Synthesis and DNA binding studies of novel heterocyclic substituted quinoline schiff bases: a potent antimicrobial agent

Quinoline Hydrazide/Hydrazone Derivatives: Recent Insights on Antibacterial Activity and Mechanism of Action

Antibiotics are becoming gradually ineffective due to drug resistance, leading to greater difficulty in the treatment of infectious diseases. Therefore, the development of new chemical entities with different mechanisms of action is essential in the fight against resistant microorganisms. Various studies have shown that quinoline hydrazide/hydrazone derivatives possess several biological activities, such as antimalarial, antitubercular, anticancer, anti-inflammatory, and antimicrobial. Among these activities, the antibacterial activity of quinoline hydrazide/hydrazone derivatives is noteworthy. The synthetic flexibility of the quinoline ring has led to the development of a wide range of structurally diverse quinoline hydrazide/hydrazone derivatives, which can act at various bacterial targets such as DNA gyrase, glucosamine-6-phosphate synthase, enoyl ACP reductase, and 3-ketoacyl ACP reductase. This review emphasizes the antibacterial potential of various reported quinoline hydrazide/hydrazone derivatives based on substitution in the quinoline ring. The antibacterial activity of various metal-quinoline hydrazide/hydrazone complexes is also discussed. The aim of this review is to assemble and scrutinize the latest reports in this promising area of drug development.

DNA Cleavage Properties, Antimicrobial and Cytotoxic Activity and 4D-QSAR Analysis of Some Pyrazole Derivatives

Background:

An extensive study of 19 pyrazole derivatives were carried out based on the evaluation of DNA cleavage properties, antimicrobial and cytotoxic activities and 4D-QSAR analysis including pharmacophore modelling and bioactivity prediction by the Electron Conformational-Genetic Algorithm (EC-GA) method.

Methods:

The pyrazole derivatives were tested for their antimicrobial activity against certain human pathogenic organisms using the agar diffusion procedure. Binding of compounds with DNA was studied by gel electrophoresis using plasmid pBR322 DNA. The compounds were investigated for their properties as cytotoxic agents by brine shrimp lethality bioassay. To identify the pharmacophoric elements and find out the most important molecular properties which govern cytotoxic activity, multiple conformations of the compounds were used.

Results:

The urea derivatives of pyrazole had higher antibacterial activities against Gram-negative bacteria than against Gram-positive bacteria. Many of the compounds were found to cleave plasmid pBR322 DNA from the supercoiled form to the nicked circular. The cytotoxicity values of the compounds ranged from 13.87 to 84.1 µg/mL. The generated QSAR model was evaluated through the use of the Leave-One-Out Cross Validation (LOO-CV) method. A statistically significant and considerably predictive QSAR model was obtained with 4- descriptors resulting in R2 training =0.8223, R2 test =0.9346, q2=0.6201, q2 ext1=0.8672, q2 ext2= 0.8662 and q2 ext3=0.9511.

Discussion:

The generated model demonstrates that geometrical parameters are more correlated with cytotoxic activity. The resulting EC-GA model would provide benefits to design novel bioactive pyrazole derivatives which are more potent and have less side effects.

Conclusion:

It is believed that the generated QSAR model gives insight into developing new more potent pyrazole derivative drugs.

Design, synthesis, in vitro anticancer, antioxidant and antibacterial activity; DNA/BSA binding, photoleavage and docking studies of Cu(II) ternary metal complexes

Three mononuclear, mixed ligand ternary Cu(II) complexes of 3-((Z)-1-(2-hydroxyphenylimino)ethyl)-4-hydroxy-6-methyl-2H-pyran-2-one (HEHMP) viz; [Cu-(Phen) (HEHMP)] (1a), [Cu-(Bpy)(HEHMP)] (1 b) and [Cu-Bpy(NCS)(HEHMP)] (1c) were synthesized and characterized by data obtained from various spectral techniques. The binding affinities of these complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein were explored by absorption and fluorescence quenching titrations. The results indicated strong affinity of the title compounds to bind with both CT-DNA and BSA. The antioxidant properties of the synthesized compounds evaluated by free-radical scavenging method using spectrophotometric technique indicated their affirmative potential activity. Gel electrophoresis experiments revealed the efficacy of metal complexes in resulting the cleavage of pBR322 supercoiled DNA. In vitro cytotoxicity studies of these complexes evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against HeLa and MCF-7 cancer cell lines indicated relatively high effectiveness of the complex 1c. Confocal microscopy signified the potential of the complexes to induce apoptosis in HeLa cell lines. In addition, the antibacterial activity of the compounds carried out by disc diffusion method revealed significantly enhanced antibacterial activity in Cu (II) ternary complexes compared to the activity of ligands in unbound form signifying the implicit role of metal ion in inducing lipophilic character.

New Quinolylnitrones for Stroke Therapy: Antioxidant and Neuroprotective ( Z)- N- tert-Butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine Oxide as a New Lead-Compound for Ischemic Stroke Treatment

We describe herein the synthesis and neuroprotective capacity of an array of 31 compounds comprising quinolyloximes, quinolylhydrazones, quinolylimines, QNs, and related heterocyclic azolylnitrones. Neuronal cultures subjected to oxygen-glucose deprivation (OGD), as experimental model for ischemic conditions, were treated with our molecules at the onset of recovery period after OGD and showed that most of these QNs, but not the azo molecules, improved neuronal viability 24 h after recovery. Especially, QN ( Z)- N-tert-butyl-1-(2-chloro-6-methoxyquinolin-3-yl)methanimine oxide (23) was shown as a very potent neuroprotective agent. Antioxidant analysis based on the ability of QN 23 to trap different types of toxic radical oxygenated species supported and confirmed its strong neuroprotective capacity. Finally, QN 23 showed also neuroprotection induction in two in vivo models of cerebral ischemia, decreasing neuronal death and reducing infarct size, allowing us to conclude that QN 23 can be considered as new lead-compound for ischemic stroke treatment.

Macrocyclic complexes: synthesis, characterization, antitumor and DNA binding studies

The present paper deals with the synthesis of novel macrocyclic complexes of the type [MLX]X, where [(M = Co(II) (1), and Ni(II) (2) X = (Cl₂)]. The complexes are synthesized by the reaction of ligand(L)diquinolineno[1,3,7,9]tetraazacyclododecine-7,15-ethane(14H,16H)-benzene with the corresponding metal salts. The synthesized complexes are thoroughly characterized by elemental analysis, FT-IR, ¹H-NMR, Mass and electronic spectra. The complexes (1) and (2) were evaluated for in vitro cytotoxicity against human breast adenocarcinoma cell (MCF-7). MTT cytotoxicity studies shows both the complexes are most effective. The binding properties of these complexes with calf thymus-DNA were studied by absorption, emission spectra, viscosity measurements, and thermal denaturation studies. On binding to CT-DNA, the absorption spectrum undergoes bathochromic and hypochromic shifts. The absorption spectral results indicate that the intrinsic binding constant (K_b) are 4.8 × 10⁵ M^-1 for (1) and 3.9 × 10⁵ M^-1 for (2) respectively, suggesting that complex (1) binds more strongly to CT-DNA than complex (2). The viscosity measurement results revealed the viscosity of sonicated rod like DNA fragments increased when the complex was added to the solution of CT-DNA. The synthesized ligand and its metal complexes are screened for antibacterial and antifungal activities.

Synthesis and Biological Evaluation of New Hydrazone Derivatives of Quinoline and Their Cu(II) and Zn(II) Complexes against Mycobacterium tuberculosis

A new series of quinoline hydrazone derivatives and their metal complexes have been synthesized and their biological properties have been evaluated against Mycobacterium tuberculosis (H37 RV strain). Most of the newly synthesized compounds displayed 100% inhibitory activity at a concentration of 6.25–25 μg/mL, against Mycobacterium tuberculosis. Fluorescence properties of all the synthesized compounds have been studied.

Combined experimental and theoretical studies on the X-ray crystal structure, FT-IR, 1H NMR, 13C NMR, UV-Vis spectra, NLO behavior and antimicrobial activity of 2-hydroxyacetophenone benzoylhydrazone

A Schiff base ligand, 2-hydroxyacetophenone benzoylhydrazone (HL) was synthesized and fully characterized with FT-IR, elemental analyses, UV-Vis, (1)H NMR and (13)C NMR spectra. DFT calculations using B3LYP/6-31+G(d,p) and PW91/DZP are performed to optimize the molecular geometry. Optimized structures are used to calculate FT-IR, UV-Vis, (1)H NMR and (13)C NMR spectra of the compound. Also the energies of the frontier molecular orbitals (FMOs) have been determined. The results obtained from the optimization and spectral analyses are in good agreement with the experimental data. To investigate non-linear optical properties, the electric dipole moment (μ), polarizability (α) and molecular first hyperpolarizability (β) were computed. The linear polarizabilities and first hyperpolarizabilities of the studied molecule indicate that the compound can be a good candidate of nonlinear optical materials. In addition, the minimal inhibitory concentration (MIC) of this compound against Staphylococcus aureus, and Candida albicans was determined.

Synthesis, antitumor, and DNA binding behavior of novel 4-(2-hydroxyquinolin-3-yl)-6-phenyl-5, 6 dihydropyrimidin derivatives in aqueous medium

This article deals with the synthesis of 4-(2-hydroxyquinolin-3-yl)-6-phenyl-5,6-dihydropyrimidin derivatives (2a-f), on condensation with various aromatic aldehydes and ketones in aqueous ethanolic NaOH solution yielding the corresponding chalcones (3). These chalcones were further reacted with thiourea/urea in the presence of a base, which led to the formation of the titled derivatives (2a-f). The newly synthesized heterocyles were characterized by elemental analysis, FTIR, (1)HNMR, and electronic and mass spectral data. The compounds (2a and 2b) were evaluated for in vitro cyctotoxicity against human breast adenocarcinoma cell (MCF-7). In MTT cytotoxicity studies, both quinolinde derivatives were found most effective. The binding interaction behavior of the compound (2a) and (2d) with calf thymus-DNA (CT-DNA) was studied by electronic spectra, viscosity measurements, and thermal denaturation studies. On binding to CT-DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. The binding constant (K(b)) observed 4.3 x 10(5) M(-1) for (2a), and 3.8 x 10(5) M(-1) for (2d) suggested that compound (2a) binds more strongly with base pairs than (2d).