Novel benzimidazole-acrylonitrile hybrids and their derivatives: Design, synthesis and antimycobacterial activity

Recent advancements in the quest of benzazoles as anti-Mycobacterium tuberculosis agents

Tuberculosis (TB) remains a global health challenge, claiming numerous lives each year, despite recent advancements in drug discovery and treatment strategies. Current TB treatment typically involves long-duration chemotherapy regimens that are often accompanied by adverse effects. The introduction of new anti-TB drugs, such as Bedaquiline, Delamanid, and Pretomanid, offers hope for more effective treatment, although challenges persist keeping the quest to find new anti-TB chemotypes an incessant exercise of medicinal chemists. Towards this initiative, the benzazoles continue to draw attention and have been recognised as new anti-TB scaffolds. Benzazole-containing compounds emerged as new chemotypes with potential to offer a versatile platform for new anti-TB drug design to generate new leads for further optimization. The elucidation of their chemical properties, biological effects, and potential mechanisms of action, would lead to identify innovative candidates for TB therapy. As medicinal chemists delve deeper into the SARs and mechanisms of action of benzazole derivatives, new opportunities for creating effective and safe anti-TB medications arise. This review highlights the potential impact of benzazole-based compounds on the search for new therapeutic agents against tuberculosis, emphasizing the importance of continued research and innovation in the field.

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).

Indole-Acrylonitrile Derivatives as Potential Antitumor and Antimicrobial Agents-Synthesis, In Vitro and In Silico Studies

A series of 2-(1H-indol-2-yl)-3-acrylonitrile derivatives, 2a-x, 3, 4a-b, 5a-d, 6a-b, and 7, were synthesized as potential antitumor and antimicrobial agents. The structures of the prepared compounds were evaluated based on elemental analysis, IR, ¹H- and ¹³NMR, as well as MS spectra. X-ray crystal analysis of the representative 2-(1H-indol-2-yl)-3-acrylonitrile 2l showed that the acrylonitrile double bond was Z-configured. All compounds were screened at the National Cancer Institute (USA) for their activities against a panel of approximately 60 human tumor cell lines and the relationship between structure and in vitro antitumor activity is discussed. Compounds of interest 2l and 5a-d showed significant growth inhibition potency against various tumor cell lines with the mean midpoint GI₅₀ values of all tests in the range of 0.38-7.91 μM. The prominent compound with remarkable activity (GI₅₀ = 0.0244-5.06 μM) and high potency (TGI = 0.0866-0.938 μM) against some cell lines of leukemia (HL-60(TB)), non-small cell lung cancer (NCI-H522), colon cancer (COLO 205), CNS cancer (SF-539, SNB-75), ovarian cancer ((OVCAR-3), renal cancer (A498, RXF 393), and breast cancer (MDA-MB-468) was 3-[4-(dimethylamino)phenyl]-2-(1-methyl-1H-indol-2-yl)acrylonitrile (5c). Moreover, the selected 2-(1H-indol-2-yl)-3-acrylonitriles 2a-c and 2e-x were evaluated for their antibacterial and antifungal activities against Gram-positive and Gram-negative pathogens as well as Candida albicans. Among them, 2-(1H-indol-2-yl)-3-(1H-pyrrol-2-yl)acrylonitrile (2x) showed the most potent antimicrobial activity and therefore it can be considered as a lead structure for further development of antimicrobial agents. Finally, molecular docking studies as well as drug-likeness and ADME profile prediction were carried out.

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.

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.

Aryl acrylonitriles synthesis enabled by palladium-catalyzed α-alkenylation of arylacetonitriles with vinyl halides/triflates

Aryl acrylonitriles are an important subclass of acrylonitriles in the medicinal chemistry and pharmaceutical industry. Herein, an efficient synthesis of aryl acrylonitrile derivatives using a Palladium/NIXANTPHOS-based catalyst system was developed. This approach furnishes a variety of substituted and functionalized aryl acrylonitriles (up to 95% yield). The scalability of the transformation and the synthetic versatility of aryl acrylonitrile were demonstrated.

Targeting Non-Replicating Mycobacterium tuberculosis and Latent Infection: Alternatives and Perspectives (Mini-Review)

Latent tuberculosis infection (LTBI) represents a major challenge to curing TB disease. Current guidelines for LTBI management include only three older drugs and their combinations-isoniazid and rifamycins (rifampicin and rifapentine). These available control strategies have little impact on latent TB elimination, and new specific therapeutics are urgently needed. In the present mini-review, we highlight some of the alternatives that may potentially be included in LTBI treatment recommendations and a list of early-stage prospective small molecules that act on drug targets specific for Mycobacterium tuberculosis latency.

Insights into the chemistry and therapeutic potential of acrylonitrile derivatives

Acrylonitrile is a fascinating scaffold widely found in many natural products, drugs, and drug candidates with various biological activities. Several drug molecules such as entacapone, rilpivirine, teriflunomide, and so forth, bearing an acrylonitrile moiety have been marketed. In this review, diverse synthetic strategies for constructing desired acrylonitriles are discussed, and the different biological activities and medicinal significance of various acrylonitrile derivatives are critically evaluated. The information gathered is expected to provide rational guidance for the development of clinically useful agents from acrylonitriles.

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.

Screening and Identification of a Novel Anti-tuberculosis Compound That Targets Deoxyuridine 5'-Triphosphate Nucleotidohydrolase

Tuberculosis (TB) is still a threat to humans worldwide. The rise of drug-resistant TB strains has escalated the need for developing effective anti-TB agents. Deoxyuridine 5′-triphosphate nucleotidohydrolase (dUTPase) is essential for thymidylate biosynthesis to maintain the DNA integrity. In Mycobacterium tuberculosis, dUTPase provides the sole source for thymidylate biosynthesis, which also has the specific five-residue loop and the binding pockets absent in human dUTPase. Therefore, dUTPase has been regarded as a promising anti-TB drug target. Herein, we used a luminescence-based dUTPase assay to search for the inhibitors target M. tuberculosis dUTPase (Mt-dUTPase) and identified compound F0414 as a potent Mt-dUTPase inhibitor with an IC₅₀ of 0.80 ± 0.09 μM. F0414 exhibited anti-TB activity with low cytotoxicity. Molecular docking model and site-directed mutation experiments revealed that P79 was the key residue in the interaction of Mt-dUTPase and F0414. Moreover, F0414 was shown to have stronger binding with Mt-dUTPase than with Mt-P79A-dUTPase by surface plasmon resonance (SPR) detection. Interestingly, F0414 exhibited insensitivity and weak directly binding on human dUTPase compared with that on Mt-dUTPase. All the results highlight that F0414 is the first compound reported to have anti-TB activity by inhibiting Mt-dUTPase, which indicates the potential application in anti-TB therapy.

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.

Acrylonitrile Derivatives against Trypanosoma cruzi: In Vitro Activity and Programmed Cell Death Study

The neglected infection known as Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, results in more than 7000 deaths per year, with an increasing number of cases in non-endemic areas such as Europe or the United States. Moreover, with the current available therapy, only two compounds which are active against the acute phase of the disease are readily available. In addition, these therapeutic agents display multiple undesired side effects such as high toxicity, they are expensive, the treatment is lengthy and the resistant strain has emerged. Therefore, there is a need to find new compounds against Chagas disease which should be active against the parasite but also cause low toxicity to the patients. In the present work, the activity of novel acrylonitriles against Trypanosoma cruzi was evaluated as well as the analysis of the physiological events induced in the treated parasites related to the cell death process. Hence, the characteristic features of an apoptosis-like process such as chromatin condensation and mitochondrial membrane potential, among others, were studied. From the 32 compounds tested against the epimastigote stage of T. cruzi, 11 were selected based on their selectivity index to determine if these compounds were able to induce programmed cell death (PCD) in the treated parasites. Furthermore, acrylonitriles Q5, Q7, Q19, Q27 and Q29 were shown to trigger physiological events related in the PCD. Therefore, this study highlights the therapeutic potential of acrylonitriles as novel trypanocidal agents.

Hybridization Approach to Drug Discovery Inhibiting Mycobacterium tuberculosis-An Overview

Tuberculosis is one of the top 10 causes of death worldwide and the leading cause of death from a single infectious agent, mainly due to Mycobacterium tuberculosis (MTB). Recently, clinical prognoses have worsened due to the emergence of multi-drug resistant (MDR) and extensive-drug resistant (XDR) tuberculosis, which lead to the need for new, efficient and safe drugs. Among the several strategies, polypharmacology could be considered one of the best solutions, in particular, the multitarget directed ligands strategy (MTDLs), based on the synthesis of hybrid ligands acting against two targets of the pathogen. The framework strategy comprises linking, fusing and merging approaches to develop new chemical entities. With these premises, this review aims to provide an overview of the recent hybridization approach, in medicinal chemistry, of the most recent and promising multitargeting antimycobacterial candidates.

Recent advancements on Benzimidazole: A versatile scaffold in medicinal chemistry

Benzimidazole is nitrogen containing fused heterocycle which has been extensively explored in medicinal chemistry. Benzimidizole nucleus has been found to possess various biological activities such as anticancer, antimicrobial, anti-inflammatory, antiviral, antitubercular and antidiabetic. A number of benzimidazoles such as bendamustine, pantoprazole have been approved for the treatment of various illnesses whereas galeterone and GSK461364 are in clinical trials. The present review article gives an overview about the different biological activities exhibited by the benzimidazole derivatives as well as different methods used for the synthesis of benzimidazole derivatives for the past ten years.

Pipeline of anti-Mycobacterium abscessus small molecules: Repurposable drugs and promising novel chemical entities

The Mycobacterium abscessus complex is a group of emerging pathogens that are difficult to treat. There are no effective drugs for successful M. abscessus pulmonary infection therapy, and existing drug regimens recommended by the British or the American Thoracic Societies are associated with poor clinical outcomes. Therefore, novel antibacterial drugs are urgently needed to contain this global threat. The current anti-M. abscessus small-molecule drug development process can be enhanced by two parallel strategies-discovery of compounds from new chemical classes and commercial drug repurposing. This review focuses on recent advances in the finding of novel small-molecule agents, and more particularly focuses on the activity, mode of action and structure-activity relationship of promising inhibitors from five different chemical classes-benzimidazoles, indole-2-carboxamides, benzothiazoles, 4-piperidinoles, and oxazolidionones. We further discuss some other interesting small molecules, such as thiacetazone derivatives and benzoboroxoles, that are in the early stages of drug development, and summarize current knowledge about the efficacy of repurposable drugs, such as rifabutin, tedizolid, bedaquiline, and others. We finally review targets of therapeutic interest in M. abscessus that may be worthy of future drug and adjunct therapeutic development.

Preparation of 1,2-substituted benzimidazoles via a copper-catalyzed three component coupling reaction

1,2-Substituted benzimidazoles were prepared by simply stirring a mixture of copper catalysts, N-substituted o-phenylenediamines, sulfonyl azides and terminal alkynes. Particularly, the intermediate N-sulfonylketenimine occurred with two nucleophilic addition and the sulfonyl group was eliminated via cyclization. In a way, sulfonyl azides and copper catalysts activated the terminal alkynes to synthesize benzimidazoles.

H2 Activation with Co Nanoparticles Encapsulated in N-Doped Carbon Nanotubes for Green Synthesis of Benzimidazoles

Co nanoparticles (NPs) encapsulated in N-doped carbon nanotubes (Co@NC₉₀₀ ) are systematically investigated as a potential alternative to precious Pt-group catalysts for hydrogenative heterocyclization reactions. Co@NC₉₀₀ can efficiently catalyze hydrogenative coupling of 2-nitroaniline to benzaldehyde for synthesis of 2-phenyl-1H-benzo[d]imidazole with >99 % yield at ambient temperature in one step. The robust Co@NC₉₀₀ catalyst can be easily recovered by an external magnetic field after the reaction and readily recycled for at least six times without any evident decrease in activity. Kinetic experiments indicate that Co@NC₉₀₀ -promoted hydrogenation is the rate-determining step with a total apparent activation energy of 41±1 kJ mol^-1 . Theoretical investigations further reveal that Co@NC₉₀₀ can activate both H₂ and the nitro group of 2-nitroaniline. The observed energy barrier for H₂ dissociation is only 2.70 eV in the rate-determining step, owing to the presence of confined Co NPs in Co@NC₉₀₀ . Potential industrial application of the earth-abundant and non-noble transition metal catalysts is also explored for green and efficient synthesis of heterocyclic compounds.

Synthesis and evaluation of new quinazoline-benzimidazole hybrids as potent anti-microbial agents against multidrug resistant Staphylococcus aureus and Mycobacterium tuberculosis

Owing to the rapid rise in antibiotic resistance, infectious diseases have become serious threat to public health. There is an urgent need to develop new antimicrobial agents with diverse chemical structures and novel mechanisms of action to overcome the resistance. In recent years, Quinazoline-benzimidazole hybrids have emerged as a new class of antimicrobial agents active against S. aureus and M. tuberculosis. In the current study, we designed and synthesized fifteen new Quinazoline-benzimidazole hybrids and evaluated them for their antimicrobial activity against S. aureus ATCC 29213 and M. tuberculosis H37Rv. These studies led to the identification of nine potent antibacterial agents 8a, 8b, 8c, 8d, 8f, 8g, 8h, 8i and 10c with MICs in the range of 4-64 μg/mL. Further, these selected compounds were found to possess potent antibacterial potential against a panel of drug-resistant clinical isolates which include methicillin and vancomycin-resistant S. aureus. The selected compounds were found to be less toxic to Vero cells (CC₅₀ = 40-≥200 μg/mL) and demonstrated a favourable selectivity index. Based on the encouraging results obtained these new benzimidazol-2-yl quinazoline derivatives have emerged as promising antimicrobial agents for the treatment of MDR- S. aureus and Mycobacterial infections.