Synthesis, antimicrobial and antiviral activity of substituted benzimidazoles

Benzimidazole(s): synthons, bioactive lead structures, total synthesis, and the profiling of major bioactive categories

Benzimidazole, a fused bicyclic compound with benzene and pentacyclic 1,3-diazole moeities, has a simple aromatic heterocyclic structure. The moiety has become an indispensable anchor for the development of new pharmacologically active products, and has yielded several therapeutic agents with anticancer, antihypertensive, antimicrobial, antifungal and antiulcer effects. Benzimidazoles, as synthetically feasible and pharmacophoric synthons, have been relentlessly pursued for the preparation of new analogues and derivatives, and they have successfully developed into some of the most sought-after and vital pharmacophores for drug discovery. The use of varied substituents and differing patterns around the benzimidazole nucleus has provided a wide spectrum of biological activities. In addition, the benzimidazole moiety constitutes a building block for the production of several drugs, drug candidates, new chemical entities, and lead molecules. The importance of this nucleus for bioactivity, e.g., antibacterial, antitubercular, antidiabetic, anticancer, antifungal, anti-inflammatory, analgesic, antioxidant, antihistaminic, and antimalarial activity, has led us to take note and provide an overview of the synthetic development approaches for various benzimidazole derivatives together with their biological actions. This review is projected to further assist in the design and development of new benzimidazole-based compounds for new and optimized pharmacologically active products towards new drug-development strategies.

Antibacterial and antifungal pyrazoles based on different construction strategies

The growing prevalence of microbial infections, and antimicrobial resistance (AMR) stemming from the overuse and misuse of antibiotics, call for novel therapeutic agents, particularly ones targeting resistant microbial strains. Scientists are striving to develop innovative agents to tackle the rising microbial infections and abate the risk of AMR. Pyrazole, a five-membered heterocyclic compound belonging to the azole family, is a versatile scaffold and serves as a core structure in many drugs with antimicrobial and other therapeutic effects. In this review, we have updated pyrazole-based antibacterial and antifungal agents mainly developed between 2016 and 2024, by combining with diverse pharmacophores such as coumarin, thiazole, oxadiazole, isoxazole, indole, etc. Meanwhile, the various strategies (molecular hybridization, bioisosterism, scaffold hopping, multicomponent reactions, and catalyst-free synthesis) for integrating different functional groups with the pyrazole ring are discussed. Additionally, structure-activity relationships of these pyrazole derivatives, i.e., how structural modifications impact their selectivity and therapeutic potential against bacterial and fungal strains, are highlighted. This review provides insights into designing next-generation antimicrobials to combat AMR, and offers valuable perspectives to the scientists working on heterocyclic compounds with diverse bioactivities.

Benzimidazole Conjugates as Multi-target Anticancer Agents - A Comprehensive Review

Cancer is the second leading cause of mortality globally and is characterized by a multifactorial etiology. Drug resistance and multidrug resistance are the reasons for the failure of many anticancer drugs that are in clinical practice now. The current review is a complete review of benzimidazole hybrids with different heterocyclic rings, which are potential anticancer agents. We reviewed around 70 research works of benzimidazole hybrids published in high-impact journals, along with a short discussion of structural features responsible for its activity against various cancers. This review highlighted benzimidazole hybrids as targeted anticancer agents with effects on multiple targets. Researchers working on targeted medications for cancer treatment will benefit from this review when designing new scaffolds with benzimidazole moieties.

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).

Benzimidazole and piperidine containing novel 1,2,3-triazole hybrids as anti-infective agents: Design, synthesis, in silico and in vitro antimicrobial efficacy

Cu alkyne-azide cycloaddition was used to easily synthesize a library of novel heterocycles containing benzimidazole and piperidine based 1,2,3-triazole(7a-7l) derivatives. The synthesized analogs were characterized by various spectroscopic techniques like FTIR, 1 H nuclear magnetic resonance (NMR), 13 C NMR, and mass spectrometry. All these novel bioactive compounds (7a-7l) were evaluated for in vitro antibacterial and antifungal efficacy. Compound 7k exhibited appreciable potent activity against Escherichia coli strain. Compounds 7a, 7b, 7f, and 7i showed excellent potent activity against all bacterial strains. Compound 7b, 7c, 7d, and 7g derivatives showed excellent effects when tested in vitro for antifungal activity against various fungal strains. Additionally, a molecular docking investigation revealed that compound 7k has the ability to bind to the active site of the E. coli DNA gyrase subunit protein and form hydrogen bonds with significant amino acid residues Asp73 and Asp49 in the active sites. In a 100 ns molecular dynamics simulation, the E. coli DNA gyrase protein's steady capacity to bind compound 7k was shown by the low measured root mean square deviation, which was an indication of the complex's conformational stability.

Synthesis, antimicrobial activity and molecular docking study of benzyl functionalized benzimidazole silver(I) complexes

In this study, a series of N-functionalized benzimidazole silver(I) complexes were prepared and characterized by FT-IR, 1H, 13C{1H} NMR spectroscopy, and elemental analysis. Synthesized N-benzylbenzimidazole silver(I) complexes were evaluated for their antimicrobial activities against bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and the fungal strains Candida albicans and Candida glabrata. The results indicated that N-alkylbenzimidazole silver(I) complexes exhibited good antimicrobial activity compared to N-alkylbenzimidazole derivatives. Especially, complex 2e presented perfect antimicrobial activity than the other complexes. The characterized molecules were optimized by DFT-based calculation methods and the optimized molecules were analyzed in detail by molecular docking methods against bacterial DNA-gyrase and CYP51. The amino acid residues detected for both target molecules are consistent with expectations, and the calculated binding affinities and inhibition constants are promising for further studies. A series of N-alkylbenzimidazole silver(I) complexes were synthesized and fully characterized by means of 1H NMR, 13C NMR, and FT-IR spectroscopies. Synthesized N-alkylbenzimidazole silver(I) complexes were investigated for their antimicrobial activities against bacteria Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and the fungal strains Candida albicans and Candida glabrata. All complexes showed better activity according to Ampicilin against Pseudomonas aeruginosa. The molecules which were firstly optimized by DFT-based calculation methods were also analyzed by molecular docking methods against DNA gyrase of E. Coli and CYP51. 338 × 190 mm (96 × 96 DPI).

Elucidation of the anti-plasmodial activity of novel imidazole and oxazole compounds through computational and in vivo experimental approaches

The development of resistance to conventional antimalarial therapies, along with the unfavorable impact of the COVID-19 pandemic on the global malaria fight, necessitates a greater focus on the search for more effective antimalarial drugs. Targeting a specific enzyme of the malaria parasite to alter its metabolic pathways is a reliable technique for finding antimalarial drug candidates. In this study, we used an in silico technique to test four novel imidazoles and an oxazole derivative for inhibitory potential against Plasmodium lactate dehydrogenase (pLDH), a unique glycolytic enzyme necessary for parasite survival and energy production. The promising imidazole compounds and the oxazole derivative were then tested for anti-plasmodial efficacy in Plasmodium berghei-infected mice. With a binding energy of -6.593 kcal/mol, IM-3 had the best docking score against pLDH, which is close to that of NADH (-6.758 kcal/mol) and greater than that of chloroquine (-3.917 kcal/mol). The test compounds occupied the enzyme's NADH binding site, with IM-3 forming four hydrogen bonds with Thr-101, Pro-246, His-195 and Asn-140. Infected mice treatment with IM-3, IM-4 and OX-1 exhibited significantly reduced parasitemia over a four-day treatment period when compared to the infected untreated animals. At 5, 10 and 20 mg/kg, IM-3 demonstrated the highest anti-plasmodial activity, suppressing parasitemia by 86.13, 97.71 and 94.11%, respectively. PCV levels were restored by IM-3 and IM-4, and the three selected compounds reduced the lipid peroxidation induced by P. berghei infection in mice. Thus, these compounds may be considered for further development as antimalarial medicines.Communicated by Ramaswamy H. Sarma.

The medicinal panorama of benzimidazoles and their scaffolds as anticancer and antithrombotic agents: A review

Nitrogen-containing heterocyclic scaffolds have become a prospective pharmacophore with therapeutic importance due to their biological similarities with natural and synthetic drugs. Among all nitrogen heterocyclic compounds, benzimidazoles and their derivatives are privileged molecules structurally akin to naturally available nucleotides, enabling them to intercommunicate with numerous biopolymers in biological systems. This reason enlightens modern researchers worldwide to assess their potential significance in the context of synthetic and biological chemistry. Therefore, it is crucial to merge the latest data with the prior documentation to apprehend the ongoing situation of the benzimidazole moiety in various therapeutic zones of research. The current work displays that the benzimidazole center is a versatile nucleus that offers the necessary data of synthetic alterations for pre-existing compounds to provide new scaffolds to resist numerous therapeutic sectors, including those associated with anticancer and antithrombosis. Due to the potential significance of benzimidazoles, this review aims to emphasize the latest innovations in synthesizing several other notable benzimidazole substrates and their significant pharmacological prospects for the future, including anticancer and antithrombosis.

New Pyrazolo-Benzimidazole Mannich Bases with Antimicrobial and Antibiofilm Activities

A new series of pyrazolo-benzimidazole hybrid Mannich bases were synthesized, characterized by ¹H-NMR, ¹³C-NMR, IR, UV-Vis, MS, and elemental analysis. In vitro cytotoxicity of the new compounds studied on fibroblast cells showed that the newly synthesized pyrazolo-benzimidazole hybrid derivatives were noncytotoxic until the concentration of 1 μM and two compounds presented a high degree of biocompatibility. The antibacterial and antibiofilm activity of the newly synthesized compounds was assayed on Gram-positive Staphylococcus aureus ATCC25923, Enterococcus faecalis ATCC29212, and Gram-negative Pseudomonas aeruginosa ATCC27853, Escherichia coli ATCC25922 strains. All synthesized compounds 5a–g are more active against all three tested bacterial strains Staphylococcus aureus ATCC25923, Enterococcus faecalis ATCC29212, and Escherichia coli ATCC25922 than reference drugs (Metronidazole, Nitrofurantoin), with the exception of compounds 5d and 5g, which are less active compared to Nitrofurantoin, and all synthesized compounds 5a–g are more active against Pseudomonas aeruginosa ATCC27853 compared to reference drugs (Metronidazole, Nitrofurantoin). Compound 5f showed the best activity against Staphylococcus aureus ATCC 25923, with a MIC of 150 μg/mL and has also inhibited the biofilm formed by all the bacterial strains, having an MBIC of 310 µg/mL compared to the reference drugs (Metronidazole, Nitrofurantoin).

Reusable Nano-Zirconia-Catalyzed Synthesis of Benzimidazoles and Their Antibacterial and Antifungal Activities

In this article, a zirconia-based nano-catalyst (Nano-ZrO2), with intermolecular C-N bond formation for the synthesis of various benzimidazole-fused heterocycles in a concise method is reported. The robustness of this reaction is demonstrated by the synthesis of a series of benzimidazole drugs in a one-pot method. All synthesized materials were characterized using 1HNMR, 13CNMR, and LC-MS spectroscopy as well as microanalysis data. Furthermore, the synthesis of nano-ZrO2 was processed using a standard hydrothermal technique in pure form. The crystal structure of nano-ZrO2 and phase purity were studied, and the crystallite size was calculated from XRD analysis using the Debye-Scherrer equation. Furthermore, the antimicrobial activity of the synthesized benzimidazole drugs was evaluated in terms of Gram-positive, Gram-negative, and antifungal activity, and the results were satisfactory.

Synthesis of biologically active heterocyclic compounds from allenic and acetylenic nitriles and related compounds

Cyclic and polycyclic compounds containing moieties such as imidazole, pyrazole, isoxazole, thiazoline, oxazine, indole, benzothiazole and benzoxazole benzimidazole are prized molecules because of the various pharmaceutical properties that they display. This led Prof. Landor and co-workers to engage in the synthesis of several of them such as alkylimidazolenes, oxazolines, thiazolines, pyrimidopyrimidines, pyridylpyrazoles, benzoxazines, quinolines, pyrimidobenzimidazoles and pyrimidobenzothiazolones. This review covers the synthesis of biologically active heterocyclic compounds by the Michael addition and the double Michael addition of various amines and diamines on allenic nitriles, acetylenic nitriles, hydroxyacetylenic nitriles, acetylenic acids and acetylenic aldehydes. The heterocycles were obtained in one step reaction and in most cases, did not give side products. A brief discussion on the biological activities of some heterocycles is also provided.

Pyrimido[1,2-a]benzimidazoles: synthesis and perspective of their pharmacological use

The review presents data on the synthesis as well as studies of biological activity of new derivatives of pyrimido[1,2-a]benzimidazoles published over the last decade. The bibliography of the review includes 136 sources.

Design, synthesis and anticancer/antiestrogenic activities of novel indole-benzimidazoles

Indole-benzimidazoles have recently gained attention due to their antiproliferative and antiestrogenic effects. However, their structural similarities and molecular mechanisms shared with selective estrogen receptor modulators (SERMs) have not yet been investigated. In this study, we synthesized novel ethylsulfonyl indole-benzimidazole derivatives by substituting the first (R₁) and fifth (R₂) positions of benzimidazole and indole groups, respectively. Subsequently, we performed ¹H NMR, ¹³C NMR, and Mass spectral and in silico docking analyses, and anticancer activity screening studies of these novel indole-benzimidazoles. The antiproliferative effects of indole-benzimidazoles were found to be more similar between the estrogen (E2) responsive cell lines MCF-7 and HEPG2 in comparison to the Estrogen Receptor negative (ER-) cell line MDA-MB-231. R₁:p-fluorobenzyl group members were selected as lead compounds for their potent anticancer effects and moderate structural affinity to ER. Microarray expression profiling and gene enrichment analyses (GSEA) of the selected compounds (R₁:p-fluorobenzyl: 48, 49, 50, 51; R₁:3,4-difluorobenzyl: 53) helped determine the similarly modulated cellular signaling pathways among derivatives. Moreover, we identified known compounds that have significantly similar gene signatures to that of 51 via queries performed in LINCS database; and further transcriptomics comparisons were made using public GEO datasets (GSE35428, GSE7765, GSE62673). Our results strongly demonstrate that these novel indole-benzimidazoles can modulate ER target gene expression as well as dioxin-mediated aryl hydrocarbon receptor and amino acid deprivation-mediated integrated stress response signaling in a dose-dependent manner.

Design, synthesis and ADMET prediction of bis-benzimidazole as anticancer agent

A new series of bis-benzimidazole clubbed with primary amine (3i-iii) and aromatic aldehydes (4i-ix) were design and synthesize with an intention to search an anticancer lead compound under microwave irradiation in good yields. Further, the spectral characterization of synthetic compounds were done with modern instrumental techniques such as FTIR, NMR (¹H and ¹³C), MS and elemental analysis. Anticancer activities of synthesized compounds were investigated at National Cancer Institute (NCI) against NCI 60 cell line panel, results showed good to notable anticancer activity. With the help of molinspiration, drug like properties and bioactivity score for drug targets of synthetic compounds were predicted and found to obey the Lipinski's rule, result indicates that the derivatives are orally active molecules. Osiris property explorer was used for the prediction of drug relevant properties and toxicity of synthetic compounds. Pre ADMET and Lazar toxicity was also used to estimate ADME and toxicity of synthetic compounds. Two compounds, 4i [(Z)-2-((1H-benzo[d]imidazol-2-yl) methyl)-1-(1H-benzo[d]imidazol-2-yl)-3-(thiophen-2-yl) prop-2-en-1-one] and 4iii [(Z)-2-((1H-benzo[d]imidazol-2-yl) methyl)-1-(1H-benzo [d] imidazol-2-yl)-3-(1H-pyrrol-2-yl)prop-2-en-1-one] were exhibited highest drug score and emerged as lead compounds and motivates for further development of more effective and safer compounds.

Synthesis, Antioxidant and Antiurease Activities of Some New 5,6- dichloro-2-(4-fluorobenzyl)-1H-benzimidazole Derivatives Containing Furan, Oxadiazole, Triazole and Thiadiazole Moieties

Background:

Benzimidazoles and its derivatives have been attracting interest for many years because of their biological activities. Benzimidazoles containing different heterocyclic moieties have wide range of biological activities such as antimicrobial, antioxidant, anticancer, antiviral, etc.

Methods:

In this study, some benzimidazole derivatives containing furan, oxadiazole, triazole and thiadiazole moieties have been synthesized and then evaluated for their antioxidant and antiurease activities.

Results:

The results showed that all the tested benzimidazoles indicated remarkable urease inhibitory potentials with IC50 values ranging between 0.303±0.03 to 0.591±0.08 µM.

Conclusion:

In conclusion, synthesized benzimidazole derivatives showed good antioxidant and antiurease activities. Heterocyclic groups on benzimidazole nucleus enhance the activities.

Selective synthesis of (1H-benzo[d]imidazol-2-yl)(phenyl)methanone and quinoxaline from aromatic aldehyde and o-phenylenediamine

We have designed a general, inexpensive, and versatile method for the synthesis of (1H-benzo[d]imidazol-2-yl)(phenyl)methanone and the formation of C-N bonds via an aromatic aldehyde and o-phenylenediamine. In the presence of N,N-dimethylformamide/sulfur, (1H-benzo[d]imidazol-2-yl)(phenyl)methanone was obtained; however, in the absence of sulfur, quinoxaline was obtained in 1,4-dioxane. A wide range of quinoxalines and (1H-benzo[d]imidazol-2-yl)(phenyl)methanones was obtained under mild conditions.

Synthesis, characterization and biological evaluation of novel benzimidazole derivatives

In search of achieving less toxic and more potent chemotherapeutics, three novel heterocyclic benzimidazole derivatives: 2-(1H-benzo[d]imidazol-2-yl)-4-chlorophenol (BM1), 4-chloro-2-(6-methyl-1H-benzo[d]imidazol-2-yl)phenol (BM2) and 4-chloro-2-(6-nitro-1H-benzo[d]imidazol-2-yl)phenol (BM3) with DNA-targeting properties, were synthesized and fully characterized by important physicochemical techniques. The DNA binding properties of the compounds were investigated by UV-Visible absorption titrations and thermal denaturation experiments. These molecules exhibited a good binding propensity to fish sperm DNA (FS-DNA), as evident from the high binding constants (K_b) values: 1.9 × 10⁵, 1.39 × 10⁵ and 1.8 × 10⁴ M^‒1 for BM1, BM2 and BM3, respectively. Thermal melting studies of DNA further validated the absorption titration results and best interaction was manifested by BM1 with ΔT_m = 4.96 °C. The experimental DNA binding results were further validated theoretically by molecular docking study. It was confirmed that the molecules (BM1-BM3) bind to DNA via an intercalative and groove binding mode. The investigations showed a correlation between binding constants and energies obtained experimentally and through molecular docking, indicating a binding preference of benzimidazole derivatives with the minor groove of DNA. BM1 was the preferential candidate for DNA binding because of its flat structure, π-π interactions and less steric hindrance. To complement the DNA interaction, antimicrobial assays (antibacterial & antifungal) were performed. It was observed that compound BM2 showed promising activity against all bacterial strains (Micrococcus luteus, Staphylococcus aureus, Enterobacter aerogenes and Escherichia coli) and fungi (Aspergillus flavus, Aspergillus fumigatus and Fusarium solani), while rest of the compounds were active against selective strains. The MIC values of BM2 were found to be in the range of 12.5 ± 2.2-25 ± 1.5 µg/mL. Thus, the compound BM2 was found to be the effective DNA binding antimicrobial agent. Furthermore, the preliminary cytotoxic properties of synthesized compounds were evaluated by brine shrimps lethality assay to check their nontoxic nature towards healthy normal cells.Communicated by Ramaswamy H. Sarma.

New (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates as tubulin polymerization inhibitors

A series of new (3-(1H-benzo[d]imidazol-2-yl))/(3-(3H-imidazo[4,5-b]pyridin-2-yl))-(1H-indol-5-yl)(3,4,5-trimethoxyphenyl)methanone conjugates 4-6(a-i) were synthesized and evaluated for their antiproliferative activity on selected human cancer cell lines such as prostate (DU-145), lung (A549), cervical (HeLa) and breast (MCF-7). Most of these conjugates showed considerable cytotoxicity with IC₅₀ values ranging from 0.54 to 31.86 μM. Among them, compounds 5g and 6f showed significant activity against human prostate cancer cell line DU-145 with IC₅₀ values of 0.68 μM and 0.54 μM, respectively. Tubulin polymerization assay and immunofluorescence analysis results suggest that these compounds effectively inhibit microtubule assembly formation in DU-145. Further, the apoptosis-inducing ability of these derivatives (5g and 6f) was confirmed by Hoechst staining, measurement of mitochondrial membrane potential and ROS generation and annexin V-FITC assays.

Species-Specific Inactivation of Triosephosphate Isomerase from Trypanosoma brucei: Kinetic and Molecular Dynamics Studies

Human African Trypanosomiasis (HAT), a disease that provokes 2184 new cases a year in Sub-Saharan Africa, is caused by Trypanosoma brucei. Current treatments are limited, highly toxic, and parasite strains resistant to them are emerging. Therefore, there is an urgency to find new drugs against HAT. In this context, T. brucei depends on glycolysis as the unique source for ATP supply; therefore, the enzyme triosephosphate isomerase (TIM) is an attractive target for drug design. In the present work, three new benzimidazole derivatives were found as TbTIM inactivators (compounds 1, 2 and 3) with an I₅₀ value of 84, 82 and 73 µM, respectively. Kinetic analyses indicated that the three molecules were selective when tested against human TIM (HsTIM) activity. Additionally, to study their binding mode in TbTIM, we performed a 100 ns molecular dynamics simulation of TbTIM-inactivator complexes. Simulations showed that the binding of compounds disturbs the structure of the protein, affecting the conformations of important domains such as loop 6 and loop 8. In addition, the physicochemical and drug-like parameters showed by the three compounds suggest a good oral absorption. In conclusion, these molecules will serve as a guide to design more potent inactivators that could be used to obtain new drugs against HAT.

Design, synthesis and antimicrobial evaluation of pyrimidin-2-ol/thiol/amine analogues

Background

Pyrimidine is an aromatic heterocyclic moiety containing nitrogen atom at 1st and 3rd positions and play an important role to forms the central core for different necessity of biological active compounds, from this facts, we have designed and synthesized a new class of pyrimidin-2-ol/thiol/amine derivatives and screened for its in vitro antimicrobial activity.

Results and discussion

The synthesized pyrimidine derivatives were confirmed by IR, ¹H/¹³C-NMR, Mass spectral studies and evaluated for their in vitro antimicrobial potential against Gram positive (S. aureus and B. subtilis), Gram negative (E. coli, P. aeruginosa and S. enterica) bacterial strains and fungal strain (C. albicans and A. niger) by tube dilution method and recorded minimum inhibitory concentration in µM/ml. The MBC and MFC values represent the lowest concentration of compound that produces in the range of 96–98% end point reduction of the used test bacterial and fungal species.

Conclusion

In general all synthesized derivatives exhibited good antimicrobial activity. Among them, compounds 2, 5, 10, 11 and 12 have significant antimicrobial activity against used bacterial and fungal strains and also found to be more active than the standard drugs.Graphical abstract

Design and synthesis of novel phenyl -1, 4-beta-carboline-hybrid molecules as potential anticancer agents

A series of beta-carbolines with other heterocycles linked by phenyl ring has been designed and synthesized. The key intermediates 3 and 5 were synthesized by condensing tryptamine and teraldehyde via Pictet- Spengler method. All the newly synthesized compounds were tested for their anticancer activity against sixty human cell lines at NCI. The five dose results of compounds 3 and 7a showed enhancement of anticancer activity (GI₅₀ values range from 1.00 to 7.10 μM) against all the cell lines in comparison with some of earlier molecules. In addition to this protein binding and CT-DNA intercalation studies showed molecules are highly potential. The molecular docking studies, which support the multiple mode of interaction with DNA, moreover the synthesized compounds 3 and 7a are more potential and possess drug -like nature.

Functionalized Benzimidazole Scaffolds: Privileged Heterocycle for Drug Design in Therapeutic Medicine

Benzimidazole derivatives are crucial structural scaffolds found in diverse libraries of biologically active compounds which are therapeutically useful agents in drug discovery and medicinal research. They are structural isosteres of naturally occurring nucleotides, which allows them to interact with the biopolymers of living systems. Hence, there is a need to couple the latest information with the earlier documentations to understand the current status of the benzimidazole nucleus in medicinal chemistry research. This present work unveils the benzimidazole core as a multifunctional nucleus that serves as a resourceful tool of information for synthetic modifications of old existing candidates in order to tackle drug resistance bottlenecks in therapeutic medicine. This manuscript deals with the recent advances in the synthesis of benzimidazole derivatives, the widespread biological activities as well as pharmacokinetic reports. These present them as a toolbox for fighting infectious diseases and also make them excellent candidates for future drug design.

Synthesis and Biological Evaluation of 2-Aminobenzothiazole and Benzimidazole Analogs Based on the Clathrodin Structure

A series of 2-aminobenzothiazole and benzimidazole analogs based on the clathrodin scaffold was synthesized and investigated for their antimicrobial and antiproliferative activities as well as for their effects in hepatitis C virus (HCV) replicon model. Compound 7, derived from 2-aminobenzothiazole, exhibited moderate antimicrobial activity only against the Gram-positive bacterium, Enterococcus faecalis. In the antiviral assay, compounds 4d and 7 were found to suppress the HCV replicon by >70%, but also to exhibit cytotoxicity against the host cells (35 and 44%, respectively). Compounds 4a and 7 demonstrated good activity in the antiproliferative assays on the human melanoma cell line A-375. To assess the selectivity of the effects between cancerous and noncancerous cells, a mouse fibroblast cell line was used. The IC50 values for compound 7 against the melanoma cell line A-375 and the fibroblast cell line BALB/c 3T3 were 16 and 71 µM, respectively, yielding fourfold selectivity toward the cancer cell line. These results suggest that compound 7 should be studied further in order to fully explore its potential for drug development.

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a–aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 μM and 0.43 to 7.73 μM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 μM and 5l is 1.71 μM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

A novel benzimidazole derivative binds to the DNA minor groove and induces apoptosis in leukemic cells

In the present study, we have synthesized various benzimidazole derivatives, evaluated their potential to act as DNA minor groove binder and tested their chemotherapeutic efficacy.

Comprehensive Review in Current Developments of Benzimidazole-Based Medicinal Chemistry

The properties of benzimidazole and its derivatives have been studied over more than one hundred years. Benzimidazole derivatives are useful intermediates/subunits for the development of molecules of pharmaceutical or biological interest. Substituted benzimidazole derivatives have found applications in diverse therapeutic areas such as antiulcer, anticancer agents, and anthelmintic species to name just a few. This work systematically gives a comprehensive review in current developments of benzimidazole-based compounds in the whole range of medicinal chemistry as anticancer, antibacterial, antifungal, anti-inflammatory, analgesic agents, anti-HIV, antioxidant, anticonvulsant, antitubercular, antidiabetic, antileishmanial, antihistaminic, antimalarial agents, and other medicinal agents. This review will further be helpful for the researcher on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole drugs/compounds.

Structure activity relationship (SAR) study of benzimidazole scaffold for different biological activities: A mini-review

Benzimidazoles are the fused heterocyclic ring systems which form an integral part of vitamin B12 and have been luring many researchers all over the world to assess their potential therapeutic significance. They are known for their crucial role in numerous diseases via various mechanisms. Substitution of benzimidazole nucleus is a crucial step in the drug discovery process. Therefore, it is necessary to gather the latest information along with the earlier information to understand the present status of benzimidazole nucleus in drug discovery. In the present review, benzimidazole derivatives with different pharmacological activities are described on the basis of SAR study using structural substitution pattern around the benzimidazole nucleus and aims to review the reported work related to the chemistry and pharmacological activities of benzimidazole derivatives during recent years. The present manuscript to the best of our knowledge is the first compilation on synthesis and medicinal aspects including structure-activity relationships of benzimidazole reported to date.

Synthesis of β-carboline-benzimidazole conjugates using lanthanum nitrate as a catalyst and their biological evaluation

A series of β-carboline-benzimidazole conjugates bearing a substituted benzimidazole and an aryl ring at C3 and C1 respectively were designed and synthesized. The key step of their preparation was determined to involve condensation of substituted o-phenylenediamines with 1-(substituted phenyl)-9H-pyrido[3,4-b]indole-3-carbaldehyde using La(NO3)3·6H2O as a catalyst and their cytotoxic potential was evaluated. Conjugates 5a, 5d, 5h and 5r showed enhanced cytotoxic activity (GI50 values range from 0.3 to 7.1 μM in most of the human cancer cell lines) in comparison to some of the previously reported β-carboline derivatives. To substantiate the cytotoxic activity and to understand the nature of interaction of these conjugates with DNA, spectroscopy, DNA photocleavage and DNA topoisomerase I inhibition (topo-I) studies were performed. These conjugates (5a, 5d and 5r) effectively cleave pBR322 plasmid DNA in the presence of UV light. In addition, the effect of these conjugates on DNA Topo I inhibition was studied. The mode of binding of these new conjugates with DNA was also examined by using both biophysical as well as molecular docking studies, which supported their multiple modes of interaction with DNA. Moreover, an in silico study of these β-carboline-benzimidazole conjugates reveals that they possess drug-like properties.

Benzimidazole bearing oxadiazole and triazolo-thiadiazoles nucleus: design and synthesis as anticancer agents

Two new series of benzimidazole bearing oxadiazole[1-(1H-benzo[d]imidazol-2-yl)-3-(5-substituted-1,3,4-oxadiazol-2-yl)propan-1-ones (4a-l)] and triazolo-thiadiazoles[1-(1H-benzo[d]imidazol-2-yl)-3-(6-(substituted)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)propan-1-one (7a-e)] have been synthesized successfully from 4-(1H-benzo[d]imidazol-2-yl)-4-oxobutanehydrazide (3) with an aim to produce promising anticancer agents. In vitro anticancer activities of synthesized compounds were screened at the National Cancer Institute (NCI), USA, according to their applied protocol against full NCI 60 human cell lines panel; results showed good to remarkable anticancer activity. Among them, compound (4j, NCS: 761980) exhibited significant growth inhibition and further screened at 10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10 and 100 μM) with GI(50) values ranging from 0.49 to 48.0 μM and found superior for the non-small cell lung cancer cell lines like HOP-92 (GI(50) 0.49, TGI 19.9,LC(50) >100 and Log(10)GI(50) -6.30, Log(10)TGI -4.70, Log(10)LC(50) >-4.00).

Benzimidazole clubbed with triazolo-thiadiazoles and triazolo-thiadiazines: new anticancer agents

Two series of Benzimidazole clubbed with triazolo-thiadiazoles (5a-q, 5r, 5s and 5x-a(1)) and triazolo-thiadiazines (5t-w) were synthesized with an aim to produce promising anticancer agents. In vitro anticancer activities of synthesized compounds were investigated at the National Cancer Institute (NCI) against NCI 60 cell line panel; results showed good to remarkable broad-spectrum anticancer activity. Among them, the compound 5h (NCS: 760452, 1-(1H-benzo [d] imidazol-2-yl)-3-(6-(2,4-dichlorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl) propan-1-one) exhibited significant growth inhibition with GI50 values ranging from 0.20 to 2.58 μM and found superior selectivity for the leukemia cell lines and further screened at 10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10 and 100 μM). The 5h may possibly be used as lead compound for developing new anticancer agents.

High-throughput-screening-based identification and structure-activity relationship characterization defined (S)-2-(1-aminoisobutyl)-1-(3-chlorobenzyl)benzimidazole as a highly antimycotic agent nontoxic to cell lines

Novel nontoxic (S)-2-aminoalkylbenzimidazole derivatives were found to be effective against Candida spp. at low micromolar concentrations using high-throughput screening with infected HeLa cells. A collection of analogues defined the chemical groups relevant for activity. The most active compound was characterized by transcriptional analysis of the response of C. albicans Sc5314. (S)-2-(1-Aminoisobutyl)-1-(3-chlorobenzyl)benzimidazole had a strong impact on membrane biosynthesis. Testing different clinically relevant pathogenic fungi showed the selectivity of the antimycotic activity against Candida species.

A screening assay based on host-pathogen interaction models identifies a set of novel antifungal benzimidazole derivatives

Fungal infections are a serious health problem in clinics, especially in the immune-compromised patient. Disease ranges from widespread superficial infections like vulvovaginal infections to life-threatening systemic candidiasis. Especially for systemic mycoses, only a limited arsenal of antifungals is available. The most commonly used classes of antifungal compounds used include azoles, polyenes, and echinocandins. Due to emerging resistance to standard therapy, significant side effects, and high costs for several antifungals, there is a medical need for new antifungals in the clinic and general practice. In order to expand the arsenal of compounds with antifungal activities, we screened a compound library including more than 35,000 individual compounds derived from organic synthesis as well as combinatorial compound collections representing mixtures of compounds for antimycotic activity. In total, more than 100,000 compounds were screened using a new type of activity-selectivity assay, analyzing both the antifungal activity and the compatibility with human cells at the same time. One promising hit, an (S)-2-aminoalkyl benzimidazole derivative, was developed among a series of lead compounds showing potent antifungal activity. (S)-2-(1-Aminoisobutyl)-1-(3-chlorobenzyl) benzimidazole showed the highest antifungal activity and the best compatibility with human cells in several cell culture models and against a number of clinical isolates of several species of pathogenic Candida yeasts. Transcriptional profiling indicates that the newly discovered compound is a potential inhibitor of the ergosterol pathway, in contrast to other benzimidazole derivatives, which target microtubules.