One-pot microwave assisted synthesis under green chemistry conditions, antioxidant screening, and cytotoxicity assessments of benzimidazole Schiff bases and pyrimido[1,2-a]benzimidazol-3(4H)-ones

Exploring the Synthetic and Antioxidant Potential of 1,2-Disubstituted Benzimidazoles Using [Et3NH][HSO4] Ionic Liquid Catalyst

An [Et3NH][HSO4] ionic-liquid catalyzed, intermolecular C-N bond formation for 1,2-disubstituted benzimidazole synthesis was achieved by the reaction of OPD and substituted aldehydes at ambient reaction conditions. Operational simplicity, use of easily available substrate and reagents, good yields (74-95 %) in short reaction time (4-18 min), simple work-up, and column chromatographic free synthesis are the remarkable features of this new protocol. The applicability of [Et3NH][HSO4] ionic-liquid as a green and inexpensive catalyst with good recyclability and compatibility with a broad range of functional group having heteroatom, electron-withdrawing, and electron-releasing groups manifested the sustainability, eco-friendliness, and efficiency of the present methodology. Moreover, the antioxidant studies of the synthesized compounds using DPPH and ABTS assays were appealing and several synthesized compounds showed significant antioxidant activity.

Novel Biologically Active N-Substituted Benzimidazole Derived Schiff Bases: Design, Synthesis, and Biological Evaluation

Herein, we present the design and synthesis of novel N-substituted benzimidazole-derived Schiff bases, and the evaluation of their antiviral, antibacterial, and antiproliferative activity. The impact on the biological activity of substituents placed at the N atom of the benzimidazole nuclei and the type of substituents attached at the phenyl ring were examined. All of the synthesized Schiff bases were evaluated in vitro for their antiviral activity against different viruses, antibacterial activity against a panel of bacterial strains, and antiproliferative activity on several human cancer cell lines, thus enabling the study of the structure-activity relationships. Some mild antiviral effects were noted, although at higher concentrations in comparison with the included reference drugs. Additionally, some derivatives showed a moderate antibacterial activity, with precursor 23 being broadly active against most of the tested bacterial strains. Lastly, Schiff base 40, a 4-N,N-diethylamino-2-hydroxy-substituted derivative bearing a phenyl ring at the N atom on the benzimidazole nuclei, displayed a strong antiproliferative activity against several cancer cell lines (IC₅₀ 1.1-4.4 μM). The strongest antitumoral effect was observed towards acute myeloid leukemia (HL-60).

DNA-binding, cleavage, antibacterial and in vitro anticancer activity of copper(II) mixed ligand complexes of 2-(((6-chloro-1H-benzo[d]imidazol-2-yl)methyl)amino)aceticacid and polypyridyl ligands

A tridentate ligand(A), 2-(((6-chloro-1H-benzo[d]imidazol-2-yl)methyl)amino) aceticacid (Cl-BIGH) was synthesised by the Phillips condensation of 4-chlorobenzene-1,2-diamine and iminodiaceticacid in 1:2 molar ratio. Its Cu(II) mixed ligand complexes[Cu(II)-A-L] were obtained by involving other co-ligands(L): 2,2΄-bipyridine(L₁), 4,4΄-dimethyl-2,2΄-bipyridyl(L₂), 5,5΄-dimethyl-2,2΄-bipyridyl(L₃) and 1,10 phenanthroline(L₄). The complexes were characterized by elemental analysis, thermal analysis, molar conductance, magnetic moment measurements, X-ray diffraction, FTIR, UV-Visible, ESR spectroscopy, mass spectrometry and cyclic voltammetry. From the spectral and analytical data, the ternary complexes [Cu(Cl-BIGH)(L_1-4)]ClO₄ were found to form in 1:1:1(Cu(II): Cl-BIGH: L) molar ratio. The geometry of the mixed-ligand complexes were found to be 5-coordinated square pyramidal or trigonal bipyramidal with polycrystalline natures. The DNA binding and cleaving abilities, antibacterial and the in vitro cytotoxicity of the complexes were explored. The molecular docking was used to predict the efficiency of binding of the metal complexes with COX- 2.Communicated by Ramaswamy H. Sarma.

Synthetic Approach to Potential Anticancer Benzimidazole Derivatives- A Review

Cancer is one of the deadliest diseases in many developed and developing countries. Continuous efforts are required for designing better therapeutic agents for the treatment of cancer with more efficacy, selectivity, and less toxicity. The fused heterocyclic ring system has been identified by several researchers as a privileged structure that can be used as a basis for drug discovery in medicinal chemistry. The hetero-aromatic bicyclic ring system acts as a pharmacophore in a wide range of drugs with therapeutic potential. According to studies in the literature, variously substituted benzimidazoles have distinct pharmacological profiles with multi-targeting ability, making them an important anchor for the production of novel therapeutic agents against complex cancers including breast cancer, skin cancer, and blood cancer. In this presented article we are discussed various synthetic methods for the synthesis of anticancer benzimidazoles and their derivatives in different solvent conditions, substrates, and various catalysts mainly those which are eco-friendly, and economical, which shows the anticancer activity. We also focused on various derivatives are under clinical trials containing Benzimidazole moiety.

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.

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.

Importance of Fluorine in Benzazole Compounds

Fluorine-containing heterocycles continue to receive considerable attention due to their unique properties. In medicinal chemistry, the incorporation of fluorine in small molecules imparts a significant enhancement their biological activities compared to non-fluorinated molecules. In this short review, we will highlight the importance of incorporating fluorine as a basic appendage in benzothiazole and benzimidazole skeletons. The chemistry and pharmacological activities of heterocycles containing fluorine during the past years are compiled and discussed.

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.

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

In order to explore and develop new anticancer agents, three series of 2-phenylbenzimidazoles, 15-46, were condensed under simple and mild conditions using sodium metabisulfite as an oxidation agent and another series, 47-55, were obtained via a reduction reaction using sodium borohydride. All the compounds synthesized were evaluated for their in vitro anticancer activities against three human cancer cell lines. The novel compound 38 was found to be the most potent multi cancer inhibitor against A549, MDA-MB-231, and PC3 cell lines (IC50 values 4.47, 4.68 and 5.50 μg mL-1, respectively). In addition, compound 40 exhibited the best IC50 value of 3.55 μg mL-1 against the MDA-MB-231 cell line. The results demonstrated that introducing a new substituent to compounds 37-55 could improve their antiproliferative activities.

A Green Approach for Organic Transformations Using Microwave Reactor

Microwave-assisted organic transformation (MAOR) is presently gaining wide popularity in the field of organic synthesis. The conventional heating technique is gradually being removed from the laboratory and a novel microwave heating technique established to be used in both academia and industry. As compared to the classical organic methodology, the green technology tools have several advantages like dramatically reduced reaction times, improved yields, site selectivity, and the increased product purities with simplification of work-up procedures. In the current study, we have briefly described the overview of recent developments and applications of microwave irradiation in organic transformation with schematic compiling of the organic reactions, bioactive heterocyclic compounds, and so on. This review also presents a critical analysis of the various advantages of microwave irradiation in organic synthesis/transformation compared to the classical or conventional heating. So, we believe that our current study of the green microwave heating technique will be highly beneficial for the researchers from both academia and industry in their near future.

Benzimidazole Schiff base derivatives: synthesis, characterization and antimicrobial activity

A series of Schiff bases (3.a–f) bearing benzimidazole moiety was successfully synthesized in ethanol by refluxing Oct-2-ynoic acid (1,3-dihydrobenzimidazole-2-ylidene)amide with substituted amines. Fourier transform infrared (FTIR), ultra violet light (UV–VIS), elemental analysis, proton (¹H) and carbon (¹³C) nuclear magnetic resonance spectroscopy were used to characterize the newly synthesized Schiff bases. Micro dilution method was used to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the Schiff bases, against 14 human pathogenic bacteria (8 Gram negative and 6 Gram positive) and against 7 fungal strains (5 Aspergillus and 2 Fusarium) representatives. Antimalarial activity against Plasmodium falciparum and antitrypanosomal property against Trypanosoma brucei was studied in vitro at a single dose concentration of the Schiff bases. Cytotoxicity of the Schiff bases was assessed against human cervix adenocarcinoma (HeLa) cells. Results obtained show that the newly synthesized Schiff bases are very potent antimicrobial agents. Gram negative bacteria Klebsiella pneumonia and Escherichia coli were more affected on exposure to Compounds 3.c–f (MIC 7.8 µg/mL) which in turn exhibited more antibacterial potency than nalidixic acid reference drug that displayed MICs between 64 and 512 µg/mL against K. pneumonia and E. coli respectively. The test compounds also demonstrated high cytotoxic effect against Aspergillus flavus and Aspergillus carbonarius as they displayed MFC 7.8 and 15.6 µg/mL. Compound 3.c exhibited the highest fungicidal property from this series with MFC alternating between 7.8 and 15.6 µg/mL against the investigated strains. The malarial activity revealed Compounds 3.c and 3.d as the more potent antiplasmodial compounds in this group exhibiting 95% and 85% growth inhibition respectively. The IC₅₀ of Compounds 3.c and 3.d were determined and found to be IC₅₀ 26.96 and 28.31 µg/mL respectively. Compound 3.a was the most cytotoxic agent against HeLa cells in this group with 48% cell growth inhibition. Compounds 3.c, 3.d and 3.f were biocompatible with HeLa cells and displayed low toxicity. With a very low cytotoxic effect against HeLa, compound 3.c stands out to be a very good antiparasitic agent and consideration to further evaluate the candidate drug against others cell lines is necessary.

Hydrothermal liquefaction of Malaysia's algal biomass for high-quality bio-oil production

Currently, fossil materials form the majority of our energy and chemical source. Many global concerns force us to rethink about our current dependence on the fossil energy. Limiting the use of these energy sources is a key priority for most countries that pledge to reduce greenhouse gas emissions. The application of biomass, as substitute fossil resources for producing biofuels, plastics and chemicals, is a widely accepted strategy for sustainable development. Aquatic plants including algae possess competitive advantages as biomass resources compared to the terrestrial plants in this current global situation. Bio-oil production from algal biomass is technically and economically viable, cost competitive, requires no capacious lands and minimal water use and reduces atmospheric carbon dioxide. The aim of this paper is to review the potential of converting algal biomass, as an aquatic plant, into high-quality crude bio-oil through applicable processes in Malaysia. In particular, bio-based materials and fuels from algal biomass are considered as one of the reliable alternatives for clean energy. Currently, pyrolysis and hydrothermal liquefaction (HTL) are two foremost processes for bio-oil production from biomass. HTL can directly convert high-moisture algal biomass into bio-oil, whereas pyrolysis requires feedstock drying to reduce the energy consumption during the process. Microwave-assisted HTL, which can be conducted in aqueous environment, is suitable for aquatic plants and wet biomass such as algae.

Molecular keypad controlled circuit for Ce(iii) and NO3− ions recognition by μw synthesized silicon-embedded organic luminescent sensor

This report demonstrates the mimicking of an electronic circuit diagram towards Ce(iii) ion sensing response supported by molecular keypads. The probe naphthyl based triazole linked silatrane (NTS) was efficiently synthesized using a series of microwave mediated reactions. The luminescent sensor NTS was explored for the ion sensing response towards Ce(iii) ions using DMSO and DMSO : H₂O 4 : 1 (v/v) as solvent media, respectively. The role of water in Ce(iii) ion sensing was detected as ‘turn-off’ response that contradicts the ‘turn-on’ with DMSO. Further, the sensing of NO₃⁻ ions by NTS–Ce(iii) ensemble was associated with blue shift on absorption maxima. These mimicking response studies were sketched as circuit diagrams assisted by molecular keypad behaviour as IMPLICATION output logic gate.

This report demonstrates the mimicking of an electronic circuit diagram towards Ce(iii) ion sensing response supported by molecular keypads.

Imidazoles as potential anticancer agents

Cancer is a black spot on the face of humanity in this era of science and technology. Presently, several classes of anticancer drugs are available in the market, but issues such as toxicity, low efficacy and solubility have decreased the overall therapeutic indices. Thus, the search for new promising anticancer agents continues, and the battle against cancer is far from over. Imidazole is an aromatic diazole and alkaloid with anticancer properties. There is considerable interest among scientists in developing imidazoles as safe alternatives to anticancer chemotherapy. The present article describes the structural, chemical, and biological features of imidazoles. Several classes of imidazoles as anticancer agents based on their mode of action have been critically discussed. A careful observation has been made into pharmacologically active imidazoles with better or equal therapeutic effects compared to well-known imidazole-based anticancer drugs, which are available on the market. A brief discussion of the toxicities of imidazoles has been made. Finally, the current challenges and future perspectives of imidazole based anticancer drug development are conferred.

Recent developments on ultrasound-assisted one-pot multicomponent synthesis of biologically relevant heterocycles

Heterocycles are the backbone of organic compounds. Specially, N- &O-containing heterocycles represent privileged structural subunits well distributed in naturally occurring compounds with immense biological activities. Multicomponent reactions (MCRs) are becoming valuable tool for synthesizing structurally diverse molecular entities. On the other hand, the last decade has seen a tremendous outburst in modifying chemical processes to make them sustainable for the betterment of our environment. The application of ultrasound in organic synthesis is fulfilling some of the goals of 'green and sustainable chemistry' as it has some advantages over the traditional thermal methods in terms of reaction rates, yields, purity of the products, product selectivity, etc. Therefore the synthesis of biologically relevant heterocycles using one-pot multi-component technique coupled with the application of ultrasound is one of the thrusting areas in the 21st Century among the organic chemists. The present review deals with the "up to date" developments on ultrasound assisted one-pot multi-component synthesis of biologically relevant heterocycles reported so far.

Recent Developments on Ultrasound-Assisted Synthesis of Bioactive N-Heterocycles at Ambient Temperature

N-Heterocycles represent privileged structural subunits well distributed in naturally occurring compounds with immense biological activities. The last decade has seen a tremendous practice to carry out reactions at ambient temperature avoiding harsh reaction conditions. By applying ultrasonic radiation in organic synthesis we can make synthetic protocols more sustainable and can carry out reactions at room temperature avoiding the traditional thermal harsh reaction conditions. Therefore the synthesis of biologically relevant N-heterocycles at room temperature under the influence of ultrasonic irradiation is one of the advancing areas in the 21st century among organic chemists. The present review summarises the latest developments on ultrasound-assisted synthesis of biologically relevant N-heterocycles at ambient temperature.

A Novel Mechanistic Study on Ultrasound-Assisted, One-Pot Synthesis of Functionalized Benzimidazo[2,1-b]quinazolin-1(1H)-ones

Ultrasound-assisted synthesis of benzimidazo[2,1-b]quinazolin-1(1H)-ones was achieved via piperidine-catalyzed three-component reaction of 2-aminobenzimidazoles, an aromatic aldehyde, and 1,3-dione in aqueous isopropanol. This mechanism was first suspected following our identification of unusual reaction intermediates in a one-pot reaction. An unprecedented coupling reaction, it involved a nucleophilic attack by 2-aminobenzimidazole on in situ generated Michael adduct, followed by electrocyclic ring formation reaction. In contrast to the commonly accepted mechanism, that the direct reaction of 2-amino benzimidazole with a Knoevenagel adduct cannot deliver target compounds.

Diversity oriented synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approach: a critical review

Because of the wide ranging bioactivities associated with the benzimidazole nucleus, this review highlights the advances made in the synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approaches.

Synthesis, biological evaluation and molecular modeling of 1H-benzo[d]imidazole derivatives as novel anti-tubulin polymerization agents

A series of novel compounds (8a–21b) were designed and synthesized based on 2-phenyl-1H-benzo[d]imidazole. Compound 18b showed the most potent in vitro growth inhibitory activity and significant tubulin polymerization inhibitory activity.

A simple and efficient fluorophoric probe for dual sensing of Fe3+and F−: application to bioimaging in native cellular iron pools and live cells

A quinoline functionalized fluorophore exhibited high selectivity towards Fe³⁺ions and the ligand–metal complex showed excellent selectivity towards F⁻ions.

Experimental and DFT studies on the vibrational and electronic spectra and NBO analysis of 2-amino-3-((E)-(9-p-tolyl-9H-carbazol-3-yl) methyleneamino) maleonitrile

2-Amino-3-((E)-(9-p-tolyl-9H-carbazol-3-yl) methyleneamino) maleonitrile (ACMM) was synthesized and characterized by X-ray diffraction, FT-IR, FT-Raman and UV-Vis spectra. The X-ray diffraction study showed that ACMM has a Z-configuration, due to the intramolecular C18H18A⋯N2, N3H3A⋯N2 and C20H20A⋯N4 hydrogen bonds and intermolecular C10H10A⋯N4, N3H3B⋯N9 (2-x, 2-y, 2-z) and N3H8C⋯N4 (2-x, 1-y, 2-z) hydrogen bonds. The benzene ring including methyl is twisted from the mean plane of the carbazole group by 59.7(3)°. Vibrational spectra and electronic spectra measurements were made for the compound. Optimized geometrical structure and harmonic vibrational frequencies were computed with DFT (B3-based B3P86, B3LYP, B3PW91 and B-based BP86, BLYP, BPW91) methods and ab initio RHF method using 6-311++G(d, p) basis set. Assignments of the observed spectra were proposed. The equilibrium geometries computed by all of the methods were compared with X-ray diffraction results. The absorption spectra of the title compound were computed both in gas phase and in DMF solution using TD-B3LYP/6-311++G(d, p) and PCM-B3LYP/6-311++G(d, p) approaches, respectively. The calculated results provide a good description of positions of the bands maxima in the observed electronic spectrum. Temperature dependence of thermodynamic parameters in the range of 100-1000K were determined. The bond orbital occupancies, contribution from parent natural bond orbital (NBO), the natural atomic hybrids was calculated and discussed.