Therapeutic evolution of benzimidazole derivatives in the last quinquennial period

Design, synthesis, and biological evaluation of novel benzimidazole derivatives as sphingosine kinase 1 inhibitor

Sphingosine kinase 1 (SphK1) has emerged as an attractive drug target for different diseases. Recently, discovered SphK1 inhibitors have been recommended in cancer therapeutics; however, selectivity and potency are great challenges. In this study, a novel series of benzimidazoles was synthesized and evaluated as SphK1 inhibitors. Our design strategy is twofold: It aimed first to study the effect of replacing the 5-position of the benzimidazole ring with a polar carboxylic acid group on the SphK1-inhibitory activity and cytotoxicity. Our second aim was to optimize the structures of the benzimidazoles through the elongation of the chain. The enzyme inhibition potentials against all the synthesized compounds toward SphK1 were evaluated, and the results revealed that most of the studied compounds inhibited SphK1 effectively. The binding affinity of the benzimidazole derivatives toward SphK1 was measured by fluorescence binding and molecular docking. Compounds 33, 37, 39, 41, 42, 43, and 45 showed an appreciable binding affinity. Therefore, the SphK1-inhibitory potentials of compounds 33, 37, 39, 41, 42, 43, and 45 were studied and IC₅₀ values were determined, to reveal high potency. The study showed that these compounds inhibited SphK1 with effective IC₅₀ values. Among the studied compounds, compound 41 was the most effective one with the lowest IC₅₀ value and a high cytotoxicity on a wide spectrum of cell lines. Molecular docking revealed that most of these compounds fit well into the ATP-binding site of SphK1 and form hydrogen bond interactions with catalytically important residues. Overall, the findings suggest the therapeutic potential of benzimidazoles in the clinical management of SphK1-associated diseases.

Novel pyrimidine-benzimidazole hybrids with antibacterial and antifungal properties and potential inhibition of SARS-CoV-2 main protease and spike glycoprotein

Objective

The study aimed to synthesize and characterize pyrimidine-linked benzimidazole hybrids, define their antimicrobial and antifungal activities in vitro, and determine their ability to inhibit the main protease and spike glycoprotein of SARS-CoV-2.

Methods

The ability of the synthesized compounds to inhibit the main protease and spike glycoprotein inhibitory of SARS-CoV-2 was investigated by assessing their mode of binding to the allosteric site of the enzyme using molecular docking. The structures of pyrimidine-linked benzimidazole derivatives synthesized with microwave assistance were confirmed by spectral analysis. Antibacterial and antifungal activities were determined by broth dilution.

Results

Gram-negative bateria (Escherichia coli and Pseudomonas aeruginosa) were more sensitive than gram-positive bateria (Staphylococcus aureus and Streptococcus pyogenes) to the derivatives. Candida albicans was sensitive to the derivatives at a minimal inhibitory concentration (MIC) of 250 μg/mL. The novel derivatives had better binding affinity (kcal/mol) than nelfinavir, lopinavir, ivermectin, remdesivir, and favipiravir, which are under investigation as treatment for SARS-CoV-2 infection. Compounds 2c, 2e, and 2g formed four hydrogen bonds with the active cavity of the main protease. Many derivatives had good binding affinity for the RBD of the of SARS-CoV-2 spike glycoprotein with the formation of up to four hydrogen bonds.

Conclusion

We synthesized novel pyrimidine-linked benzi-midazole derivatives that were potent antimicrobial agents with ability to inhibit the SARS-CoV-2 spike glycoprotein. Understanding the pharmacophore features of the main protease and spike glycoprotein offers much scope for the development of more potent agents. We plan to optimize the properties of the derivatives using models in vivo and in vitro so that they will serve as more effective therapeutic options against bacterial and SARS-CoV-2 infections.

Synthesis, Characterization, and Preliminary In Vitro Cytotoxic Evaluation of a Series of 2-Substituted Benzo [d] [1,3] Azoles

A series of benzo [d] [1,3] azoles 2-substituted with benzyl- and allyl-sulfanyl groups were synthesized, and their cytotoxic activities were in vitro evaluated against a panel of six human cancer cell lines. The results showed that compounds BTA-1 and BMZ-2 have the best inhibitory effects, compound BMZ-2 being comparable in some cases with the reference drug tamoxifen and exhibiting a low cytotoxic effect against healthy cells. In silico molecular coupling studies at the tamoxifen binding site of ERα and GPER receptors revealed affinity and the possible mode of interaction of both compounds BTA-1 and BMZ-2.

DARK Classics in Chemical Neuroscience: Etonitazene and Related Benzimidazoles

Etonitazene and related 2-benzylbenzimidazoles are potent analgetics invented in the research laboratories of the Swiss pharmaceutical giant CIBA in the late 1950s. Though the unprecedented structure distinguishes this class of compounds from poppy-derived and other synthetic analgetics, a range of studies indicate that these drugs are selective μ opioid receptor agonists possessing morphine-like pharmacotoxicological properties in animals as well as humans. Several unscheduled members of this synthetically readily accessible class of opioids that are not controlled under the international and national drug control systems have recently emerged on the illicit drug market. Among them, isotonitazene has been implicated in at least 200 fatalities in Europe and North America. None of the 2-benzylbenzimidazole derivatives have been developed into medicines, but etonitazene and some of its derivatives have been used as receptor probes and in addiction behavior studies in animals. The unique structure has inspired research on such benzimidazoles and related benzimidazolones of which "brorphine" made its debut as one of the newest psychoactive substance to emerge on the illicit opioid drug market in mid-2019. This in-depth review provides a historical introduction, an overview on the chemistry, pharmacological profiles, adverse effects, addiction liability, regulatory status, and the impact on chemical neuroscience of the 2-benzylbenzimidazoles. Structurally related benzimidazoles with opioid and/or analgesic properties are also discussed briefly.

Coordination compounds with heterocyclic ester derivatives. Structural characterization and anti-proliferative activity

A series of new coordination compounds of cobalt(II), copper(II) and zinc(II) with heterocyclic ester derivatives (ethyl 4-methyl-5-imidazole-carboxylate (emizco), 1-(2-(phenylsulphonyl)ethyl)-4-imidazole carboxylate (semizco)) and methyl 5-(propylthio)-2-benzimidazolecarbamate (albendazole, abz) were synthesized. They were fully characterized by different techniques such as IR, UV-Vis-NIR, elemental analysis, molar conductivity and magnetic susceptibility. Additionally, X-ray crystal structures of semizco and its [Co(semizco)₂Cl₂]·2CH₃CN 10, [Co(smmizco)₂Br₂]·2CH₃CN 11 and [Cu(semizco)₂Br₂] 15 coordination compounds are analyzed. These compounds present lone pair SO⋯π interactions between the sulfone and the imidazolic ring. These ligands showed three coordination modes: monodentate, through an imidazolic nitrogen atom, or a bidentate chelating mode by a nitrogen and an oxygen atom from the ester group. The different coordination modes and the number of coordinated ligands gave rise to tetrahedral and octahedral compounds, or for [Cu(semizco)(μ-Br)Br]_n·0.5H₂O 7 a square base pyramidal geometry. A cytotoxic study was carried out with the free ligands and their copper(II) and zinc(II) halide coordination compounds on HeLa (cervix-uterine), MCF-7 (breast), HCT-15 (colon), PC3 (prostate) human carcinoma cell lines and L929 mouse fibroblast (healthy cells). A TUNEL assay (terminal deoxynucleotidyl transferase dUTP nick end labeling) was performed with the most active copper(II) compounds to determine if cell death was by apoptosis.

Synthesis, Molecular Docking, and Biological Evaluation of Benzimidazole Derivatives as Selective Butyrylcholinesterase Inhibitors

BACKGROUND

Benzimidazole is an interesting pharmacophore which has been extensively studied in medicinal chemistry due to its high affinity towards various enzymes and receptors. Its derivatives have been previously shown to possess a wide range of biological activities including anthelmintic, antihypertensive, antiulcer, as well as anticholinesterase activity.

OBJECTIVE

The objective of this study is to search for more potent benzimidazole-based cholinesterase inhibitors, through the modification of the 1- and 2-positions of the benzimidazole core.

METHODS

Synthesis of compounds were carried out via a 4-step reaction scheme following a previously reported protocol. Structure-activity relationship of the compounds are established through in vitro cholinesterase assays and in silico docking studies. Furthermore, cytotoxicity and blood brain barrier (BBB) permeability of the compounds were also investigated.

RESULTS

Among the synthesised compounds, three of them (5IIa, 5IIb, and 5IIc) exhibited potent selective butyrylcholinesterase inhibition at low micromolar level. The compounds did not show any significant cytotoxicity when tested against a panel of human cell lines. Moreover, the most active compound, 5IIc, was highly permeable across the blood brain barrier.

CONCLUSION

In total 10 benzimidazole derivatives were synthesized and screened for their AChE and BuChE inhibitory activities. Lead compound 5Iic, represents a valuable compound for further development as potential AD therapeutics.

Benzimidazole Derivative Ameliorates Opioid-Mediated Tolerance during Anticancer- Induced Neuropathic Pain in Mice

BACKGROUND

Cancer is known to be the second significant cause of death worldwide. Chemotherapeutic agents such as platinum-based compounds are frequently used single-handedly or accompanied by additional chemotherapies to treat cancer patients. Chemotherapy-induced peripheral painful neuropathy is seen in around 40% of patients who are treated with platinum-based compounds, including cisplatin. This not only decreases the quality of life of patients but also patients' compliance with cisplatin.

OBJECTIVES

Nalbuphine, an opioid, is frequently used to treat acute and chronic pain, coupled with cisplatin in cancer patients. However, long term use of nalbuphine induces tolerance to its analgesic effects. We employed the same strategy to induce tolerance in mice.

METHODS

Here, we investigated analgesic effects of 2-[(pyrrolidin-1-yl) methyl]-1H-benzimidazole (BNZ), a benzimidazole derivative, on nalbuphine-induced tolerance during cisplatin-induced neuropathic pain using hot plate test, tail-flick tests and von Frey filament in mouse models. Furthermore, we investigated the effects of BNZ on the expression of Tumor Necrosis Factor-alpha (TNF-α) in the spinal cord.

RESULTS

The results showed that BNZ reduced tolerance to analgesic effects of nalbuphine and TNF-α expression in mice.

CONCLUSION

BNZ could be a potential drug candidate for the management of nalbuphine-induced tolerance in cisplatin-induced neuropathic pain.

Structural and biological characterization of anticancer nickel(II) bis(benzimidazole) complex

In the present study, nickel(II) complex with 2-[2-[2-(1H-benzimidazol-2-yl)ethylsulfanyl]ethyl]-1H-benzimidazole (tebb) of formula [Ni(tebb)₂](ClO₄)₂ has been prepared and its structure was proved by X-ray crystallography. The central nickel atom is in deformed octahedral vicinity. Four nitrogen atoms of two ligands form plane of octahedral and sulfur atoms are in apical positions. Perchlorate anions are outside the coordination sphere. The coordination compound was tested for its biological activities in an array of in vitro assays. It was found that the synthesized complex possesses interesting biological activity, which is most likely related to its cell-type related uptake kinetics. The synthesized complex is readily uptaken by malignant MDA-MB-231 and CACO-2 cells with the lowest uptake by healthy Hs27 fibroblasts. The lowest IC₅₀ values were obtained for MDA-MB-231 cells (5.2-12.7 μM), highlighting exceptional differential cytotoxicity (IC₅₀ values for healthy fibroblasts were 38.6-51.5 μM). Furthermore, it was found the complex is capable to cause hydrolytic DNA cleavage, promotes an efficient DNA fragmentation and to trigger an extensive formation of intracellular reactive oxygen species. Overall, current work presents a synthesis of Ni(II) coordination compound with interesting biological behavior and with a promising potential to be further tested in pre-clinical models.

Synthesis and Biological Evaluation of Benzimidazole Derivatives as Potential Neuroprotective Agents in an Ethanol-Induced Rodent Model

Alzheimer's disease (AD) is the most devastating and progressive neurodegenerative disease in middle to elder aged people, which can be exacerbated by lifestyle factors. Recent longitudinal studies demonstrated that alcohol consumption exacerbates memory impairments in adults. However, the underlying mechanism of alcohol-induced memory impairment is still elusive. The increased cellular manifestation of reactive oxygen species (ROS) and the production of numerous proinflammatory markers play a critical role in the neurodegeneration and pathogenesis of AD. Therefore, reducing neurodegeneration by decreasing oxidative stress and neuroinflammation may provide a potential therapeutic roadmap for the treatment of AD. In this study, eight new benzimidazole acetamide derivatives (FP1, FP2, FP5-FP10) were synthesized and characterized to investigate its neuroprotective effects in ethanol-induced neurodegeneration in a rat model. Further, three derivatives (FP1, FP7, and FP8) were selected for in vivo molecular analysis based on preliminary in vitro antioxidant screening assay. Molecular docking analysis was performed to assess the affinity of synthesized benzimidazole acetamide derivatives against selected proinflammatory targets (TNF-α, IL-6). Biochemical analysis revealed elevated expression of neuroinflammatory markers (TNF-α, NF-κB, IL-6, NLRP3), increased cellular oxidative stress, and reduced antioxidant enzymes in ethanol-exposed rats brain. Notably, pretreatment with new benzimidazole acetamide derivatives (FP1, FP7, and FP8) significantly modulated the ethanol-induced memory deficits, oxidative stress, and proinflammatory markers (TNF-α, NF-κB, IL-6, NLRP3) in the cortex. The multipurpose nature of acetamide containing benzimidazole nucleus and its versatile affinity toward numerous receptors highlight its multistep targeting potential. These results indicated the neuroprotective potential of benzimidazole acetamide derivatives (FP1, FP7, and FP8) as novel therapeutic candidates in ethanol-induced neurodegeneration which may partially be due to inhibition of the neuroinflammatory-oxidative stress vicious cycle.

Amino acid conjugates of 2-mercaptobenzimidazole provide better anti-inflammatory pharmacology and improved toxicity profile

Benzimidazole is an important pharmacophore for clinically active drugs against inflammation and treatment of pain, however, it is associated with gastrointestinal side effects. Here we synthesized benzimidazole based agents with significant analgesic/anti-inflammatory potential but with less gastrointestinal adverse effects. In this study, we synthesized novel, orally bioavailable 2-mercaptobenzimidazole amino acid conjugates (4a-4o) and screened them for analgesic, anti-inflammatory and gastro-protective effects. The synthesized 2-mercaptbenzimidazole derivatives were characterized for their structure using FTIR, 1 H NMR and 13 C NMR spectroscopic techniques. The 2-mercaptobenzimidazole amino acid conjugates have found to possess potent analgesic, anti-inflammatory and gastroprotective activities, particularly with compound 4j and 4k. Most of the compounds exhibited remarkable anti-ulcer and antisecretory effects. Molecular docking studies were carried out to study the binding affinities and interactions of the synthesized compounds with target proteins COX-2 (PDB ID: 3LN1) and H+ /K+ -ATPase (PDB ID: 5Y0B). Our results support the clinical promise of these newly synthesized 2-mercaptobezimidazol conjugates as a component of therapeutic strategies for inflammation and analgesia, for which the gastric side effects are always a major limitation.

Synthesis of purines and adenines containing the hexafluoroisopropyl group

Several new derivatives of adenine, purine, and theophylline containing the (CF₃)₂CH group connected to a nitrogen atom of the imidazole ring were prepared by the reaction of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1) with the corresponding substrates, resulting in the selective alkylation of one of the nitrogen atoms of the imidazole ring. The reaction proceeds under mild conditions in a polar solvent, giving the alkylated products in 47–78% yield. While for purine and 4- and 5-azabenzimidazole, the reaction led to a mixture of two isomers, the reaction of adenine and the corresponding 2-fluoro derivative was regioselective, resulting in the formation of only one isomer in each case. The alkylation of theophylline led to the formation of a new derivative of caffeine.

N-substituted benzimidazole acrylonitriles as in vitro tubulin polymerization inhibitors: Synthesis, biological activity and computational analysis

We present the design, synthesis and biological activity of novel N-substituted benzimidazole based acrylonitriles as potential tubulin polymerization inhibitors. Their synthesis was achieved using classical linear organic and microwave assisted techniques, starting from aromatic aldehydes and N-substituted-2-cyanomethylbenzimidazoles. All newly prepared compounds were tested for their antiproliferative activity in vitro on eight human cancer cell lines and one reference non-cancerous assay. N,N-dimethylamino substituted acrylonitriles 30 and 41, bearing N-isobutyl and cyano substituents placed on the benzimidazole nuclei, showed strong and selective antiproliferative activity in the submicromolar range of inhibitory concentrations (IC₅₀ 0.2-0.6 μM), while being significantly less toxic than reference systems docetaxel and staurosporine, thus promoting them as lead compounds. Mechanism of action studies demonstrated that two most active compounds inhibited tubulin polymerization. Computational analysis confirmed the suitability of the employed benzimidazole-acrylonitrile skeleton for the binding within the colchicine binding site in tubulin, thus rationalizing the observed antitumor activities, and demonstrated that E-isomers are active substances. It also provided structural determinants affecting both the binding position and the matching affinities, identifying the attached NMe₂ group as the most dominant in promoting the binding, which allows ligands to optimize favourable cation∙∙∙π and hydrogen bonding interactions with Lys352.

Cu-Catalyzed Regioselective C-H Alkylation of Benzimidazoles with Aromatic Alkenes

Herein we report a novel Cu-catalyzed regioselective C2-H alkylation of benzimidazoles with aromatic alkenes. The reaction features exclusive regioselectivity and broad substrate scope in the intermolecular alkylation of benzimidazoles with terminal and internal aromatic alkenes, constituting a modular access toward benzimidazole-containing 1,1-di(hetero)aryl alkanes. The intramolecular C2-H alkylation of benzimidazoles with aromatic alkenes has been achieved in an endo-selective manner. The enantioselective C2 alkylation of benzimidazoles has also been realized with moderate to good stereocontrol.

Alkylated benzimidazoles: Design, synthesis, docking, DFT analysis, ADMET property, molecular dynamics and activity against HIV and YFV

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New benzimidazole analogs synthesized as antivirals against HIV-1 and yellow fever virus.

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Molecular dynamics simulation studies indicated a stable ligand-protein complex of compound 3a within NNIBP of HIV-RT.

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DFT analysis confirmed the stability of hydrogen bonding interaction between the TRP 229 residue of HIV-RT and compound 3a.

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Molecules were tested for their anti-HIV and broad spectrum antiviral properties against different DNA and RNA viruses.

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Antiviral properties and cytotoxicity determined using MTT assay.

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Compound 3a showed anti-HIV activity and compound 2b showed excellent inhibition property against yellow fever virus.

A series of alkylated benzimidazole derivatives was synthesized and screened for their anti-HIV, anti-YFV, and broad-spectrum antiviral properties. The physicochemical parameters and drug-like properties of the compounds were assessed first, and then docking studies and MD simulations on HIV-RT allosteric sites were conducted to find the possible mode of their action. DFT analysis was also performed to confirm the nature of the hydrogen bonding interaction of active compounds. The in silico studies indicated that the molecules behaved like possible NNRTIs. The nature – polar or non-polar and position of the substituent present at fifth, sixth, and N-1 positions of the benzimidazole moiety played an important role in determining the antiviral properties of the compounds. Among the various compounds, 2-(5,6-dibromo-2-chloro-1H-benzimidazol-1-yl)ethan-1-ol (3a) showed anti-HIV activity with an appreciably low IC₅₀ value as 0.386 × 10⁻⁵μM. Similarly, compound 2b, 3-(2-chloro-5-nitro-1H-benzimidazol-1-yl) propan-1-ol, showed excellent inhibitory property against the yellow fever virus (YFV) with EC₅₀ value as 0.7824 × 10⁻²μM.

A new series of benzoxazole-based SIRT1 modulators for targeted therapy of non-small-cell lung cancer

In an attempt to identify potential anticancer agents for non-small-cell lung cancer (NSCLC) targeting sirtuin 1 (SIRT1), the synthesis of a new series of benzoxazoles (3a - i) was carried out through a facile and versatile synthetic route. The compounds were evaluated for their cytotoxic effects on A549 human lung adenocarcinoma and NIH/3T3 mouse embryonic fibroblast cells using the MTT assay. 2-[(5-Nitro-1H-benzimidazol-2-yl)thio]-N-(2-methylbenzoxazol-5-yl)acetamide (3e) and 2-[(5-chloro-1H-benzimidazol-2-yl)thio]-N-(2-methylbenzoxazol-5-yl)acetamide (3g) were the most potent and selective anticancer agents in this series against the A549 cell line, with IC₅₀ values of 46.66 ± 11.54 and 55.00 ± 5.00 µM, respectively. The flow cytometry-based apoptosis detection assay was performed to determine their effects on apoptosis in A549 cells. Both compounds induced apoptosis in a dose-dependent manner. The effects of compounds 3e and 3g on SIRT1 activity were determined. On the basis of in vitro studies, it was observed that compound 3g caused a significant decrease in SIRT1 levels in a dose-dependent manner, whereas compound 3e increased the SIRT1 levels. According to molecular docking studies, the substantial alteration in the type of action could be attributed to the difference between the interactions of compounds 3e and 3g with the same residues in the active site of SIRT1 (PDB code: 4IG9). On the basis of in silico ADME (absorption, distribution, metabolism, and excretion) studies, these compounds are predicted to possess favorable ADME profiles. According to the in vitro and in silico studies, compounds 3e and 3g, small-molecule SIRT1 modulators, were identified as potential orally bioavailable anticancer agents for the targeted therapy of NSCLC.

The role of imidazole and benzimidazole heterocycles in Chagas disease: A review

The haemoflagellate protozoan Trypanosoma cruzi (T. cruzi) is the causative agent of Chagas disease (CD), a potentially life-threatening disease. Little by little, remarkable progress has been achieved against CD, although it is still not enough. In the absence of effective chemotherapy, many research groups, organizations and pharmaceutical companies have focused their efforts on the search for compounds that could become viable drugs against CD. Within the wide variety of reported derivatives, this review summarizes and provides a global vision of the situation of those compounds that include broadly studied heterocycles in their structures due to their applications in medicinal chemistry: imidazole and benzimidazole rings. Therefore, the intention of this work is to present a compilation, as much as possible, of all the reported information, regarding these imidazole and benzimidazole derivatives against T. cruzi, as a starting point for future researchers in this field.

Versatile mechanisms of 2-substituted benzimidazoles in targeted cancer therapy

Background

The aim of this review is to provide an overview on diverse anticancer activities of 2-substituted benzimidazole derivatives.

Main body

This review provides a correlation between the various mechanisms of action of benzimidazoles as anticancer and the substitution pattern around the nucleus.

Conclusion

The linker group and substitution at N-1, C-2, C-5, and C-6 positions have been found to be the most contributory factors for anticancer activity. This will help in the further design to afford more selective, potent, and multi-target anticancer of 2-substituted benzimidazole-based compounds.

Application of the Sea Urchin Embryo Test in Toxicity Evaluation and Effect-Directed Analysis of Wastewater Treatment Plant Effluents

Sea urchin embryo assay was used to assess general toxicity at four wastewater treatment plant effluents of Biscay (Gorliz, Mungia, Gernika, and Galindo), and within the tested range, all the extracts showed embryo growth inhibition and skeleton malformation activities with EC₅₀ values, in relative enrichment factor units, between 1.1-16.8 and 1.1-8.8, respectively. To identify the causative compounds, effect-directed analysis was successfully applied for the first time using a sea urchin embryo test to the secondary treatment of the Galindo effluent. To this end, two subsequent fractionation steps were performed using C18 (21 fractions) and aminopropyl columns (15 fractions). By this fractionation, the number of features detected by LC-HRMS in the raw sample was drastically reduced from 1500 to 9, and among them, two pesticides (mexacarbate, 17 ng/L, and fenpropidin, 23 ng/L), two antidepressants (amitriptyline, 304 ng/L, and paroxetine, 26 ng/L), and two anthelmintic agents (mebendazole, 65 ng/L, and albendazole, 48 ng/L) could be identified in the two toxic fractions. The artificial mixture of the identified six compounds could explain 79% of the observed effect, with albendazole and paroxetine as the predominant contributors (49% and 49%, respectively) affecting the sea urchin embryogenesis activity.

Design, Synthesis and Anti-Tumor Activity of Novel Benzimidazole-Chalcone Hybrids as Non-Intercalative Topoisomerase II Catalytic Inhibitors

Chemical diversification of type II topoisomerase (Topo II) inhibitors remains indispensable to extend their anti-tumor therapeutic values which are limited by their side effects. Herein, we designed and synthesized a novel series of benzimidazole-chalcone hybrids (BCHs). These BCHs showed good inhibitory effect in the Topo II mediated DNA relaxation assay and anti-proliferative effect in 4 tumor cell lines. 4d and 4n were the most potent, with IC₅₀ values less than 5 μM, superior to etoposide. Mechanistic studies indicated that the BCHs functioned as non-intercalative Topo II catalytic inhibitors. Moreover, 4d and 4n demonstrated versatile properties against tumors, including inhibition on the colony formation and cell migration, and promotion of apoptosis of A549 cells. The structure-activity relationship and molecular docking analysis suggested possible contribution of the chalcone motif to the Topo II inhibitory and anti-proliferative potency. These results indicated that 4d and 4n could be promising lead compounds for further anti-tumor drug research.

Synthesis and Biological Evaluation of Novel (thio)semicarbazone-Based Benzimidazoles as Antiviral Agents against Human Respiratory Viruses

Respiratory RNA viruses are responsible for recurrent acute respiratory illnesses that still represent a major medical need. Previously we developed a large variety of benzimidazole derivatives able to inhibit these viruses. Herein, two series of (thio)semicarbazone- and hydrazone-based benzimidazoles have been explored, by derivatizing 5-acetyl benzimidazoles previously reported by us, thereby evaluating the influence of the modification on the antiviral activity. Compounds 6, 8, 16 and 17, bearing the 5-(thio)semicarbazone and 5-hydrazone functionalities in combination with the 2-benzyl ring on the benzimidazole core structure, acted as dual inhibitors of influenza A virus and human coronavirus. For respiratory syncytial virus (RSV), activity is limited to the 5-thiosemicarbazone (25) and 5-hydrazone (22) compounds carrying the 2-[(benzotriazol-1/2-yl)methyl]benzimidazole scaffold. These molecules proved to be the most effective antiviral agents, able to reach the potency profile of the licensed drug ribavirin. The molecular docking analysis explained the SAR of these compounds around their binding mode to the target RSV F protein, revealing the key contacts for further assessment. The herein-investigated benzimidazole-based derivatives may represent valuable hit compounds, deserving subsequent structural improvements towards more efficient antiviral agents for the treatment of pathologies caused by these human respiratory viruses.

Understanding the interaction between α-1-acid glycoprotein (AGP) and potential Cu/Zn metallo-drugs of benzimidazole derived organic motifs: A multi-spectroscopic and molecular docking study

Drug-binding and interactions with plasma proteins strongly affect their efficiency of delivery, hence considered as a key factor in determining the overall pharmacological action. Alpha-1-acid glycoprotein (AGP), a second most abundant plasma protein in blood circulation, has unique drug binding ability and involved in the transportation of various compounds. Here, we have investigated the mechanism of interaction between AGP and potential Cu/Zn metallo-drugs of benzimidazole derived organic motifs (CuL₂ and ZnL₂, where L is Schiff base ligand) by applying integrated spectroscopic, biophysical techniques and computational molecular docking analyses. We found that both the metallo-drugs (CuL₂ and ZnL₂) were bound at the central cavity of AGP interacting with the residues of lobe I, lobe II as well as lobe III. The binding of metallo-drugs to AGP occurs in 1:1 M ratios. Hydrogen bonding, electrostatic and hydrophobic interactions played a significant role in stabilizing the AGP-metallo-drug complexes. Binding affinities of both the metallo-drugs towards AGP at 298 K were of the order of 10⁴-10⁵ M^-1, corresponding to Gibbs free energy of stabilization of approximately -5.50 to -6.62 kcal mol^-1. Furthermore, the spectroscopic investigation by circular dichroism and synchronous fluorescence analyses suggest conformational changes in AGP upon the binding of metallic compounds.

Construction of All-Carbon Quaternary Stereocenters by Scandium-Catalyzed Intramolecular C-H Alkylation of Imidazoles with 1,1-Disubstituted Alkenes

The exo-selective C-H cycloaddition of imidazoles to 1,1-disubstituted alkenes has been achieved for the first time by using half-sandwich scandium catalysts. A wide range of imidazole compounds bearing various 1,1-disubstituted aliphatic alkenes, styrenes, dienes, and enynes have been selectively converted in high yields to the corresponding bicyclic imidazole derivatives bearing β-all-carbon-substituted quaternary stereocenters. By using a chiral half-sandwich scandium catalyst, the asymmetric exo-selective cyclization has also been achieved with a high level of enantioselectivity.

Bis-(imidazole/benzimidazole)-pyridine derivatives: synthesis, structure and antimycobacterial activity

Aim:

Over the last decades, few significant achievements have been made in tuberculosis (TB) therapy. As a result, there is an urgent need for new anti-TB drugs.

Results:

Two new classes of bis-(imidazole/benzimidazole)-pyridine derivatives were designed, synthesized and evaluated for their antimycobacterial activity.

Conclusion:

The synthesis is efficient and straightforward, involving only two successive N-alkylations. The anti-TB assay reveal that our compounds have an excellent anti-TB activity against both replicating and nonreplicating Mtb, are not cytotoxic, exhibited a very good intracellular activity and are active against drug-resistant Mtb strains, some compounds have a bactericidal mechanism. The absorption, distribution, metabolism, excretion and toxicity studies performed for one compound are promising, indicating that it is a good candidate for a future drug.

Benzimidazole Containing Acetamide Derivatives Attenuate Neuroinflammation and Oxidative Stress in Ethanol-Induced Neurodegeneration

Oxidative stress-induced neuroinflammation is the prominent feature of neurodegenerative disorders, and is characterized by a gradual decline of structure and function of neurons. Many biochemical events emerge thanks to the result of this neurodegeneration, and ultimately provoke neuroinflammation, activation of microglia, and oxidative stress, leading to neuronal death. This cascade not only explains the complexity of events taking place across different stages, but also depicts the need for more effective therapeutic agents. The present study was designed to investigate the neuroprotective effects of newly synthesized benzimidazole containing acetamide derivatives, 3a (2-(4-methoxyanilino)-N-[1-(4-methylbenzene-1-sulfonyl)-1H-benzimidazol-2-yl] acetamide) and 3b (2-(Dodecylamino)-N-[1-(4-methylbenzene-1-sulfonyl)-1H-benzimidazol-2-yl] acetamide) against ethanol-induced neurodegeneration in the rat model. Both derivatives were characterized spectroscopically by proton NMR (¹H-NMR) and carbon-13 NMR (¹³C-NMR) and evaluated for neuroprotective potential using different pharmacological approaches. In vivo experiments demonstrated that ethanol triggered neurodegeneration characterized by impaired antioxidant enzymes and elevated oxidative stress. Furthermore, ethanol administration induced neuroinflammation, as demonstrated by elevated expression of tumor necrotic factor (TNF-α), nuclear factor κB (NF-κB), cyclooxygenase-2 (COX2), and ionized calcium-binding adapter molecule-1 (Iba-1), which was further validated by enzyme-linked immunosorbent assay (ELISA). Treatment with 3a and 3b ameliorated the ethanol-induced oxidative stress, neuroinflammation, and memory impairment. The affinity of synthesized derivatives towards various receptors involved in neurodegeneration was assessed through docking analysis. The versatile nature of benzimidazole nucleus and its affinity toward several receptors suggested that it could be a multistep targeting neuroprotectant. As repetitive clinical trials of neuroprotectants targeting a single step of the pathological process have failed previously, our results suggested that a neuroprotective strategy of acting at different stages may be more advantageous to intervene in the vicious cycles of neuroinflammation.

Synthesis of benzo[4,5]imidazo[1,2-a]quinoxalines by I2-mediated sp3 C–H amination

Benzo[4,5]imidazo[1,2-a]quinoxalines were synthesized by I₂-mediated sp³ C–H amination under transition-metal free conditions in an efficient and scalable fashion.

Recent advances in the use of benzimidazoles as corrosion inhibitors

Background

Benzimidazole, a key heterocycle in therapeutic chemistry, and its derivatives, are recently mentioned in the literature as corrosion inhibitors for steels (CS, MS), pure metals (Fe, Al, Cu, Zn) and alloys. Benzimidazoles are good corrosion inhibitors for extremely aggressive, corrosive acidic media such as 1 M HCl, 1 M HNO₃, 1.5 M H₂SO₄, basic media, 0.1 M NaOH or salt solutions. Benzimidazole derivatives act as mixed type inhibitors, exhibiting stronger inhibitive effect on the cathodic reaction than on the anodic one.

Conclusion

These review highlights recent research in the field of benzimidazole compounds that their role as corrosion inhibitors, the structure of the compounds, electrochemical studies, the experimental conditions, the proposed mechanisms as well as the quantum theoretical studies that predict the structure of the compounds with inhibition properties.

Synthesis and Biological Evaluation of Structurally Diverse Benzimidazole Scaffolds as Potential Chemotherapeutic Agents

BACKGROUND AND OBJECTIVE

Drug resistance and adverse effects are immense healthcare challenges in cancer therapy. Benzimidazole ring-based small molecules have been effective anticancer agents in drug development. In an effort to develop novel chemotherapeutics, we synthesized and assessed the anticancer and antibacterial activities of a small library of structurally unique benzimidazoles.

METHODS

The benzimidazoles were derived from indole, N-alkyl indole, fatty acid, and alpha-amino acid scaffolds providing a panel of diverse structures. The compounds were tested in three different cancer cell lines for cytotoxicity: HepG2 (human hepatocellular carcinoma), HeLa (human cervical carcinoma), and A549 (human lung carcinoma). Mechanism of cell death induced by benzimidazoles was evaluated using fluorescent dye-based apoptosis-necrosis assay, immunoblotting for active caspases, topoisomerase-II activity assay, and cell cycle assay.

RESULTS

Cell viability testing revealed that indole- and fatty acid-based benzimidazoles were most potent followed by the amino acid derivatives. Many compounds induced cytotoxicity in a concentration-dependent manner with cellular cytotoxicity (CC50) <20μM in the cell lines tested. Most compounds exhibited cytotoxicity via apoptosis through the intrinsic pathway. Inhibition of topoisomerase activity and cell cycle alterations were not the primary mechanisms of cytotoxicity. In addition, several compounds showed promising activity against S. aureus and S. epidermidis (Minimum Inhibitory Concentration (MIC) of as low as 0.04μmol/mL).

CONCLUSION

The reported benzimidazole derivatives possess promising anticancer and antibacterial properties. Additionally, we discovered apoptosis to be the primary mechanism for cancer cell death induced by the tested benzimidazoles. Our findings suggest that further development of these scaffolds could provide drug leads towards new chemotherapeutics.

Crystal structure of bis[2-(1H-benzimidazol-2-yl-κN 3)aniline-κN]bis(nitrato-κO)cadmium(II)

The synthesis and crystal structure of the title 2-(1H-benzimidazol-2-yl)aniline Cd^II complex is reported in which the Cd^II atom lies on a twofold rotation axis and is coordinated by four N atoms, provided by two bidentate 2-(1H-benzimidazol-2-yl)aniline ligands, and two nitrato O atoms, forming a distorted octa­hedral geometry.

In the title compound, [Cd(NO₃)₂(C₁₃H₁₁N₃)₂], the Cd^II atom lies on a twofold rotation axis and is coordinated by four N atoms and two O atoms, provided by two bidentate 2-(1H-benzimidazol-2-yl)aniline ligands, and two nitrato O atoms, forming a distorted octa­hedral geometry [range of bond angles around the Cd atom = 73.82 (2)–106.95 (8)°]. In the ligand, the dihedral angle between the aniline ring and the benzimidazole ring system is 30.43 (7)°. The discrete complex mol­ecule is stabilized by an intra­molecular N—H⋯O hydrogen bond. In the crystal, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules, forming a three-dimensional network.

A Comprehensive Review on the Therapeutic Versatility of Imidazo [2,1-b]thiazoles

BACKGROUND

Imidazo[2,1-b]thiazole, a well-known fused five-membered hetrocycle is one of the most promising and versatile moieties in the area of medicinal chemistry. Derivatives of imidazo[2,1-b]thiazole have been investigated for the development of new derivatives that exhibit diverse pharmacological activities. This fused heterocycle is also a part of a number of therapeutic agents.

OBJECTIVE

To review the extensive pharmacological activities of imidazo[2,1-b]thiazole derivatives and the new molecules developed between 2000-2018 and their usefulness.

METHOD

Thorough literature review of all relevant papers and patents was conducted.

CONCLUSION

The present review, covering a number of aspects, is expected to provide useful insights in the design of imidazo[2,1-b]thiazole-based compounds and would inspire the medicinal chemists for a comprehensive and target-oriented information to achieve a major breakthrough in the development of clinically viable candidates.