Benzimidazole derivatives: Spectrum of pharmacological activity and toxicological properties (a review)

Synthesis and Tyrosinase Inhibitory Activity of Novel Benzimidazole/Thiazolidin-4-one Hybrid Derivatives

In this study, novel 3-(phenylamino)thiazolidin-4-one 2 a-d and 3-(phenyl)thiazolidin-4-one 3 a-g derivatives which are having benzimidazole moiety were synthesized and their tyrosinase inhibitory activity were investigated. The structures of the target compounds were elucidated using 1 H/13 C-NMR, IR and MS. The structure of 2 b was also characterized using HSQC NMR technique. Among the target compounds, 3 b-g demonstrated stronger tyrosinase inhibitory activity (IC50 values for 3 b-g ranged from 80.93 to 119.20 μM), compared to the positive control kojic acid (IC50 : 125.08 μM). With IC50 value of 80.93 μM, 5-(2-(4-(1H-benzimidazol-1-yl)phenyl)-4-oxothiazolidin-3-yl)-2-methylbenzenesulfonamide 3 g was found to be the most active derivative of the series. Molecular docking studies were conducted to elucidate the binding interactions between compounds and tyrosinase. The MTT assay studies used to determine the cytotoxicity of 3 b-g showed that 3 c, 3 d, 3 f and 3 g were not cytotoxic in the range of 0-200 μM. Considering its tyrosinase inhibitory activity and cytotoxic effect, 3 g exhibits promising potential for further research and development as a novel tyrosinase inhibitor.

Crystal structure and Hirshfeld surface analysis of a new benzimidazole compound, 3-{1-[(2-hy-droxyphen-yl)meth-yl]-1H-1,3-benzo-diazol-2-yl}phenol

The title compound, C20H16N2O2, is composed of two monosubstituted benzene rings and one benzimidazole unit. The benzimidazole moiety subtends dihedral angles of 46.16 (7) and 77.45 (8)° with the benzene rings, which themselves form a dihedral angle of 54.34 (9)°. The crystal structure features O-H⋯N and O-H⋯O hydrogen-bonding inter-actions, which together lead to the formation of two-dimensional hydrogen-bonded layers parallel to the (101) plane. In addition, π-π inter-actions also contribute to the crystal cohesion. Hirshfeld surface analysis indicates that the most significant contacts in the crystal packing are: H⋯H (47.5%), O⋯H/H⋯O (12.4%), N⋯H/H⋯N (6.1%), C⋯H/H⋯C (27.6%) and C⋯C (4.6%).

Design, synthesis, antimicrobial activity and molecular docking study of cationic bis-benzimidazole-silver(I) complexes

Two series of bis(1-alkylbenzimidazole)silver(I) nitrate and bis(1-alkyl-5,6-dimethylbenzimidazole)silver(I) nitrate complexes, in which the alkyl substituent is either an allyl, a 2-methylallyl, an isopropyl or a 3-methyloxetan-3-yl-methyl chain, were synthesized and fully characterized. The eight N-coordinated silver(I) complexes were screened for both antimicrobial activities against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus, Staphylococcus aureus MRSA, and Enterococcus faecalis) bacteria and antifungal activities against Candida albicans and Candida glabrata strains. Moderate minimal inhibitory concentrations (MIC) of 0.087 μmol/mL were found when the Gram-negative and Gram-positive bacteria were treated with the silver complexes. Nevertheless, MIC values of 0.011 μmol/mL, twice lower than for the well-known fluconazole, against the two fungi were measured. In addition, molecular docking was carried out with the structure of Escherichia coli DNA gyrase and CYP51 from the pathogen Candida glabrata with the eight organometallic complexes, and molecular reactivity descriptors were calculated with the density functional theory-based calculation methods.

The coenzyme B12 precursor 5,6-dimethylbenzimidazole is a flavin antagonist in Salmonella

Salmonella enterica subsp. enterica sv. Typhimurium str. LT2 (hereafter S. Typhimurium) synthesizes adenosylcobalamin (AdoCbl, CoB12) de novo only under anoxic conditions, but it can assemble the lower ligand loop (a.k.a. the nucleotide loop) and can form the unique C-Co bond present in CoB12 in the presence or absence of molecular oxygen. During studies of nucleotide loop assembly in S. Typhimurium, we noticed that the growth of this bacterium could be arrested by the lower ligand nucleobase, namely 5,6-dimethylbenzimidazole (DMB). Here we report in vitro and in vivo evidence that shows that the structural similarity of DMB to the isoalloxazine moiety of flavin cofactors causes its deleterious effect on cell growth. We studied DMB inhibition of the housekeeping flavin dehydrogenase (Fre) and three flavoenzymes that initiate the catabolism of tricarballylate, succinate or D-alanine in S. Typhimurium. Notably, while growth with tricarballylate was inhibited by 5-methyl-benzimidazole (5-Me-Bza) and DMB, growth with succinate or glycerol was arrested by DMB but not by 5-Me-Bza. Neither unsubstituted benzimidazole nor adenine inhibited growth of S. Typhimurium at DMB inhibitory concentrations. Whole genome sequencing analysis of spontaneous mutant strains that grew in the presence of inhibitory concentrations of DMB identified mutations effecting the cycA (encodes D-Ala/D-Ser transporter) and dctA (encodes dicarboxylate transporter) genes and in the coding sequence of the tricarballylate transporter (TcuC), suggesting that increased uptake of substrates relieved DMB inhibition. We discuss two possible mechanisms of inhibition by DMB.

Surface-enhanced Raman spectroscopy for studying the interaction of N-propyl substituted imidazole compound with salmon sperm DNA

BACKGROUND

Surface Enhanced Raman Spectroscopy (SERS) is a very promising and fast technique for studying drugs and for detecting chemical nature of a molecule and DNA interaction. In the current study, SERS is employed to check the interaction of different concentrations of n-propyl imidazole derivative ligand with salmon sperm DNA using silver nanoparticles as SERS substrates.

OBJECTIVES

Multivariate data analysis technique like principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) are employed for the detailed analysis of the SERS spectral features associated with the mode of action of the imidazole derivative ligand with DNA.

METHODOLOGY

Silver nanoparticles were used as a SERS substrate in DNA-drug interaction. Five different concentrations of ligands were interacted with DNA and mix with Ag-NPs as substrate. The SERS spectra of were acquired for all seven samples and processed using MATLAB. Additionally, PCA and PLS-DA were used to assessed the ability SERS to differentiate interaction of DNA-drug.

RESULTS

Differentiating SERS features having changes in their peak position and intensities are observed including 629, 655, 791, 807, 859, 1337, 1377 and 1456 cm^-1. These SERS features reveal that binding of ligand with DNA is electrostatic in nature, and have specificity to major groove where it forms GC-CG interstrand cross-linking with the DNA double helix.

CONCLUSIONS

SERS give significant information regarding to Drug-DNA interaction mechanism, SERS spectra inferred the mode of action of anticancer compound that are imidazole in nature.

One-pot Synthesis of Substituted Benzimidazole Derivatives under Ultrasonic Irradiation Using ZnFe2O4 Reusable Catalyst

Herein, an efficient one-pot synthesis is described, of substituted benzimidazole derivatives (3a-j) from a condensation of various o-phenylenediamine (1a-j) aromatic aldehyde (2a-j) using ZnFe2O4 as a nano-catalyst under ultrasonic irradiation conditions. All forms of aldehydes with an electron releasing or electron –withdrawing substituent have a significant yield. The catalyst can easily be recovered after completion of the reaction and reused without affecting its activity. Prepared benzimidazole derivatives showed moderate to good anti-tuberculosis results.

Synthesis of Novel Benzimidazole-Based Thiazole Derivatives as Multipotent Inhibitors of α-Amylase and α-Glucosidase: In Vitro Evaluation along with Molecular Docking Study

In this study, hybrid analogs of benzimidazole containing a thiazole moiety (1-17) were afforded and then tested for their ability to inhibit α-amylase and α-glucosidase when compared to acarbose as a standard drug. The recently available analogs showed a wide variety of inhibitory potentials that ranged between 1.31 ± 0.05 and 38.60 ± 0.70 µM (against α-amylase) and between 2.71 ± 0.10 and 42.31 ± 0.70 µM (against α-glucosidase) under the positive control of acarbose (IC₅₀ = 10.30 ± 0.20 µM against α-amylase) (IC₅₀ = 9.80 ± 0.20 µM against α-glucosidase). A structure-activity relationship (SAR) study was carried out for all analogs based on substitution patterns around both rings B and C respectively. It was concluded from the SAR study that analogs bearing either substituent(s) of smaller size (-F and Cl) or substituent(s) capable of forming hydrogen bonding (-OH) with the catalytic residues of targeted enzymes enhanced the inhibitory potentials. Therefore, analogs 2 (bearing meta-fluoro substitution), 3 (having para-fluoro substitution) and 4 (with ortho-fluoro group) showed enhanced potency when evaluated against standard acarbose drug with IC₅₀ values of 4.10 ± 0.10, 1.30 ± 0.05 and 1.90 ± 0.10 (against α-amylase) and 5.60 ± 0.10, 2.70 ± 0.10 and 2.90 ± 0.10 µM (against α-glucosidase), correspondingly. On the other hand, analogs bearing substituent(s) of either a bulky nature (-Br) or that are incapable of forming hydrogen bonds (-CH₃) were found to lower the inhibitory potentials. In order to investigate the binding sites for synthetic analogs and how they interact with the active areas of both targeted enzymes, molecular docking studies were also conducted on the potent analogs. The results showed that these analogs adopted many important interactions with the active areas of enzymes. The precise structure of the newly synthesized compounds was confirmed using several spectroscopic techniques as NMR and HREI-MS.

Multipotent Cholinesterase Inhibitors for the Treatment of Alzheimer's Disease: Synthesis, Biological Analysis and Molecular Docking Study of Benzimidazole-Based Thiazole Derivatives

Twenty-four analogues of benzimidazole-based thiazoles (1-24) were synthesized and assessed for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory potential. All analogues were found to exhibit good inhibitory potential against cholinesterase enzymes, having IC50 values in the ranges of 0.10 ± 0.05 to 11.10 ± 0.30 µM (for AChE) and 0.20 ± 0.050 µM to 14.20 ± 0.10 µM (for BuChE) as compared to the standard drug Donepezil (IC50 = 2.16 ± 0.12 and 4.5 ± 0.11 µM, respectively). Among the series, analogues 16 and 21 were found to be the most potent inhibitors of AChE and BuChE enzymes. The number (s), types, electron-donating or -withdrawing effects and position of the substituent(s) on the both phenyl rings B & C were the primary determinants of the structure-activity relationship (SAR). In order to understand how the most active derivatives interact with the amino acids in the active site of the enzyme, molecular docking studies were conducted. The results obtained supported the experimental data. Additionally, the structures of all newly synthesized compounds were elucidated by using several spectroscopic methods like 13C-NMR, 1H-NMR and HR EIMS.

Docking study, molecular dynamic, synthesis, anti-α-glucosidase assessment, and ADMET prediction of new benzimidazole-Schiff base derivatives

The control of postprandial hyperglycemia is an important target in the treatment of type 2 diabetes mellitus (T2DM). As a result, targeting α-glucosidase as the most important enzyme in the breakdown of carbohydrates to glucose that leads to an increase in postprandial hyperglycemia is one of the treatment processes of T2DM. In the present work, a new class of benzimidazole-Schiff base hybrids 8a–p has been developed based on the potent reported α-glucosidase inhibitors. These compounds were synthesized by sample recantations, characterized by ¹H-NMR, ¹³C-NMR, FT-IR, and CHNS elemental analysis, and evaluated against α-glucosidase. All new compounds, with the exception of inactive compound 8g, showed excellent inhibitory activities (60.1 ± 3.6–287.1 ± 7.4 µM) in comparison to acarbose as the positive control (750.0 ± 10.5). Kinetic study of the most potent compound 8p showed a competitive type of inhibition (K_i value = 60 µM). In silico induced fit docking and molecular dynamics studies were performed to further investigate the interaction, orientation, and conformation of the title new compounds over the active site of α-glucosidase. In silico druglikeness analysis and ADMET prediction of the most potent compounds demonstrated that these compounds were druglikeness and had satisfactory ADMET profile.

AlCl3-Mediated CHF2 Transfer and Cyclocondensation of Difluoromethoxy Functionalized o-Phenylenediamines to Access N-Substituted Benzimidazoles

Herein, we report for the first time a transition-metal-free frustrated Lewis pair (FLP) catalyzed CHF₂ group migration from an oxygen atom to the neighboring nitrogen atom, which led to the synthesis of N-substituted benzimidazoles at room temperature with excellent yields, broad functional group tolerance, and a short reaction time. The oxygen-attached difluoromethane acted as a C1 source in the synthesis of N-substituted benzimidazoles in the presence of AlCl₃ by cleaving one C-O bond and two C-F bonds, resulting in formation of two new C-N bonds.

Teaching an old dog new tricks: The case of Fenbendazole

The objective of this study is the assessment of the cytotoxic effect of fenbendazole and its commercially available formulation, which is used for its antihelmintic properties. The formulation was tested for its efficacy as well as the determination of the ingredients with proliferation assays and analytical techniques. HPLC, LC-MS and NMR confirmed the stated amount of active ingredient on the label. Dissolution studies were performed to simulate the ability of fenbendazole to dissolve adequately in the fluids of the Gastrointestinal tract, be absorbed in the circulation and reach certain areas of the human body. However, dissolution studies showed that both brands possess issues in their distribution. The in vitro drug screening exhibited potential cytotoxic effect in different types of human cancer cell lines and MDA-MB-231 human breast adenocarcinoma cells appeared to be the most sensitive with IC₅₀ value lower than 10 μM.

Synthesis, characterization and in vitro, in vivo, in silico biological evaluations of substituted benzimidazole derivatives

A series of substituted benzimidazole derivatives were synthesized by reacting O-phenylenediamine with various aromatic aldehydes or glycolic acid using various inexpensive reagents in aqueous media. Synthesized compounds were characterized and elucidated by IR, ¹H NMR, ESI-MS spectra. Resultant compounds were screened for in vitro antimicrobial, cytotoxic, antioxidant, lipid peroxidation and cholinesterase inhibitory activities, in vivo analgesic and anti-inflammatory, and in silico anti-acetylcholinesterase and anti-butyrylcholinesterase activities. Among the synthesized compounds, compound 3b showed most promising central analgesic effect (46.15%) compared to morphine (48.08%), whereas compounds 6, 3c and 3a showed significant peripheral analgesic activity at two different dose levels (25 mg/kg and 50 mg/kg). Compounds 3b and 3a at the dose of 100 mg/kg showed significant anti-inflammatory effects from the first hour and onward, whereas compounds 6 and 3b showed moderate cytotoxic activities. In addition, compound 3a showed significant antioxidant activity having IC₅₀ value of 16.73 µg/ml compared to 14.44 µg/ml for the standard BHT. Compound 6, 3a and 3b exhibited mild to moderate cholinesterase inhibitory activity. In silico studies revealed that compound 3a and 3b might be suitable for cholinesterase inhibitory activity. A comprehensive computational and experimental data suggested compounds 3b and 3a as the best possible candidates for pharmacological activity. All the experimental data were statistically significant (p < 0.01 level).

Agro-waste sourced catalyst as an eco-friendly and sustainable approach for Knoevenagel condensation reaction

Background:

The present work describes an eco-friendly and sustainable approach for the Knoevenagel condensation of an aromatic aldehyde with ethyl cyanoacetate, and salicylaldehyde with Meldrum acid for the synthesis of ethyl benzylidenecyanoacetate and 3-carboxy coumarin (2-oxo-2H-1-benzopyran) derivatives, respectively. The reaction performed under greener catalytic media Water Extract of Watermelon Fruit Peel Ash (WEWFPA) is an eco-friendly protocol derived from the agro-waste feedstock. Various protocols have been reported for the synthesis of Knoevenagel condensation reaction using a hazardous catalyst or/and solvent found toxic to the environment, reaction time longer, poor yield, and required purification of the final product. The present method provides several added advantages of being completely greener, economic, giving high yield, inexpensive catalyst, and the final product isolated in pure form with good yield.

Objective:

The objective of the study was to develop a green methodology for the synthesis of ethyl benzylidenecyanoacetate and 3-carboxy coumarin derivatives.

Results:

The agro-waste based catalyst developed avoids the use of external inorganic/organic base, additives, and solvent-free synthesis of Knoevenagel condensation of ethyl benzylidenecyanoacetate and 3-carboxy coumarin derivatives under rt and microwave irradiation, respectively described. The microwave irradiation condition requires less time for the completion of the reaction and also gave better yield isolation

Methods:

We have demonstrated WEWFPA as a greener homogenous agro-waste is employed under rt stirring and microwave irradiation for the economic synthesis of ethyl benzylidenecyanoacetate and 3-carboxy coumarin derivatives. The developed method was found robust, non-hazardous and solvent-free with simple work-up gave target product.

Conclusion:

In conclusion, we have established an efficient, simple, agro-waste based catalytic approach for the synthesis of ethylbenzylidenecyanoacetate and 3-carboxy coumarin derivatives employing WEWFPA as an efficient catalyst under rt stirring and microwave synthesis, respectively. The method is a greener, economical and eco-friendly approach for the synthesis of Knoevenagel condensation products. The advantages of the present approach are solvent-free, no external metal, chemical base free, short reaction time and isolated product in good to excellent yields. The catalyst is agro-waste derived, which has abundant in natural sources, thus making the present approach a greener one.

Ultrasound-Promoted Sustainable Synthesis and Antimicrobial Evaluation of 2-Aryl Benzimidazoles Catalyzed by BPAE at Room Temperature

Background:

Present-day chemists are more interested in developing and using green chemistry protocol for various organic transformations, which employ natural feedstock extracts, and solvent-free, and greener catalysts; they are well known for their non-hazardous nature and have replaced many organic and inorganic based catalysts. In literature, the reported homogenous catalytic approaches have been employed for various bioactive heterocycle syntheses, which follow the green chemistry principle established for various organic transformations catalyzed by WERSA, BFE, WEPPA, WEMFSA, WEMPA, and Eichhorniacrassipes. Among them, 2-aryl benzimidazole derivatives have emerged as prominent molecules with a wide variety of applications in biological and material science.

Methods:

The agro-waste sourced from the banana peel is utilized for the preparation of BPAE catalyst, which is employed for the synthesis of 2-aryl benzimidazole derivatives under ultrasound waves at room temperature.

Results:

Here, 2-Aryl benzimidazoles synthesized through the reaction of a substituted o-phenylene diamine with substituted benzoyl chloride catalyzed by BPAE under ultrasound waves at room temperature are described. Furthermore, catalyst BPAE is characterized by flame emission spectrometry, SEM-EDX, and XRD techniques.

Conclusion:

The present work established an eco-friendly, sustainable and novel approach for the synthesis of 2-aryl benzimidazoles using natural feedstock BPAE. The major merits of BPAE include its use as an agro-waste-derived catalyst. It is also highly abundant, inexpensive, yields faster reactions, has a simple workup, and does not require the use of column chromatography.

Ultrastructural changes in methicillin-resistant Staphylococcus aureus (MRSA) induced by metabolites of thermophilous fungi Acrophialophora levis

Staphylococcus aureus and Methicillin-resistant S. aureus (MRSA) remains one of the major concerns of healthcare associated and community-onset infections worldwide. The number of cases of treatment failure for infections associated with resistant bacteria is on the rise, due to the decreasing efficacy of current antibiotics. Notably, Acrophialophora levis, a thermophilous fungus species, showed antibacterial activity, namely against S. aureus and clinical MRSA strains. The ethyl acetate extract of culture filtrate was found to display significant activity against S. aureus and MRSA with a minimum inhibitory concentration (MIC) of 1 μg/mL and 4 μg/mL, respectively. Scanning electron micrographs demonstrated drastic changes in the cellular architecture of metabolite treated cells of S. aureus and an MRSA clinical isolate. Cell wall disruption, membrane lysis and probable leakage of cytoplasmic are hallmarks of the antibacterial effect of fungal metabolites against MRSA. The ethyl acetate extract also showed strong antioxidant activity using two different complementary free radicals scavenging methods, DPPH and ABTS with efficiency of 55% and 47% at 1 mg/mL, respectively. The total phenolic and flavonoid content was found to be 50 mg/GAE and 20 mg/CAE, respectively. More than ten metabolites from different classes were identified: phenolic acids, phenylpropanoids, sesquiterpenes, tannins, lignans and flavonoids. In conclusion, the significant antibacterial activity renders this fungal strain as a bioresource for natural compounds an interesting alternative against resistant bacteria.

Synthesis, Characterization and Antimicrobial Evaluation of Some N-Substituted Benzimidazole Derivatives

BACKGROUND

Due to the appearance of communicable microbial diseases and the toxicity related with presently used several antimicrobials such as β-lactam antibiotics, tetracyclines, quinolones, macrolides, glycopeptides (vancomycin) etc, demand for new antimicrobial agents has become a great concern in new technologies to improve efficacy and safety.

METHODS

In search of new antimicrobial agents with higher potency, some N-substituted benzimidazole derivatives (4, 5a-5h & 6) were obtained by chloroacetylation of benzimidazole followed by reaction with different amines, which were characterized by spectroscopic methods. All the target compounds were evaluated for their antibacterial and antifungal activity against microorganisms using two-fold serial dilution method.

RESULTS

Among the compounds evaluated, compounds 4 and 5d exhibited potent activity against Bacillus thuringiensis and Candida albicans while showed moderate activity against Escherischia coli when compared to amoxicillin and fluconazole. Compound 5a showed significant activity against tested microorganisms.

CONCLUSION

From the current study, it may be concluded that synthesized compounds are fulfilling in terms of their structural distinctiveness and marked biological properties. These compounds might be encouraged to initiate a new class of antimicrobial agents.

Biomimetic hydrogenation of electron deficient olefins using in situ generated 2-arylbenzimidazoline: synthesis of novel 3-benzylbenzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones

In the present study, 2-Arylbenzimidazoline generated in situ from reaction of aromatic aldehydes and o-phenylenediamine used as biomimetic reductive agents for reductive alkylation of 2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one for synthesis of novel 3-benzyl-2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones is described. The main benefits of this protocol include simplicity, reaction mildness, high yield, easy work up, and simple purification. The molecular structures were characterized by IR spectrophotometry, mass spectrometry, NMR spectroscopy, and elemental analysis.

Benzimidazole based hybrids against complex diseases: A catalogue of the SAR profile

The fused heterocyclic ring system has been recognized as a privileged structure that is used as a template in medicinal chemistry for drug discovery. Benzimidazole is one of the common scaffolds found in several natural products such as histidine, purines, and an integral part of vitamin B12. This hetero-aromatic bicyclic ring system acts as a pharmacophore in various drugs of therapeutic interest and has a broad spectrum of activity. Literature reports suggest that diversely substituted benzimidazoles possess distinct pharmacological profiles with multi-targeting potential, thereby, an indispensable anchor for the development of novel therapeutic agents against complex diseases such as cancer, malaria, inflammatory disorders, microbial diseases, hypertension, etc. Thus, lots of efforts have been diverted towards exploring the therapeutic potential of benzimidazoles. Despite great efforts made by the research community, still, some multi-factorial diseases continue to progress due to their complex pathophysiology. Under these sets of circumstances, there is a need to explore this nucleus for hybrid designing with multi-targeting potential against complex diseases. Benzimidazole-based hybrids have been reported to treat multifactorial diseases, making it a scaffold of interest for various pharmaceutical companies and research groups. In this write-up, we shed light on the recent pharmacological profiles, various designing strategies, and structure-activity relationships (SAR) of different benzimidazole-based hybrids.

A Five-Coordinate Copper(II) Complex Constructed from Sterically Hindered 4-Chlorobenzoate and Benzimidazole: Synthesis, Crystal Structure, Hirshfeld Surface Analysis, DFT, Docking Studies and Antibacterial Activity

A new CuII complex (1) was synthesized by reacting 4-chlorobenzoic acid, benzimidazole and metal salt using ethanol–water (1:1 v/v) as a solvent at room temperature. The complex was characterized by single-crystal X-ray analysis, FTIR and UV—vis spectroscopy. A distorted square pyramidal geometry of the CuII center was observed from the single-crystal X-ray study, which also revealed that the uncoordinated oxygen atom of the carboxylate anions forms intermolecular hydrogen bonds with the N–H groups of the benzimidazole ligands. The Hirshfeld analysis results revealed that the molecular packing of 1 is mainly controlled by O...H (12.7%), Cl...H (16.4%), C...H (24.4%) and H...H (31.1%) contacts. Density functional theory (DFT) calculations were performed to compute the HOMO–LUMO energy gap and electrostatic potential map for the charge transfer regions within the molecule and identify the possible electrophilic and nucleophilic regions of the molecule. A number of reactivity parameters calculated on the basis of EHOMO and ELUMO show its significant polarizability and reactive nature. Complex 1 was also examined and screened for its potential antibacterial effect using the agar well diffusion method. The newly synthesized complex showed an effective and higher killing rate of the microbes in antibacterial testing compared to the parent ligand. The CuII complex (1) showed an enhanced inhibitory activity against P. aeruginosa and equally demonstrated greater binding affinity with DNA gyrase (1KIJ) compared to its ligands according to the molecular docking studies.

Novel Benzimidazole Derivatives: Cytotoxic and Apoptotic Properties on Lung Cancer Cell Line

Background:

Benzimidazole derivatives are privileged molecules known to have a wide variety of biological activities. In medicinal chemistry, due to the ring’s structural similarity to nucleotides, its derivatives were investigated as new chemotherapeutic agents. Our research group have been studying 1,2-disubstituted benzimidazoles, including thiocarbamoyl group and their potential anticancer activity. Based on previous findings, we synthesized novel 1-[2-(4-substituted phenyl-2-oxoethyl)]-2-[(2/3/4-substituted phenylpiperidin-1-yl)thiocarbamoyl]benzimidazole derivatives (3a-o).

Methods:

The obtained fifteen derivatives were studied on A549 adenocarcinomic human alveolar basal epithelial cell line and mouse L929 fibroblastic cell line to determine their cytotoxic activity. These compounds were also investigated to identify their apoptotic properties.

Results and Discussion:

The structures of the compounds based on three different groups differ from each other with the phenyl substituents bonded to the piperazine ring. All of the compounds showed remarkable antitumor activity, but the first five compounds bearing non-substituted phenyl moiety exhibited selective cytotoxicity when compared in terms of potencies to the normal cell line.

Conclusion:

Compounds 3j, 3m and 3n were identified as the most apoptotic derivatives; however, compounds 3e and 3h provoked apoptosis with the percentages of 10.6 and 10.9% and selective cytotoxicity.

Head-to-head bisbenzazole derivatives as antiproliferative agents: design, synthesis, in vitro activity, and SAR analysis

In the present work, a series of bisbenzazole derivatives were designed and synthesized as antiproliferative agents. The antiproliferative activity of these compounds was investigated using MTT assay. Bisbenzazole derivatives showed significant antiproliferative activity against all the four tested cancer cell lines. Among the various bisbenzazole derivatives, bisbenzoxazole derivatives exhibited the most promising anticancer activity followed by bisbenzimidazole and bisbenzothiazole derivatives. All the derivatives were found to be less toxic as compared to methotrexate (positive control) in normal human cells, indicating selective and efficient antiproliferative activity of these bisbenzazole derivatives. The structure-activity relationships of heteroaromatic systems and linkers present in bisbenzazole derivatives were analyzed in detail. In silico ADMET prediction revealed that bisbenzazole is a drug-like small molecule with a favorable safety profile. Compound 31 is a potential antiproliferative hit compound that exhibits unique cytotoxic activity distinct from methotrexate. Twenty-one bisbenzoxazole derivatives have been designed synthesized and evaluated to be an antiproliferative activity against four human tumor cell lines.

Novel Mixed Complexes Derived from Benzoimidazolphenylethanamine and 4-(Benzoimidazol-2-yl)aniline: Synthesis, Characterization, Antibacterial Evaluation and Theoretical Prediction of Toxicity

Benzoimidazolphenylethanamine (BPE) has been synthesized using condensation reaction from o-phenyldiamine and L-phenylalanine. Some metal complexes have been synthesized from 4-(benzoimidazol-2-yl)aniline, benzoimidazolylphenylethanamine and cadmium(II), tin(II), copper(II) and nickel(II) metal in a molar ratio (1:1:1). All new metal complexes were characterized by spectroscopic data of FTIR, UV-visible electronic absorption, X-ray powder diffraction and thermal analysis. Spectra analysis of the mixed metal complexes showed the coordination of ligands to the metal ions via nitrogen atoms. The XRD powder showed that metal complexes have a monoclinic system. The preliminary tested in vitro antibacterial activities of Sn(II) complex was assayed against four bacterial isolates namely Micrococcus luteus, Staphylococcus aureus as Gram-positive, Pseudomonas aerugmosa and Escherichia coli.

Synthesis and insight into the structure–activity relationships of 2-phenylbenzimidazoles as prospective anticancer agents

Three series of 2-phenylbenzimidazoles obtained under simple and convenient pathways, were used to elucidate their SARs against three cancer cell lines: A549, MDA-MB-231 and PC3.

N-(tert-Butyl)-2-(2-nitrophenyl)imidazo[1,2-a]pyridin-3-amine

In the title compound, C17H18N4O2, the dihedral angle between the pyridine and benzene rings is 55.68 (11)°. In the crystal, N—H...N hydrogen bonds link the molecules into [010] chains.

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.

2-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxamide

2-(3,4-Dimethoxyphenyl)-N-(4-methoxyphenyl)-1-propyl-1H-benzo[d]imidazole-5-carboxamide was synthesized by the ‘one-pot’ reductive cyclization of N-(4-methoxyphenyl)-3-nitro-4-(propylamino)benzamide with 3,4-dimethoxybenzaldehyde, using sodium dithionite as a reductive cyclizing agent using DMSO as a solvent. The structure of newly synthesized compound was elucidated based on IR, 1H-NMR, 13C-NMR, and LC-MS data.

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.

Antimicrobial Potential of Benzimidazole Derived Molecules

Structural resemblance of benzimidazole nucleus with purine nucleus in nucleotides makes benzimidazole derivatives attractive ligands to interact with biopolymers of a living system. The most prominent benzimidazole compound in nature is N-ribosyldimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12. This structural similarity prompted medicinal chemists across the globe to synthesize a variety of benzimidazole derivatives and to screen those for various biological activities, such as anticancer, hormone antagonist, antiviral, anti-HIV, anthelmintic, antiprotozoal, antimicrobial, antihypertensive, anti-inflammatory, analgesic, anxiolytic, antiallergic, coagulant, anticoagulant, antioxidant and antidiabetic activities. Hence, benzimidazole nucleus is considered as a privileged structure in drug discovery, and it is exploited by many research groups to develop numerous compounds that are purported to be antimicrobial. Despite a large volume of research in this area, no novel benzimidazole derived compound has emerged as clinically effective antimicrobial drug. In the present review, we have compiled various reports on benzimidazole derived antimicrobials, classified as monosubstituted, disubstituted, trisubstituted and tetrasubstituted benzimidazoles, bisbenzimidazoles, fused-benzimidazoles, and benzimidazole derivative-metal complexes. The purpose is to collate these research reports, and to generate a generalised outlay of benzimidazole derived molecules that can assist the medicinal chemists in selecting appropriate combination of substituents around the nucleus for designing potent antimicrobials.

Design, synthesis and therapeutic potential of 3-(2-(1H-benzo[d]imidazol-2-ylthio)acetamido)-N-(substituted phenyl)benzamide analogues

Background

The emergence of bacterial resistance is a major public health problem. It is essential to develop and synthesize new therapeutic agents with better activity. The mode of actions of certain newly developed antimicrobial agents, however, exhibited very limited effect in treating life threatening systemic infections. Therefore, the advancement of multi-potent and efficient antimicrobial agents is crucial to overcome the increased multi-drug resistance of bacteria and fungi. Cancer, which remains as one of the primary causes of deaths and is commonly treated by chemotherapeutic agents, is also in need of novel and efficacious agents to treat resistant cases. As such, a sequence of novel substituted benzamides was designed, synthesized and evaluated for their antimicrobial and anticancer activities.

Methodology

All synthesized compounds were characterized by IR, NMR, Mass and elemental analysis followed by in vitro antimicrobial studies against Gram-positive (Staphylococcus aureus), Gram-negative (Salmonella typhi and Klebsiella pneumoniae) bacterial and fungal (Candida albicans and Aspergillus niger) strains by the tube dilution method. The in vitro anticancer evaluation was carried out against the human colorectal carcinoma cell line (HCT116), using the Sulforhodamine B assay.

Results, discussion and conclusion

Compound W6 (MIC_{sa, st, kp} = 5.19 µM) emerged as a significant antibacterial agent against all tested bacterial strains i.e. Gram-positive (S. aureus), Gram-negative (S. typhi, K. pneumoniae) while compound W1 (MIC_{ca, an} = 5.08 µM) was most potent against fungal strains (A. niger and C. albicans) and comparable to fluconazole (MIC = 8.16 µM). The anticancer screening demonstrated that compound W17 (IC₅₀ = 4.12 µM) was most potent amongst the synthesized  compounds and also more potent than the standard drug 5-FU (IC₅₀ = 7.69 µM).

Synthesis, Antibacterial, and Anti HepG2 Cell Line Human Hepatocyte Carcinoma Activity of Some New Potentially Benzimidazole-5-(Aryldiazenyl)Thiazole Derivatives

The paper describes the synthesis and biological evaluation of some new benzimidazole derivatives as potent clinical drugs that are useful in the treatment of some microbial infections and tumor inhibition. The starting compound 2-(bromomethyl)-1H-benzimidazole (1) was prepared, and hence underwent interesting functionalization reactions to afford several series of benzimidazole-5-(aryldiazenyl)thiazole derivatives: 3a⁻c, 7a⁻c, and 8a⁻c. The antibacterial activities of the synthesized compounds were evaluated by calculation of the inhibition zone diameter (mm) and the determination of minimum inhibitory concentration (µg/mL) against selected pathogenic bacteria Staphylococcus aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria).Noticeable efficiency was found based on in vitro screening for their antioxidant activity and cytotoxicity effect against the human liver cancer cell line (HepG2) and human hepatocyte carcinoma cells at relatively high concentrations.

Crystal structure and Hirshfeld surface analysis of two imidazo[1,2-a]pyridine derivatives: N-tert-butyl-2-(4-meth-oxy-phen-yl)-5-methyl-imidazo[1,2-a]pyridin-3-amine and N-tert-butyl-2-[4-(di-methyl-amino)-phen-yl]imidazo[1,2-a]pyridin-3-amine

In the title imidazo[1,2-a]pyridine derivatives, N-tert-butyl-2-(4-meth-oxy-phen-yl)-5-methyl-imidazo[1,2-a]pyridin-3-amine, C19H23N3O, (I), and N-tert-butyl-2-[4-(di-methyl-amino)-phen-yl]imidazo[1,2-a]pyridin-3-amine, C19H24N4, (II), the 4-meth-oxy-phenyl ring in (I) and the 4-(di-methyl-amino)-phenyl ring in (II) are inclined to the respective imidazole rings by 26.69 (9) and 31.35 (10)°. In the crystal of (I), mol-ecules are linked by N-H⋯N hydrogen bonds, forming chains propagating along the [001] direction. The chains are linked by C-H⋯π inter-actions, forming layers parallel to the (010) plane. In (II), the crystal packing also features N-H⋯N hydrogen bonds, which together with C-H⋯N hydrogen bonds link mol-ecules to form chains propagating along the c-axis direction. The chains are linked by C-H⋯π inter-actions to form layers parallel to the (100) plane. Inversion-related layers are linked by offset π-π inter-actions [inter-centroid distance = 3.577 (1) Å]. The inter-molecular inter-actions of both compounds were analyzed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Rh(III)-Catalyzed One-Pot Synthesis of Benzimidazoquinazolines via C-H Amidation-Cyclization of N-LG-2-phenylbenzoimidazoles

An efficient protocol to synthesize substituted benzo[4,5]imidazo[1,2- c]quinazolines starting from N-LG-2-phenylbenzoimidazole and dioxazolones catalyzed by Rh(III) or Ir(III) has been developed. Various substituted benzo[4,5]imidazo[1,2- c]quinazolines could be easily provided in up to 99% yield. A large range of substrates and functional groups are compatible for this transformation. This method features low catalyst loading, acid-free conditions, and low solvent consumption.