Synthesis, characterization and antimicrobial activity of 1,3,4-oxadiazole bearing 1H-benzimidazole derivatives

Synthesis and Anti-Inflammatory Activity Evaluation of Some Benzimidazole Derivatives

Hyper-inflammation aggravates the symptoms of both communicable and non-communicable diseases. Therefore, anti-inflammatory compounds may have wide therapeutic application. Benzimidazole is a privileged scaffold and its success in drug development is evident from the long list of benzimidazole-based drugs with wide range of applications. This study was undertaken to develop new small molecules with anti-inflammatory properties. Compounds MBPHYD, MBNHYD and MBHYDX were synthesised, purified, characterised and found to be non-toxic both in vitro (in 100 μMconcentration for 24 h vs. 3000 Vero cells/well) and in vivo (at a dose of 100 mg/kg in female Wistar rats with animals observed for 48 h for any mortality). Compounds MBPHYD and MBNHYD were found to possess significant anti-inflammatory properties. Further, in silico analysis suggested their compliance with drug-likeness. While no toxicity was predicted, both compounds were suggested to have good oral bioavailability. Thus, results of this study may encourage further investigation to establish new anti-inflammatory benzimidazoles for application against various disease conditions.

New benzimidazole based hybrids: Synthesis, molecular modeling study and anticancer evaluation as TopoII inhibitors

Three series of new benzimidazole hybrids were designed and synthesized as promising human TopoII inhibitors. They were characterized by different spectroscopic techniques (¹H, ¹³C NMR, ESI-MS and IR). All hybrids (6-23) were screened for their in vitro antiproliferative activity against five human cancer cell lines namely; HepG-2, MCF-7, PC-3, HCT-116 and Hela. Compound 21 showed the most potent anticancer activity against all cancer cell lines, with IC₅₀ range of 2.82 to 12.59 µM, while proving safe towards normal cells WI-38 (IC₅₀ = 31.89 µM) compared to the reference drug doxorubicin (IC₅₀ = 6.72 µM). The most active candidates 13, 20, 21, 22 and 23 were further assessed for their human TopoII inhibition. The best of which, compounds 13 and 20 showed IC₅₀ of 6.72 and 8.18 µM respectively compared to staurosporine (IC₅₀ = 4.64 µM). Further mechanistic studies for compound 13 showed cell cycle arrest at S-phase by 51.29 % and a significant increase in the total apoptosis by 62.5 folds. Furthermore, apoptosis study proved that it induced apoptosis by decreasing both IAP and Bcl-2, activating caspases 3, 8 and 9, and increasing accumulation of ROS in HepG-2 cells. Besides, it decreased transcription factors' binding activity to DNA. Comparative molecular docking study was performed between the most potent TopoII inhibitors 13 and 20, and the least potent one 23 to relate the binding pattern with TopoII catalytic active site to the biological activity, where all results came in agreement with the biological results. Additional molecular modeling studies including surface mapping and contact preferences were performed to emphasize the importance of hydrophobicity. Physicochemical calculations were assessed where compounds 13 and 20 represented very promising orally active drug candidates.

Synthesis, in silico studies and antibacterial activity of some novel 2-substituted benzimidazole derivatives

Background

The o-phenylenediamine is a versatile starting material for several compounds. Synthesized o-phenylenediamine and amino acids (glycine, alanine, aspartic acid, and l-proline) undergo condensation via Phillips reaction. The synthesized compound showed the promising antibacterial activity of Bacillus subtilis and Pseudomonas aeruginosa at the concentration of 100, 50, 25, 12.5, 6.25, 3.12, 1.6, 0.8, 0.4, and 0.2 μg/ml. Ciprofloxacin was used as standard drug. Synthesis of benzimidazole derivatives was carried out and purified by recrystallization process using ethanol. Substituted derivatives were characterized by melting point, TLC and spectroscopic methods include FT-IR and 1H-NMR.

Results

In silico studies were adopted for synthetic derivatives by Molinspiration, ChemDraw, and online software tool. Minimum inhibitory concentration (MIC) values of B. subtilis and P. aeruginosa were reported, and benzimidazole ligands and Molinspiration scores were generated and listed.

Conclusion

The more negative values indicate a higher binding affinity. The generated ligand observations can be visualized. Physical constants of synthesized derivates such as solubility and melting point were determined. Bioactivity scores were noted for different derivatives and predicted percentage absorption in the gut. The antibacterial activity was performed using the MIC method (aerobic).

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.

Synthesis of pyrazole acrylic acid based oxadiazole and amide derivatives as antimalarial and anticancer agents

Depravity of malaria in terms of morbidity and mortality in human beings makes it a major health issue in tropical and subtropical areas of the globe. Drug counterfeiting and non-adherence to the treatment regimen have significantly contributed to development and spread of multidrug resistance that has highlighted the need for development of novel and more efficient antimalarial drugs. Complexity associated with cancer disease and prevalence of diversified cell populations vindicates highly specific treatment options for treatment of cancer. Resistance to these anticancer agents has posed a great hindrance in successful treatment of cancer. Pondering this ongoing situation, it was speculated to develop novel compounds targeting malaria and cancer. Moving on the same aisle, we synthesized pyrazole acrylic acid based oxadiazole and amide derivatives using multi-step reaction pathways (6a-x; 6a'-h'). Schizont maturation inhibition assay was employed to determine antimalarial potential. Compound 6v emerged as the most potent antimalarial agent targeting falcipain-2 enzyme. Anticancer activity was done using sulforhodamine B assay. Compounds 6b' and 6g' demonstrated promising results against all the tested cell lines. Further, Microscopic view clearly indicated formation of apoptotic bodies, chromatin condensation, shrinkage of cells and bleb formation. Validation of the results was achieved using molecular docking studies. From the obtained results, it was observed that cyclization (oxadiazole) favored antimalarial activity while non-cyclized compounds (amides) emerged as better anticancer agents.

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.

Synthesis, characterization, and in vitro anticancer evaluation of novel 2,5-disubstituted 1,3,4-oxadiazole analogue

In this series, we have synthesised a new 2,5-disubstituted 1,3,4-oxadiazole in search of potential therapeutics for cancer. The anticancer activities were evaluated on a panel of 60 cell lines by the National Cancer Institute according to its own screening protocol. Out of the 24 compounds, 11 were selected and evaluated via single high dose (10⁻⁵ M). In the next phase, two compounds have been selected for five-dose assay. The compounds 3-(5-benzyl-1,3,4-oxadiazol-2-yl)quinolin-2(1H)-one 18 (NSC-776965) and 3-[5-(2-phenoxymethyl-benzoimidazol-1-ylmethyl)-[1,3,4]oxadiazol-2-yl]-2-p-tolyloxy-quinoline 27 (NSC-776971) showed mean growth percentage of 66.23 and 46.61, respectively, in one-dose assay and their GI₅₀ values ranging between 1.41–15.8 μM and 0.40–14.9 μM, respectively, in 5-dose assay.