An overview on novel synthetic approaches and medicinal applications of benzimidazole compounds

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.

Synthesis and Photophysical Characterizations of Benzimidazole Functionalized BODIPY Dyes

Herein, a series of new BODIPY dyes substituted by 2-phenyl benzimidazole units at the meso (C8) position including methyl/ethyl, phenyl, or p-methoxyphenyl moieties at the distal and proximal positions of the BODIPY core have been successfully synthesized and their photophysical characteristics were analyzed. Experimentally investigating absorption and fluorescence profiles in the THF media was followed by density functional theory (DFT) calculations to clarify photophysical features. Theoretical analyses have revealed that upon excitation, both electrons and holes are confined solely within the BODIPY core. The energy levels of the frontier molecular orbitals converge depending on the presence of the phenyl and p-methoxyphenyl substituents. The orbital distributions of both electron and hole were in the -3 and -5 positions, which demonstrates a continuous conjugation with the BODIPY core at these sites. However, the electron density present on the phenyl rings located at the -1, -7, and -8 (meso) positions was found to be negligible. The benzimidazole-BODIPYs exhibited photodynamic activity (Φ∆) ranging from ~ 7% to ~ 11%, determined by a comparative method. Moreover, the compounds have shown to maintain their stability thermally in a non-reactive/inert environment up to temperatures surpassing 300 °C, exhibiting primarily a two-phase decomposition process. These compounds have the potential to function as antibacterial and anti-biofilm agents when used in concentrations ranging from 0.5 to 2.0 mg/mL. The results provide a basis for evaluating heterocyclic benzimidazole units on photophysical processes containing BODIPY chromophores.

Novel tetrahydropyrimidinyl-substituted benzimidazoles and benzothiazoles: synthesis, antibacterial activity, DNA interactions and ADME profiling

A series of tetrahydropyrimidinyl-substituted benzimidazoles attached to various aliphatic or aromatic residues via phenoxymethylene were synthesised to investigate their antibacterial activities against selected Gram-positive and Gram-negative bacteria. The influence of the type of substituent at the C-3 and C-4 positions of the phenoxymethylene linker on the antibacterial activity was observed, showing that the aromatic moiety improved the antibacterial potency. Of all the evaluated compounds, benzoyl-substituted benzimidazole derivative 15a was the most active compound, particularly against the Gram-negative pathogens E. coli (MIC = 1 μg mL^-1) and M. catarrhalis (MIC = 2 μg mL^-1). Compound 15a also exhibited the most promising antibacterial activity against sensitive and resistant strains of S. pyogenes (MIC = 2 μg mL^-1). Significant stabilization effects and positive induced CD bands strongly support the binding of the most biologically active benzimidazoles inside the minor grooves of AT-rich DNA, in line with docking studies. The predicted physico-chemical and ADME properties lie within drug-like space except for low membrane permeability, which needs further optimization. Our findings encourage further development of novel structurally related 5(6)-tetrahydropyrimidinyl substituted benzimidazoles in order to optimize their antibacterial effect against common respiratory pathogens.

Metagenomic-Metabolomic Mining of Kinema, a Naturally Fermented Soybean Food of the Eastern Himalayas

Kinema is a popular sticky fermented soybean food of the Eastern Himalayan regions of North East India, east Nepal, and south Bhutan. We hypothesized that some dominant bacteria in kinema may contribute to the formation of targeted and non-targeted metabolites for health benefits; hence, we studied the microbiome-metabolite mining of kinema. A total of 1,394,094,912 bp with an average of 464,698,304 ± 120,720,392 bp was generated from kinema metagenome, which resulted in the identification of 47 phyla, 331 families, 709 genera, and 1,560 species. Bacteria (97.78%) were the most abundant domain with the remaining domains of viruses, eukaryote, and archaea. Firmicutes (93.36%) was the most abundant phylum with 280 species of Bacillus, among which Bacillus subtilis was the most dominant species in kinema followed by B. glycinifermentans, B. cereus, B. licheniformis, B. thermoamylovorans, B. coagulans, B. circulans, B. paralicheniformis, and Brevibacillus borstelensis. Predictive metabolic pathways revealed the abundance of genes associated with metabolism (60.66%), resulting in 216 sub-pathways. A total of 361 metabolites were identified by metabolomic analysis (liquid chromatography-mass spectrophotometry, LC-MS). The presence of metabolites, such as chrysin, swainsonine, and 3-hydroxy-L-kynurenine (anticancer activity) and benzimidazole (antimicrobial, anticancer, and anti-HIV activities), and compounds with immunomodulatory effects in kinema supports its therapeutic potential. The correlation between the abundant species of Bacillus and primary and secondary metabolites was constructed with a bivariate result. This study proves that Bacillus spp. contribute to the formation of many targeted and untargeted metabolites in kinema for health-promoting benefits.

Rh(III)-Catalyzed Synthesis of Indazolo[2,3-a]quinolines: Vinylene Carbonate as C1 and C2 Building Blocks

A rhodium-catalyzed cyclization of azobenzenes and vinylene carbonate via C-H bond activation to construct indazolo[2,3-a]quinolines has been developed. This protocol offers an efficient method for synthesis of the titled products in good yields with broad functional group tolerance. In this reaction, three C-C bonds and C-N bond are formed in one pot, and vinylene carbonate (VC) acts as C1 and C2 synthons as well as "vinylene transfer" agent and acylation reagent in the construction of target-fused heterocycles. Moreover, the products exhibit favorable fluorescence properties, which indicate their potential application as fluorescent materials and biosensors.