Design and synthesis of 2-arylbenzimidazoles and evaluation of their inhibitory effect against Chlamydia pneumoniae

Benzimidazolone-piperazine/triazole/thiadiazole/furan/thiophene conjugates: Synthesis, in vitro urease inhibition, and in silico molecular docking studies

This study describes the synthesis, in vitro urease inhibition, and molecular docking studies of benzimidazolone derivatives incorporating the piperazine, triazole, thiadiazole, furan, thiophene, and thiosemicarbazide moieties. All newly synthesized compounds demonstrated varying degrees of urease inhibitory activity, with IC50 values ranging between 0.64 ± 0.099 and 0.11 ± 0.017 µM, when compared with the standard drug thiourea (IC50 value of 0.51 ± 0.028 µM). To confirm the experimental urease inhibition results and elucidate the mode of interaction of the synthesized compounds with the binding site of the urease enzyme, molecular docking studies were performed using the Schrödinger Suite package. Molecular docking studies showed that compounds with high in vitro urease inhibition interacted with key residues of the urease active site such as His221, Glu222, Asp223, His322, Arg338, and Ni2+ cations via hydrogen bonding, metal coordination, salt bridge, π-π stacking, and π-cation interactions.

Design, Biological Evaluation, and Computer-Aided Analysis of Dihydrothiazepines as Selective Antichlamydial Agents

Chlamydia trachomatis (CT) causes the most prevalent sexually transmitted bacterial disease in the United States. The lack of drug selectivity is one of the main challenges of the current antichlamydial pharmacotherapy. The metabolic needs of CT are controlled, among others, by cylindrical proteases and their chaperones (e.g., ClpX). It has been shown that dihydrothiazepines can disrupt CT-ClpXP. Based on this precedent, we synthesized a dihydrothiazepine library and characterized its antichlamydial activity using a modified semi-high-throughput screening assay. Then, we demonstrated their ability to inhibit ClpX ATPase activity in vitro, supporting ClpX as a target. Further, our lead compound displayed a promising selectivity profile against CT, acceptable cytotoxicity, no mutagenic potential, and good in vitro stability. A two-dimensional quantitative structure-activity relationship (2D QSAR) model was generated as a support tool in the identification of more potent antichlamydial molecules. This study suggests dihydrothiazepines are a promising starting point for the development of new and selective antichlamydial drugs.

Cucurbit[6]uril-Supported Fe3O4 Magnetic Nanoparticles Catalyzed Green and Sustainable Synthesis of 2-Substituted Benzimidazoles via Acceptorless Dehydrogenative Coupling

A new composite, cucurbit[6]uril (CB[6])-supported magnetic nanoparticles, Fe₃O₄-CB[6], was synthesized via a co-precipitation method in air and fully characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, inductively coupled plasma-mass spectrometry, and vibrating sample magnetometry techniques. It has been found to be a highly efficient, economic, and sustainable heterogeneous catalyst and has been employed for the first time for the synthesis of a series of biologically important 2-substituted benzimidazoles from various benzyl alcohols and 1,2-diaminobenzenes under solvent-free conditions via acceptorless dehydrogenative coupling to afford the corresponding products in good to excellent yields (68-94%). The magnetic nature of the nanocomposite facilitates the facile recovery of the catalyst from the reaction mixture by an external magnet. The catalyst can be reused up to five times with negligible loss in its catalytic activity. All the isolated products were characterized by ¹H and ¹³C{¹H} NMR spectroscopy.

Discovery and computational studies of 2-phenyl-benzoxazole acetamide derivatives as promising P2Y14R antagonists with anti-gout potential

The P2Y₁₄ nucleotide receptor, a subtype of P2Y receptors, is implicated in many human inflammatory diseases. Based on the identification of favorable residues of two screening hits in the almost symmetrical P2Y₁₄ binding domain, we describe the structural optimization of previously identified virtual screening hits 6 and 7 that result in the development of P2Y₁₄R antagonists with a novel 2-phenyl-benzoxazole acetamide chemical scaffold. Notably, compound 52 showed potent P2Y₁₄R antagonistic activity (IC₅₀ = 2 nM), and a stronger inhibitory effect on MSU-induced inflammatory in vitro, better than a previously described P2Y₁₄R antagonist PPTN. In vivo evaluation demonstrated that compound 52 also had satisfactory inhibitory activity on the inflammatory response of gout flares in mice. Moreover, P2Y₁₄R antagonist 52 decreased paw swelling and inflammatory cell infiltration through cAMP/NLRP3/GSDMD signaling pathways in MSU-induced acute gouty arthritis mice. The discussions on the binding mechanism that employ MM/GBSA free energy calculations/decompositions also provide some useful clues for further structural designing of compound 52. Taken together, 2-phenyl-benzoxazole acetamide derivative 52 with potent P2Y₁₄R antagonistic activity and in vivo potency could be a promising strategy for gout therapy and deserves further optimization.

Discovery of new 2-phenyl-1H-benzo[d]imidazole core-based potent α-glucosidase inhibitors: Synthesis, kinetic study, molecular docking, and in vivo anti-hyperglycemic evaluation

In the present study, a series of 2-phenyl-1H-benzo[d]imidazole-based α-glucosidase inhibitors were synthesized and evaluated for their in vitro and in vivo anti-diabetic potential. Screening of an in-house library revealed a moderated α-glucosidase inhibitor, 6a with 3-(1H-benzo[d]imidazol-2-yl)aniline core, and then the structural optimization was performed to obtain more efficient derivatives. Most of these derivatives showed increased activity than 6a, and the most promising inhibitors were found to be compounds 15o and 22d with IC₅₀ values of 2.09 ± 0.04 and 0.71 ± 0.02 µM, respectively. Fluorescence quenching experiment confirmed the direct binding of compounds 15o and 22d with α-glucosidase. Kinetic study revealed that both compounds were non-competitive inhibitors, that was consistent with the result of molecular docking studies where they located at the allosteric site of the enzyme. Cell viability evaluation demonstrated the non-cytotoxicity of 15o and 22d against LO2 cells. Furthermore, the in vivo pharmacodynamic study revealed that compound 15o showed significant hypoglycemic activity and improved oral sucrose tolerance, comparable to the positive control acarbose.

In-silico driven design and development of spirobenzimidazo-quinazolines as potential DNA gyrase inhibitors

DNA gyrase and Topoisomerase IV are promising antibacterial drug targets as they regulate bacterial DNA replication and topology. In a quest for novel DNA topoisomerase inhibitors, a multidisciplinary approach was adopted that involves computational prediction of binding sites and molecular modelling followed by green synthesis and biological evaluation of antibacterial activity of spirobenzimidazo quinazolines derivatives. Using basic quantum chemistry principles, we evaluated spirobenzimidazo quinazolines derivatives with their pharmacokinetic profiles. Based on the results of the aforesaid in-silico studies, we synthesized a series of titled compounds using green synthetic methodology that were validated as potential antimicrobial agents. Quantum chemoinformatics based predicted activity for the synthesized compounds 9b, 9c, and 9j was concomitant with biological evaluation of broadspectrum antibacterial activity. Biological evaluation revealed that inhibition of biofilm formation was due to their potential antibacterial activity. We believe that the novel spirobenzimidazo quinazolines have the potential to be alternatives to aminocoumarins and classical quinazolines upon detailed target specific biological studies.

Synthesis and Antimycobacterial Activity of 2,5-Disubstituted and 1,2,5-Trisubstituted Benzimidazoles

The appearance of drug-resistant strains of Mycobacterium tuberculosis and the dramatic increase in infection rates worldwide evidences the urgency of developing new and effective compounds for treating tuberculosis. Benzimidazoles represent one possible source of new compounds given that antimycobacterial activity has already been documented for some derivatives, such as those bearing electron-withdrawing groups. The aim of this study was to synthesize two series of benzimidazoles, di- and trisubstituted derivatives, and evaluate their antimycobacterial activity. Accordingly, 5a and 5b were synthesized from hydroxymoyl halides 3a and 3b, and nitro-substituted o-phenylenediamine 4. Compound 11 was synthesized from an aromatic nitro compound, 4-chloro-1,2-phenylenediamine 9, mixed with 3-nitrobenzaldehyde 10, and bentonite clay. Although the synthesis of 11 has already been reported, its antimycobacterial activity is herein examined for the first time. 1,2,5-trisubstituted benzimidazoles 7a, 7b, and 12 were obtained from N-alkylation of 5a, 5b, and 11. All benzimidazole derivatives were characterized by FT-IR, NMR, and HR-MS, and then screened for their in vitro antimycobacterial effect against the M. tuberculosis H37Rv strain. The N-alkylated molecules (7a, 7b, and 12) generated very limited in vitro inhibition of mycobacterial growth. The benzimidazoles (5a, 5b, and 11) showed in vitro potency against mycobacteria, reflected in minimal inhibitory concentration (MIC) values in the range of 6.25-25 μg/mL. Consequently, only the 2,5-disubstituted benzimidazoles were assessed for biological activity on mouse macrophages infected with M. tuberculosis. A good effect was found for the three compounds. The cytotoxicity assay revealed very low toxicity for all the test compounds against the macrophage cell line. According to the docking study, 2,5-disubstituted benzimidazoles exhibit high affinity for an interdomain cleft that plays a key role in the GTP-dependent polymerization of the filamentous temperature-sensitive Z (FtsZ) protein. The ability of different benzimidazoles to impede FtsZ polymerization is reportedly related to their antimycobacterial activity. On the other hand, the 1,2,5-trisubstituted benzimidazoles docked to the N-terminal of the protein, close to the GTP binding domain, and did not show strong binding energies. Overall, 5a, 5b, and 11 proved to be good candidates for in vivo testing to determine their potential for treating tuberculosis.

Design, synthesis, antifungal activity and 3D-QSAR study of novel pyrazole carboxamide and niacinamide derivatives containing benzimidazole moiety

The synthesized pyrazole carboxamide and niacinamide derivatives containing a benzimidazole moiety showed effective inhibition of the fungus B. cinereal growth. The 3D-QSAR model was built and revealed fine predictive ability.

Lead Discovery Strategies for Identification of Chlamydia pneumoniae Inhibitors

Throughout its known history, the gram-negative bacterium Chlamydia pneumoniae has remained a challenging target for antibacterial chemotherapy and drug discovery. Owing to its well-known propensity for persistence and recent reports on antimicrobial resistence within closely related species, new approaches for targeting this ubiquitous human pathogen are urgently needed. In this review, we describe the strategies that have been successfully applied for the identification of nonconventional antichlamydial agents, including target-based and ligand-based virtual screening, ethnopharmacological approach and pharmacophore-based design of antimicrobial peptide-mimicking compounds. Among the antichlamydial agents identified via these strategies, most translational work has been carried out with plant phenolics. Thus, currently available data on their properties as antichlamydial agents are described, highlighting their potential mechanisms of action. In this context, the role of mitogen-activated protein kinase activation in the intracellular growth and survival of C. pneumoniae is discussed. Owing to the complex and often complementary pathways applied by C. pneumoniae in the different stages of its life cycle, multitargeted therapy approaches are expected to provide better tools for antichlamydial therapy than agents with a single molecular target.

In vivo assessment of newly synthesized achiral copper(ii) and zinc(ii) complexes of a benzimidazole derived scaffold as a potential analgesic, antipyretic and anti-inflammatory

Two new complexes of copper(ii) and zinc(ii) were synthesized and characterized using various spectroscopic techniques. The newly synthesized compounds were screened for analgesic, antipyretic and anti-inflammatory activities.

A benzimidazole derivative exhibiting antitumor activity blocks EGFR and HER2 activity and upregulates DR5 in breast cancer cells

Aberrant expression or function of epidermal growth factor receptor (EGFR) or the closely related human epidermal growth factor receptor 2 (HER2) can promote cell proliferation and survival, thereby contributing to tumorigenesis. Specific antibodies and low-molecular-weight tyrosine kinase inhibitors of both proteins are currently in clinical trials for cancer treatment. Benzimidazole derivatives possess diverse biological activities, including antitumor activity. However, the anticancer mechanism of 5a (a 2-aryl benzimidazole compound; 2-chloro-N-(2-p-tolyl-1H-benzo[d]imidazol-5-yl)acetamide, C₁₆H₁₄ClN₃O, MW299), a novel 2-aryl benzimidazole derivative, toward breast cancer is largely unknown. Here, we demonstrate that 5a potently inhibited both EGFR and HER2 activity by reducing EGFR and HER2 tyrosine phosphorylation and preventing downstream activation of PI3K/Akt and MEK/Erk pathways in vitro and in vivo. We also show that 5a inhibited the phosphorylation of FOXO and promoted FOXO translocation from the cytoplasm into the nucleus, resulting in the G1-phase cell cycle arrest and apoptosis. Moreover, 5a potently induced apoptosis via the c-Jun N-terminal kinase (JNK)-mediated death receptor 5 upregulation in breast cancer cells. The antitumor activity of 5a was consistent with additional results demonstrating that 5a significantly reduced tumor volume in nude mice in vivo. Analysis of the primary breast cancer cell lines with HER2 overexpression further confirmed that 5a significantly inhibited Akt Ser473 and Bad Ser136 phosphorylation and reduced cyclin D3 expression. On the basis of our findings, further development of this 2-aryl benzimidazole derivative, a new class of multitarget anticancer agents, is warranted and represents a novel strategy for improving breast cancer treatment.

Trichloroisocyanuric Acid/Triphenylphosphine-Mediated Synthesis of Benzimidazoles, Benzoxazoles, and Benzothiazoles

A new and efficient method for preparation of benzimidazoles, benzoxazoles, and benzothiazoles from reactions of different carboxylic acids with o-phenylenediamine, o-aminophenol, and o-aminothiophenol in the presence of triphenylphosphine/trichloroisocyanuric acid system is presented. The desired products have been characterised on the basis of spectral (infrared, NMR, mass spectrometry) data, and the mechanism of their formation is proposed. The remarkable advantages are the inexpensive and readily available reagent, simple procedure, mild conditions, and good-to-excellent yields.

Metal catalyst free one-pot synthesis of 2-arylbenzimidazoles from α-aroylketene dithioacetals

An efficient green synthetic approach has been developed towards the synthesis of 2-aryl substituted benzimidazoles 4 from α-aroylketene dithioacetals (AKDTAs) 1 and phenylenediamine (OPD) 2.

Synthesis and biological evaluation of pyrazolo[4,3-d]pyrimidine analogues

A series of pyrazolo[3,4-d]pyrimidine analogues 3, 4, 5a-f, 6a-f with various amines and ester groups at C-4 and N-1 were synthesized and evaluated for antitumour activity. They were also evaluated for xanthine oxidase inhibitory activity, with most compounds having no significant impact. Compound 5e had the strongest activity against human hepatoma carcinoma cells 7402 and 7221, with half-maximal inhibitory concentration values of 4.55 and 6.28, respectively. Structure-activity relationship studies indicate that chlorine atoms in the structure of 4-((4-(substituted amides)phenyl)amino pyrazolo[4,3-d]pyrimidine analogues is crucial for antitumour activity.

Microwave-assisted synthesis of sec/tert-butyl 2-arylbenzimidazoles and their unexpected antiproliferative activity towards ER negative breast cancer cells

A new series of N-sec/tert-butyl 2-arylbenzimidazole derivatives was synthesised in 85-96% yields within 2-3.5 min by condensing ethyl 3-amino-4-butylamino benzoate with various substituted metabisulfite adducts of benzaldehyde under focused microwave irradiation. The benzimidazole analogues were characterised using (1)H NMR, (13)C NMR, high resolution MS and melting points. Evaluation of antiproliferative activity of the benzimidazole analogues against MCF-7 and MDA-MB-231 revealed several compounds with unexpected selective inhibitions of MDA-MB-231 in micromolar range. All analogues were found inactive towards MCF-7. The most potent inhibition against MDA-MB-231 human breast cancer cell line came from the unsubstituted 2-phenylbenzimidazole 10a.

Discovery of benzimidazole derivatives as novel multi-target EGFR, VEGFR-2 and PDGFR kinase inhibitors

Multi-target EGFR, VEGFR-2 and PDGFR inhibitors are highly useful anticancer agents with improved therapeutic efficacies. In this work, we used two virtual screening methods, support vector machines (SVM) and molecular docking, to identify a novel series of benzimidazole derivatives, 2-aryl benzimidazole compounds, as multi-target EGFR, VEGFR-2 and PDGFR inhibitors. 2-Aryl benzimidazole compounds were synthesized and their biological activities against a tumor cell line HepG-2 and specific kinases were evaluated. Among these compounds, compounds 5a and 5e exhibited high cytotoxicity against HepG-2 cells with IC₅₀ values at ∼2 μM. Further kinase assay study showed that compound 5a have good EGFR inhibitory activity and moderate VEGFR-2 and PDGFR inhibitory activities, while 5e have moderate EGFR inhibitory activity and slightly weaker VEGFR-2 and PDGFR inhibitory activities. Molecular docking analysis suggested that compound 5a more tightly interacts with EGFR and PDGFR than compound 5e. Our study discovered a novel series of benzimidazole derivatives as multi-target EGFR, VEGFR-2 and PDGFR kinases inhibitors.