Synthesis and antimicrobial activity of some novel 2,5- and/or 6-substituted benzoxazole and benzimidazole derivatives

Investigation of Novel Quinoline-Thiazole Derivatives as Antimicrobial Agents: In Vitro and In Silico Approaches

Infectious diseases are a major concern around the world. Today, it is an urgent need for new chemotherapeutics for infectious diseases. Because of that, our group designed, synthesized, and analyzed 14 new quinoline derivatives endowed with the pharmacophore moiety of fluoroquinolones primarily for their antimicrobial effects. Their cytotoxicity effects were tested against six bacterial and four fungal strains and NIH/3T3 cell line. Additionally, their action mechanisms were evaluated against DNA gyrase and lanosterol 14α-demethylase (LMD). Furthermore, to eliminate the potential side effects, the active compounds were evaluated against the aromatase enzyme. The experimental enzymatic results were evaluated for active compounds' binding modes using molecular docking and molecular dynamics simulation studies. The results were utilized to clarify the structure-activity relationship (SAR). Finally, compound 4m was the most potent compound for its antifungal activity with low cytotoxicity against healthy cells and fewer possible side effects, while compounds 4j and 4l can be used alone for special patients who are suffering from fungal infections in addition to the primer disease.

Light-activated cytotoxicity of dicarbonyl Ru(II) complexes with a benzimidazole coligand towards breast cancer

Reaction between [RuCl2(CO)2]n and 1H-benzimidazol-2-ylmethyl-(N-phenyl)amine ligands (LR) functionalized with various electron-donating and electron-withdrawing substituents on the phenyl ring (R = H, 4-CH3, 4-Cl, 4-COOCH3, and 3-COOCH3) afforded the dark-stable photoactivatable carbon monoxide prodrugs of the general formula [RuCl2(CO)2LR]. Release of the CO molecules from the Ru(II) compounds was examined by monitoring the electronic and IR spectra upon illumination at 365 nm. A noticeable decrease in the intensities of the two characteristic ν(CO) modes for Ru(CO)II2 species, and the growth of two new bands for the mono-carbonyl species and free CO, were the main features of the photolysis profiles. The cytotoxicity of the complexes towards breast cancer (MCF-7) cells was assessed with and without illumination at 365 nm. All the complexes except that with a 4-COOCH3 group (IC50 = 45.08 ± 3.5 μM) are nontoxic under dark conditions. Upon illumination, all the compounds acquired cytotoxicity in the following order: H > 4-COOCH3 > 4-CH3 > 4-Cl > 3-COOCH3. Investigation of the cytotoxicity of the CO-depleted fragments showed that the light-induced cytotoxicity can be attributed to the liberated CO and CO-depleted metal fragments, including the liberated benzimidazole ligands.

Synthesis and reactivity of N-[3-amino-4-(benzoxazol-2-yl)pyrazol-5-yl]phenylamine

Pyrazolo[5,1- a]pyrimidines and pyrazolo[5,1-c][1,2,4]triazines containing benzooxazole moiety are synthesised from N-[3-amino-4-(benzoxazol-2-yl)pyrazol-5-yl]phenylamine or its diazonium chloride with the appropriate active methylene compounds. The newly synthesised compounds were elucidated by elemental analysis, spectral data and alternative synthetic route whenever possible.

The synthesis of benzimidazoles via a recycled palladium catalysed hydrogen transfer under mild conditions

An efficient synthesis of benzimidazoles was developed by virtue of a recycled palladium catalyzed hydrogen transfer.

Synthesis of substituted phenanthrene-9-benzimidazole conjugates: Cytotoxicity evaluation and apoptosis inducing studies

A series of new phenanthrene-9-benzimidazole conjugates has been synthesized by condensing phenanthrene aldehydes with various substituted o-phenylenediamines. The title compounds were evaluated for their in vitro cytotoxic potential against various human cancer cell lines like breast (BT-549), prostate (PC-3 and DU145), triple negative breast cancer (MDA-MB-453), and human colon cancer (HCT-116 and HCT-15) cells. Among the tested compounds, 10o displayed significant in vitro cytotoxic activity against PC-3 prostate cancer cells with an IC₅₀ value of 6.32 ± 0.09 μM. Further, the cell cycle analysis indicated that it blocks G2/M phase of the cell cycle in a dose dependent manner. In order to determine the effect of the compound 10o on cell viability; phase contrast microscopy, AO/EB staining, DAPI staining, and DCFDA staining studies were performed. In these studies, apoptotic features were clearly observed indicating that the compound inhibited cell proliferation by apoptosis. JC-1 staining and annexin binding assays indicated the extent of apoptosis in PC-3 cells. Further, relative viscosity measurements and molecular docking studies indicated that these compounds bind to DNA by intercalation.

A Novel Galectin-1 Inhibitor Discovered through One-Bead Two-Compound Library Potentiates the Antitumor Effects of Paclitaxel in vivo

Through the one-bead two-compound (OB2C) ultra-high-throughput screening method, we discovered a new small-molecule compound LLS2 that can kill a variety of cancer cells. Pull-down assay and LC/MS-MS indicated that galectin-1 is the target protein of LLS2. Galectin-1 is known to be involved in the regulation of proliferation, apoptosis, cell cycle, and angiogenesis. Binding of LLS2 to galectin-1 decreased membrane-associated H-Ras and K-Ras and contributed to the suppression of pErk pathway. Importantly, combination of LLS2 with paclitaxel (a very important clinical chemotherapeutic agent) was found to exhibit synergistic activity against several human cancer cell lines (ovarian cancer, pancreatic cancer, and breast cancer cells) in vitro Furthermore, in vivo therapeutic study indicated that combination treatment with paclitaxel and LLS2 significantly inhibits the growth of ovarian cancer xenografts in athymic mice. Our results presented here indicate that the OB2C combinatorial technology is a highly efficient drug screening platform, and LLS2 discovered through this method can be further optimized for anticancer drug development. Mol Cancer Ther; 16(7); 1212-23. ©2017 AACR.

Antitumor activities on HL-60 human leukemia cell line, molecular docking, and quantum-chemical calculations of some sulfonamide-benzoxazoles

We previously synthesized some novel benzoxazole derivatives-containing sulfonamide. In this study, the compounds were investigated for their antitumor activities against the HL-60 human leukemia cells, using the MTT assay. Moreover, quantum chemical calculations using the DFT methods were applied for understanding the difference in antitumor activity. Additionally, molecular docking into active site of the DNA Topo II enzyme was performed on 3QX3. PDB file in order to find out possible mechanism of antitumor effect. According to all obtained results showed that compounds 1b, 1c, and 1d could be potential drug candidates as new antitumor agents, and are promising for cancer therapy.

Synthesis and antimicrobial activity of novel benzoxazine sulfonamide derivatives

A new series of benzoxazine-6-sulfonamide derivatives were synthesized in excellent yields and the resulting compounds were evaluated for their antimicrobial activities. All the synthesized compounds were assessed for their antibacterial and antifungal activities. Among them 1a, 1b, 1c, 1e, 1h, 2c, 2d, 2e, 2g, 2h, 2i, 2j, 2k and 2l showed low inhibitory concentration (MIC of 31.25 and 62.5 μg/mL) against Gram-positive bacteria, Gram-negative bacteria and fungi, which are comparable to the inhibitory effect of standard drugs.

Octyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylate: complex sheets built from N-H···N, C-H···N and C-H···O hydrogen bonds

In the title compound, C29H35ClN4O2, the bond lengths provide evidence for aromatic delocalization in the pyrazole ring but bond fixation in the fused imidazole ring, and the octyl chain is folded, rather than adopting an all-trans chain-extended conformation. A combination of N-H···N, C-H···N and C-H···O hydrogen bonds links the molecules into sheets, in which the hydrogen bonds occupy the central layer with the tert-butyl and octyl groups arranged on either side, such that the closest contacts between adjacent sheets involve only the octyl groups. Comparisons are made with the supramolecular assembly in some simpler analogues.

Quantum mechanical and spectroscopic (FT-IR, FT-Raman, ¹H NMR and UV) investigations of 2-(phenoxymethyl)benzimidazole

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-(phenoxymethyl)benzimidazole have been investigated experimentally and theoretically using Gaussian09 software package. The energy and oscillator strength calculated by time dependent density functional theory results almost compliments with experimental findings. Gauge-including atomic orbital (1)H NMR chemical shifts calculations were carried out and compared with experimental data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Molecular Electrostatic Potential was performed by the DFT method and the infrared intensities and Raman activities have also been reported. Mulliken's net charges have been calculated and compared with the atomic natural charges. First hyperpolarizability is calculated in order to find its role in non-linear optics.

Synthesis and anticancer activity evaluation of N-[4-(2-methylthiazol-4-yl)phenyl]acetamide derivatives containing (benz)azole moiety

A new class of novel thiazole-(benz)azole derivatives was synthesized to investigate their anticancer activity. The structure of the compounds was confirmed by IR, (1)H-NMR, and MS spectral data and elemental analyses. Anticancer effect of the compounds was evaluated against A549 and C6 tumor cell lines. MTT, analysis of DNA synthesis, acridine orange/ethidium bromide staining method and analysis of caspase-3 activation assays were performed for anticancer activity investigations. Compounds 6f and 6g, which carry 5-chloro and 5-methylbenzimidazole groups showed significant anticancer activity. Potential of these compounds to direct tumor cells to apoptotic pathway, which is a precondition of anticancer action, was also observed.

Synthesis, Antibacterial and Antioxidant Evaluation of Novel 1-(5,7-Dichloro-1,3-benzoxazol-2-yl)-1H-pyrazolo[3,4-b]quinoline Derivatives

Some novel 1-(5,7-dichloro-1,3-benzoxazol-2-yl)-1H-pyrazolo[3,4-b]quinoline derivatives8(a–f) were synthesized by reacting 5,7-dichloro-2-hydrazino-1,3-benzoxazole4and substituted-2-chloro-3-quinoline carbaldehydes usingp-toluenesulfonic acid (PTSA) as a catalyst for the cyclisation. The target molecules have been characterized by IR,1H NMR,13C NMR, and mass spectral studies. The synthesized compounds were screened for biological activities, and some of the compounds have exhibited encouraging antibacterial and antioxidant activities. The compounds8aand8eshowed potent antibacterial activity, whereas the compounds8eand8fact as antioxidants.

The therapeutic journey of benzimidazoles: a review

Presence of benzimidazole nucleus in numerous categories of therapeutic agents such as antimicrobials, antivirals, antiparasites, anticancer, anti-inflammatory, antioxidants, proton pump inhibitors, antihypertensives, anticoagulants, immunomodulators, hormone modulators, CNS stimulants as well as depressants, lipid level modulators, antidiabetics, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substitutents around the benzimidazole nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, Angiotensin I (AT(1)) receptor antagonism and proton-pump inhibition is reviewed separately in literature. Even some very short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing benzimidazole nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of benzimidazole nucleus in medicinal chemistry research. In the present review, various derivatives of benzimidazole with different pharmacological activities are described on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole derived compounds for each activity. This discussion will further help in the development of novel benzimidazole compounds.

Molecular structures of 2-arylaminomethyl-1H-benzimidazole: spectral, electrochemical, DFT and biological studies

In the present work, structural studies on (1H-benzimidazol-2-ylmethyl)-N-(4-chloro-phenyl)-amine (L(1)) and (1H-benzimidazol-2-ylmethyl)-N-(4-iodo-phenyl)-amine (L(2)) have been done extensively by a variety of physico-chemical techniques. Optimized geometrical structures, harmonic vibrational frequencies, natural bonding orbital (NBO) analysis, and Frontier molecular orbitals (FMO) were obtained by DFT/B3LYP method. TD-DFT calculations help to assign the electronic transitions. The polarizable continuum model (PCM) fails to describe the experimental chemical shift associated with the NH protons as calculated by applying Gauge-invariant atomic orbital (GIAO) method, but a very good correlation between the theoretical and experimental values was achieved by taking into account the specific solute-solvent interactions. DFT calculations showed a good agreement between the theoretical and observed results. These compounds exhibited a high biological activity through the inhibition of the metabolic growth of the investigated bacteria.

An efficient synthesis of highly functionalized novel chromeno[4,3-b]pyrroles and indolizino[6,7-b]indoles as potent antimicrobial and antioxidant agents

A facile and efficient synthesis of novel chromeno[4,3-b]pyrroles has been accomplished by intramolecular 1,3-dipolar cycloaddition which on subsequent Pictet-Spengler cyclisation in presence of p-toluenesulfonic acid yielded indolizino[6,7-b]indoles. The synthesized chromenopyrroles and indolizinoindoles were evaluated for their antimicrobial and antioxidant activities. Compounds 7b, 7e, 7a and 7d exhibited respectively, good antibacterial and antifungal activities against tested pathogens when compared to reference control.

Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential antitumor agents

Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d]imidazole-5-carboxylates 11 were synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (S(N)Ar) and a solvent free approach as key steps for the formation of the desired products. Structure of intermediates and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI(50) range of 1.15-7.33 μM and 0.167-7.59 μM, respectively, and suitable LC(50) with values greater than 100 μM.

Design and synthesis of anti-MRSA benzimidazolylbenzene-sulfonamides. QSAR studies for prediction of antibacterial activity

A series of benzimidazolylbenzenesulfonamide compounds containing electron-releasing and electron-withdrawing substituents were synthesized and tested for their in vitro antibacterial activity. Two BZS compounds showed strong antibacterial activity against methicillin-resistant Staphylococcus aureus and Bacillus subtilis. Quantitative studies of their structure-activity relationship using a simple linear regression analysis were applied to explore the correlation between the biological activity and the charges on acidic hydrogen atoms in the synthesized compounds.

Synthesis, antimicrobial evaluation and QSAR studies of novel piperidin-4-yl-5-spiro-thiadiazoline derivatives

In an attempt to find a new class of antimicrobial agents, a series of new 1,3,4-thiadiazolines were synthesized from 2,6-diarylpiperidin-4-ones, via the corresponding 4'-phenylthiosemicarbazones. All the synthesized compounds (23-39) were virtually screened against bacterial (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi) and fungal strains (Candida albicans, Rhizopus sp, Aspergillus niger and Aspergillus flavus) by serial dilution method. QSAR study indicated that the increase in weakly polar component of solvent accessible surface area will favour antibacterial activity while increase in polarizability and decrease in ionisation potential and hydrogen bond donor will favour antifungal activity.

Synthesis and antimicrobial activity of novel fluorine containing 4-(substituted-2-hydroxybenzoyl)-1H-pyrazoles and pyrazolyl benzo[d]oxazoles

A series of fluorine containing 4-(substituted-2-hydroxybenzoyl) pyrazoles and pyrazolyl benzo[d]oxazoles were synthesized and evaluated for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis and antifungal activity against Candida albicans. The antibacterial activities were expressed as the minimum inhibitory concentration (MIC50) in microg/ml. The compounds 1-(3,4-difluorophenyl)-4-(5-fluoro-2-hydroxybenzoyl)-1H-pyrazole (4b), oxime derivatives such as 1-(3,4-difluorophenyl)-1H-pyrazol-4-yl)(2-hydroxy-4-methylphenyl)methanone oxime (5b) and (5-chloro-2-hydroxyphenyl)(1-(3,4-difluorophenyl)-1H-pyrazol-4-yl)methanone oxime (5e) exhibited promising activities against tested bacterial strains. Except compound 1-(3,4-difluorophenyl)-4-(2-hydroxybenzoyl)-1H-pyrazole (4d), none of the other compounds showed promising antifungal activity.