 steps through ring opening-ring closure (RORC) process of γ-ylidene-tetronate derivatives in the presence of ferrocenyl alkylamines. The compounds were screened in vitro for their antiplasmodial activity against chloroquine-sensitive (3D7) and chloroquine-resistant (W2) clones of P. falciparum, displaying activity in the range of 0.12-100 μM, with generally good resistance index. The most active ferrocene in these series exhibited IC₅₀ equal to 0.09 μM (3D7) and 0.12 μM (W2). The low cytotoxicity of the ferrocenyl-containing γ-hydroxy-γ-lactam tetramates against Human Umbilical Vein Endothelial (HUVEC) cell line demonstrated selective antiparasitic activity. The redox properties of these ferrocene-derived tetramates were studied and physico-biochemical studies evidenced that these derivatives can exert potent antimalarial activities via a mechanism distinct from ferroquine.

Iridium/f-diaphos catalyzed asymmetric hydrogenation of 2-imidazolyl aryl/alkyl ketones

The iridium/f-diaphos L1, L5 or L12 catalyzed asymmetric hydrogenation of 2-imidazolyl aryl/alkyl ketones to afford two enantiomers of the desired chiral alcohols with high conversions (up to 99% yield) and moderate to excellent enantioselectivities (61% - >99% ee) was realized for the first time. This protocol could be easily conducted on a gram-scale with a TON of 9700.

A Comprehensive Account on Recent Progress in Pharmacological Activities of Benzimidazole Derivatives

Nowadays, nitrogenous heterocyclic molecules have attracted a great deal of interest among medicinal chemists. Among these potential heterocyclic drugs, benzimidazole scaffolds are considerably prevalent. Due to their isostructural pharmacophore of naturally occurring active biomolecules, benzimidazole derivatives have significant importance as chemotherapeutic agents in diverse clinical conditions. Researchers have synthesized plenty of benzimidazole derivatives in the last decades, amidst a large share of these compounds exerted excellent bioactivity against many ailments with outstanding bioavailability, safety, and stability profiles. In this comprehensive review, we have summarized the bioactivity of the benzimidazole derivatives reported in recent literature (2012-2021) with their available structure-activity relationship. Compounds bearing benzimidazole nucleus possess broad-spectrum pharmacological properties ranging from common antibacterial effects to the world's most virulent diseases. Several promising therapeutic candidates are undergoing human trials, and some of these are going to be approved for clinical use. However, notable challenges, such as drug resistance, costly and tedious synthetic methods, little structural information of receptors, lack of advanced software, and so on, are still viable to be overcome for further research.

Some Scaffolds as Anti-leishmanial Agents: An Review

Leishmaniasis is a parasitic infectious neglected tropical disease transmitted to humans by the parasites of Leishmania species. Mainly three types of leishmaniasis cases such as visceral (VL), cutaneous (CL) and mucocutaneous leishmaniasis are usually observed. In many western countries, almost 700,000 to 1million peoples are suffering from leishmaniasis and it is estimated that around 26000 to 65000 deaths occurs annually. For its treatment few drugs are available however none of them are ideal to treat leishmaniasis due to long treatment, discomfort mode of administration, risk of high level toxicity, high resistance against etc. Hence so many patients are unable to take complete treatment due to the high drug resistance. The present review will focus on antileishmanial activity of reported derivatives of betacarboline, chalcone, azole, quinoline, quinazoline, benzimidazole, benzadiazapine, thiaazoles, semicarbazone and hydontoin analogues. We believe that this present study will helpful to researcher to design new antileishmanial agents.

New C2- and N3-Modified Thieno[2,3-d]Pyrimidine Conjugates with Cytotoxicity in the Nanomolar Range

AIMS

The aim of the current study was to develop and explore a series of new cytotoxic agents based on the conjugation between the thieno[2,3-d]pyrimidine moiety and a second pharmacophore at the C2 or N3 position.

BACKGROUND

As the thieno[2,3-d]pyrimidine core is a bioisostere of the 4-anilinoquinazoline, various new thienopyrimidine derivatives were synthesized by modifying the structure of the clinically used anticancer quinazoline EGFR inhibitors of the first generation - gefitinib, and second generation - dacomitinib and canertinib. It was reported that some thieno[2,3-d]pyrimidine derivatives showed improved EGFR inhibitory activity. On the other hand, the benzimidazole heterocycle is present as a pharmacophore unit in the structure of many clinically used chemotherapeutic agents. Some 2-aminobenzimidazole derivatives, possessing anticancer activity, demonstrated EGFR inhibition and the benzimidazole derivative EGF816 is currently in the second phase of clinical trials.

OBJECTIVE

The objectives of the study were design of a novel series thieno[2,3-d]pyrimidines, synthesis of the compounds and investigation of their effects towards human cancer HT-29, MDA-MB-231, HeLa, HepG2 and to normal human Lep3 cell lines. (American Type Culture Collection, ATCC, Rockville, MD, USA) Methods: The synthetic protocol implemented cyclocondensation of 2-amino-thiophenes and nitriles in inert medium, aza-Michael addition to benzimidazole derivatives and nucleophylic substitution at the N3 place. MTS test was used in order to establish the cytotoxicity of the tested compounds. SAR analysis and in silico assessment of the inhibitory potential towards human oncogenic V^599EB-Raf were performed using Molinspiration tool and Molecular Operating environment software.

RESULTS

The MTS test data showed that almost all studied thieno[2,3-d]pyirimidines (9-13, 21-22 and 25) manifest high inhibiting effect on the cell proliferation at nanomolar concentrations, whereat compounds 9 (IC₅₀ = 130 nM) and 10 (IC₅₀ = 261 nM) containing amino acid moiety, and 21 (IC₅₀ = 108 nM) possesing two thienopyrimidine moieties attached to a 1,3-disubstituted benzimidazole linker, revealed many times lower toxicity against Lep3 cells compared to the cancer cells. Thienopyrimidines 11-13 possessed high selectivity against HeLa cells. Compound 13 showed high inhibitory activity against MDA-MB-231 and HepG2, with IC50 1.44 nM and 1.11 nM respectively. To outline the possible biological target of the studied coumpounds, their potential to interact with human oncogenic V^599EB-Raf was explored by a docking study. As a result, it was suggested that the benzimidazolyl and glycyl fragments could enhance the binding ability of the new compounds by increasing the number of hydrogen bond acceptors and by stabilizing the inactive form of the enzyme.

CONCLUSION

The thienopyrimidines tested in vitro towards human cancer HT-29, MDA-MB-231, HeLa, HepG2 and normal human Lep3 cell lines demonstrated cytotoxicity in nanomolar range. It was established that compounds 9, 10 and 21 showed many times lower toxicity against normal Lep3 cells that can provide a high selectivity towards all four cancer cell lines at small concentrations. Based on the analysis of the structure-activity relationship, the observed trends in the cytotoxicity could be related to the lipophilicity and the topological polar surface area of the tested compounds. The docking study on the potential of the new thieno[2,3-d]pyrimidine-4-ones to interact with mutant V^599EB-Raf showed that the compounds might be able to stabilize the enzyme in its inactive form.

A facile approach synthesis of benzoylaryl benzimidazole as potential α-amylase and α-glucosidase inhibitor with antioxidant activity

Synthetic routes to a series of benzoylarylbenzimidazol 3a-h have been derived from 3,4-diaminobenzophenone and an appropriate arylaldehyde in the presence of ammonium chloride or a mixture of ammonium chloride and sodium metabisulfite as catalyst. The antioxidant activity of targeted compounds 3a-h has been measured by four different methods and the overall antioxidant evaluation of the compounds indicated the significant MCA, FRAP, and (DPPH-SA) of the compounds except for the compound 3h. In vitro antidiabetic assay of α-amylase and α-glucosidase suggest a good to excellent activity for most tested compounds. The target benzimidazole 3f containing hydroxyl motif at para-position of phenyl revealed an important activity inhibitor against α- amylase (IC₅₀ = 12.09 ± 0.38 µM) and α-glucosidase (IC₅₀ = 11.02 ± 0.04 µM) comparable to the reference drug acarbose. The results of the anti hyperglycemic activity were supported by means of in silico molecular docking calculations showing strong binding affinity of compounds 3a-h with human pancreatic α-amylase (HPA) and human lysosomal acid-α-glucosidase (HLAG) active sites that confirm a good to excellent activity for most of tested compounds.

Design, Synthesis and In Vitro Investigation of Novel Basic Celastrol Carboxamides as Bio-Inspired Leishmanicidal Agents Endowed with Inhibitory Activity against Leishmania Hsp90

The natural triterpene celastrol (CE) is here used as lead compound for the design and synthesis of a panel of eleven CE carboxamides that were tested in vitro for their growth inhibitory activity against Leishmania infantum and L.tropica parasites. Among them, in vitro screening identified four basic CE carboxamides endowed with nanomolar leishmanicidal activity, against both the promastigotes and the intramacrophage Leishmania amastigotes forms. These compounds also showed low toxicity toward two human (HMEC-1 and THP-1) and one murine (BMDM) cell lines. Interestingly, the most selective CE analogue (compound 3) was also endowed with the ability to inhibit the ATPase activity of the Leishmania protein chaperone Hsp90 as demonstrated by the in vitro assay conducted on a purified, full-length recombinant protein. Preliminary investigations by comparing it with the naturally occurring Hsp90 active site inhibitor Geldanamycin (GA) in two different in vitro experiments were performed. These promising results set the basis for a future biochemical investigation of the mode of interaction of celastrol and CE-inspired compounds with Leishmania Hsp90.

Quinolizidine-Derived Lucanthone and Amitriptyline Analogues Endowed with Potent Antileishmanial Activity

Leishmaniases are neglected diseases that are endemic in many tropical and sub-tropical Countries. Therapy is based on different classes of drugs which are burdened by severe side effects, occurrence of resistance and high costs, thereby creating the need for more efficacious, safer and inexpensive drugs. Herein, sixteen 9-thioxanthenone derivatives (lucanthone analogues) and four compounds embodying the diarylethene substructure of amitriptyline (amitriptyline analogues) were tested in vitro for activity against Leishmania tropica and L. infantum promastigotes. All compounds were characterized by the presence of a bulky quinolizidinylalkyl moiety. All compounds displayed activity against both species of Leishmania with IC₅₀ values in the low micromolar range, resulting in several fold more potency than miltefosine, comparable to that of lucanthone, and endowed with substantially lower cytotoxicity to Vero-76 cells, for the best of them. Thus, 4-amino-1-(quinolizidinylethyl)aminothioxanthen-9-one (14) and 9-(quinolizidinylmethylidene)fluorene (17), with selectivity index (SI) in the range 16-24, represent promising leads for the development of improved antileishmanial agents. These two compounds also exhibited comparable activity against intramacrophagic amastigotes of L. infantum. Docking studies have suggested that the inhibition of trypanothione reductase (TryR) may be at the basis (eventually besides other mechanisms) of the observed antileishmanial activity. Therefore, these investigated derivatives may deserve further structural improvements and more in-depth biological studies of their mechanisms of action in order to develop more efficient antiparasitic agents.

Multiscale Process Modelling in Translational Systems Biology of Leishmania major: A Holistic view

Present work aims to utilize systems biology and molecular modelling approach to understand the inhibition kinetics of Leishmania major GLO I and identifying potential hit followed by their validation through in vitro and animal studies. Simulation of GLO I inhibition has shown to affect reaction fluxes of almost all reactions in the model that led to increased production of various AGEs and free radicals. Further, in vitro testing of C1 and C2, selected through molecular modelling revealed remarkable morphological alterations like size reduction, membrane blebbing and loss in motility of the parasite, however, only C1 showed better antileishmanial activity. Additionally, C1 showed apoptosis mediated leishmanicidal activity (apoptosis-like cell death) along with cell-cycle arrest at sub-G0/G1 phase and exhibited potent anti-leishmanial effect against intracellular amastigotes. Furthermore, decrease in parasite load was also observed in C1 treated BALB/c female mice. Our results indicate that C1 has healing effect in infected mice and effectively reduced the parasitic burden. Hence, we suggest C1 as a lead molecule which on further modification, may be used to develop novel therapeutics against Leishmaniasis.

Structure based designing of benzimidazole/benzoxazole derivatives as anti-leishmanial agents

Folates are essential biomolecules required to carry out many crucial processes in leishmania parasite. Dihydrofolate reductase-thymidylate synthase (DHFR-TS) and pteridine reductase 1 (PTR1) involved in folate biosynthesis in leishmania have been established as suitable targets for development of chemotherapy against leishmaniasis. In the present study, various computational tools such as homology modelling, pharmacophore modelling, docking, molecular dynamics and molecular mechanics have been employed to design dual DHFR-TS and PTR1 inhibitors. Two designed molecules, i.e. 2-(4-((4-nitrobenzyl)oxy)phenyl)-1H-benzo[d]imidazole and 2-(4-((2,4-dichlorobenzyl)oxy)phenyl)-1H-benzo[d]oxazolemolecules were synthesized. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay was performed to evaluate in vitro activity of molecules against promastigote form of Leishmania donovani using Miltefosine as standard. 2-(4-((4-nitrobenzyl)oxy)phenyl)-1H-benzo[d]imidazole and 2-(4-((2,4-dichlorobenzyl)oxy)phenyl)-1H-benzo[d]oxazolemolecules were found to be moderately active with showed IC₅₀ = 68 ± 2.8 µM and 57 ± 4.2 µM, respectively.

Homology Modelling and Molecular Docking Studies of Selected Substituted Benzo[d]imidazol-1-yl)methyl)benzimidamide Scaffolds on Plasmodium falciparum Adenylosuccinate Lyase Receptor

Plasmodium falciparum adenylosuccinate lyase (PfADSL) is an important enzyme in purine metabolism. Although several benzimidazole derivatives have been commercially developed into drugs, the template design as inhibitor against PfADSL has not been fully explored. This study aims to model the 3-dimensional (3D) structure of PfADSL, design and predict in silico absorption, distribution, metabolism, excretion and toxicity (ADMET) of 8 substituted benzo[d]imidazol-1-yl)methyl)benzimidamide compounds as well as predict the potential interaction modes and binding affinities of the designed ligands with the modelled PfADSL. PfADSL 3D structure was modelled using SWISS-MODEL, whereas the compounds were designed using ChemDraw Professional. ADMET predictions were done using OSIRIS Property Explorer and Swiss ADME, whereas molecular docking was done with AutoDock Tools. All designed compounds exhibited good in silico ADMET properties, hence can be considered safe for drug development. Binding energies ranged from -6.85 to -8.75 kcal/mol. Thus, they could be further synthesised and developed into active commercial antimalarial drugs.

Synthesis, in vitro biological evaluation and in silico studies of certain arylnicotinic acids conjugated with aryl (thio)semicarbazides as a novel class of anti-leishmanial agents

Herein we introduce new compounds as conjugates of arylnicotinic acids with aryl (thio)semicarbazide derivatives. Based on a structure-guided approach, they were designed to possess anti-leishmanial activity through anti-folate mechanism, via targeting Leishmania major pteridine reductase 1 (Lm-PTR1). The in vitro anti-promastigote and anti-amastigote activity were promising for many thiosemicarbazide derivatives and superior to the reference miltefosine. The most active compounds 8i and 8j exhibited their anti-amastigote activity with IC₅₀ values of 4.2 and 3.3 μM, respectively, compared to reference miltefosine (IC₅₀ value of 7.3). Their anti-folate mechanism was confirmed via the ability of folic and folinic acids to reverse the anti-leishmanial activity of these compounds, comparably to Lm-PTR1 inhibitor trimethoprim. Interestingly, the in vitro cytotoxicity test of the most active compounds displayed higher selectivity indices than that of miltefosine emphasizing their safety on mammalian cells. Furthermore, the docking experiments on Lm-PTR1 as a putative target rationalized the in vitro anti-leishmanial activity. The in silico predictions exhibited promising pharmacokinetics and drug-likeness profiles of the most active compounds. Generally, this work introduces a fruitful matrix for new anti-leishmanial chemotype which would extend the chemical space for the anti-leishmanial activity.