Facilely accessible quinoline derivatives as potent antibacterial agents

Synergistic Augmentation of Beta-Lactams: Exploring Quinoline-Derived Amphipathic Small Molecules as Antimicrobial Potentiators against Methicillin-Resistant Staphylococcus aureus

The escalation of bacterial resistance against existing therapeutic antimicrobials has reached a critical peak, leading to the rapid emergence of multidrug-resistant strains. Stringent pathways in novel drug discovery hinder our progress in this survival race. A promising approach to combat emerging antibiotic resistance involves enhancing conventional ineffective antimicrobials using low-toxicity small molecule adjuvants. Recent research interest lies in weak membrane-perturbing agents with unique cyclic hydrophobic components, addressing a significant gap in antimicrobial drug exploration. Our study demonstrates that quinoline-based amphipathic small molecules, SG-B-52 and SG-B-22, significantly reduce MICs of selected beta-lactam antibiotics (ampicillin and amoxicillin) against lethal methicillin-resistant Staphylococcus aureus (MRSA). Mechanistically, membrane perturbation, depolarization, and ROS generation drive cellular lysis and death. These molecules display minimal in vitro and in vivo toxicity, showcased through hemolysis assays, cell cytotoxicity analysis, and studies on albino Wistar rats. SG-B-52 exhibits impressive biofilm-clearing abilities against MRSA biofilms, proposing a strategy to enhance beta-lactam antibiosis and encouraging the development of potent antimicrobial potentiators.

Investigating the Molecular Interactions of Quinoline Derivatives for Antibacterial Activity Against Bacillus subtilis: Computational Biology and In Vitro Study Interpretations

Bacterial infections are evolving and one of the chief problems is emergence and prevalence of antibacterial resistance. Moreover, certain strains of Bacillus subtilis have become resistant to several antibiotics. To counteract this menace, the present work aimed to comprehend the antibacterial activity of synthesized two quinoline derivatives against Bacillus subtilis. Toxicity predictions via Protox II, SwissADME and T.E.S.T (Toxicity Estimation Software Tool) revealed that these derivatives were non-toxic and had little to no adverse effects. Molecular docking studies carried out in Schrodinger with two quinoline derivatives (referred Q1 and Q2) docked against selected target proteins (PDB IDs: 2VAM and1FSE) of B. subtilis demonstrated ideal binding energies (2VAM-Q1: - 4.63 kcal/mol and 2VAM-Q2: - 4.46 kcal/mol, and 1FSE-Q1: - 3.51 kcal/mol, 1FSE-Q2: - 6.34 kcal/mol). These complexes were simulated at 100 ns and the outcomes revealed their stability with slight conformational changes. Anti-microbial assay via disc diffusion method revealed zones of inhibition showing that B. subtilis was inhibited by both Q1 and Q2, with Q2 performing slightly better than Q1, pointing towards its effectiveness against this organism and necessitating further study on other bacteria in prospective studies. Thus, this study demonstrates that our novel quinoline derivatives exhibit antibacterial properties against Bacillus subtilis and can act as potent anti-bacterials.

Three-Component Synthesis of Quinoline-4-carboxylic Acids Based on Doebner Hydrogen-Transfer Reaction

The Doebner hydrogen-transfer reaction has been developed for the synthesis of substituted quinolines from anilines possessing electron-withdrawing groups, which are known to give products in low yields when used in the conventional Doebner reaction. This reaction can be applied to not only anilines having electron-withdrawing groups but also those having electron-donating groups and can be used in the large-scale synthesis of bioactive molecules.

Palladium-Mediated Synthesis of 2-([Biphenyl]-4-yloxy)quinolin-3-carbaldehydes through Suzuki-Miyaura Cross-Coupling and Their in Silico Breast Cancer Studies on the 3ERT Protein

A series of novel quinoline appended biaryls have been synthesized (5a-5o) by reacting various substituted boronic acids (4e-4h) with various substituted 2-(4-bromophenoxy)quinolin-3-carbaldehydes (3a-3d) through carbon-carbon bond formation. Effects of various quinoline appended biaryls (5a-5o) on the breast cancer protein 3ERT are moderate to high, as found by in silico molecular docking studies. Comparatively, all quinoline appended biaryls (5a-5o) 5h show better efficacy with a binding energy of -9.39 kcal/mol, and hydrogen bonds are Thr347, Glu353, and Arg394 in the binding pocket. Conclusively, the final novel quinoline appended biaryls (5a-5o) have been confirmed with all the spectral studies, and their efficacy has been validated with in silico studies.

Synthesis of antioxidant and antimicrobial bioactive compounds based on the quinoline-hydrazone and benzimidazole structure

Quinoline and its derivatives are known to have various biological activities such as antibacterial and antioxidant. Therefore, this study aims to synthesize quinoline moiety from isatin and ethyl acetoacetate by Pfitzinger reaction under acidic conditions. The benzimidazole derivative was synthesized from quinoline and o-phenylenediamine by a solvent-less reaction, while the hydrazone derivative was formed by the reaction with hydrazine hydrate and aromatic aldehyde. In addition, 4-hydroxybenzaldehyde was used as an aromatic aldehyde. The four compounds formed were characterized by thin-layer chromatography (TLC), melting point measurement, Fourier-transform infrared, liquid chromatography-mass spectrometry, and ultraviolet-visible spectrophotometry. They were also evaluated for their antioxidant and antimicrobial activities using the 2,2-diphenyl-1-picrylhydrazyl assay and the disc diffusion method, respectively. All compounds showed weak antioxidant activity compared to ascorbic acid; the quinoline-hydrazone derivative showed the best antioxidant activity with IC50 = 843.52 ppm, while the IC50 value for quinoline-benzimidazole was 4784.66 ppm. All synthesized compounds have not been confirmed to be effective against Staphylococcus aureus and Escherichia coli bacteria in a concentration range of 75-1000 ppm. The bioactive compounds based on the quinoline-hydrazone and benzimidazole structures have been successfully synthesized and tested for their activity as antioxidant and antimicrobial agents.

Molecular Target Interactions of Quinoline Derivatives as Anticancer Agents: A Review

One of the leading causes of death worldwide is cancer, which poses substantial risks to both society and an individual's life. Cancer therapy is still challenging, despite developments in the field and continued research into cancer prevention. The search for novel anticancer active agents with a broader cytotoxicity range is therefore continuously ongoing. The benzene ring gets fused to a pyridine ring at two carbon atoms close to one another to form the double ring structure of the heterocyclic aromatic nitrogen molecule known as quinoline (1-azanaphthalene). Quinoline derivatives contain a wide range of pharmacological activities, including antitubercular, antifungal, antibacterial, and antimalarial properties. Quinoline derivatives have also been shown to have anticancer properties. There are many quinoline derivatives widely available as anticancer drugs that act via a variety of mechanisms on various molecular targets, such as inhibition of topoisomerase, inhibition of tyrosine kinases, inhibition of heat shock protein 90 (Hsp90), inhibition of histone deacetylases (HDACs), inhibition of cell cycle arrest and apoptosis, and inhibition of tubulin polymerization.

Synthesis and antimalarial activity of 7-chloroquinoline-tethered sulfonamides and their [1,2,3]-triazole hybrids

Aim & background: Drugs with multiple bioactive moieties have the advantages of multiple modes of action and fewer chances of drug resistance. In continuation of our previous work of developing hybrid antimalarials, we present herein the synthesis and antimalarial activity of two different series of 7-chloroquinoline-sulfonamide hybrids. Materials & methods: The first series of compounds were synthesized by using p-dodecylbenzenesulfonic acid as a Bronsted acid catalyst in ethanol. The second series' compounds were synthesized by 1,3-dipolar cycloaddition of azides and alkynes under click reaction conditions. Results & conclusion: The majority of these compounds demonstrated noncytotoxicity and significant antimalarial activity against Plasmodium falciparum (3D7) with IC₅₀ values in the range of 1.49-13.49 μM. The most promising hybrids (12d, 13a and 13c) may be good starting points for next-generation antimalarials.

Novel Polyhydroquinoline-Hydrazide-Linked Schiff's Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (3-27) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (1-27) were deduced with the help of spectroscopic techniques, such as 1H-, 13C -NMR, and HR-ESI-MS. The synthesized products (1-27) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of Escherichia coli and Enterococcus faecalis. Among them, compound 17 was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound 27 was more potent, with an EC50 value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.

Synthesis and Evaluation of the Antibacterial and Antioxidant Activities of Some Novel Chloroquinoline Analogs

Quinoline heterocycle is a useful scaffold to develop bioactive molecules used as anticancer, antimalaria, and antimicrobials. Inspired by their numerous biological activities, an attempt was made to synthesize a series of novel 7-chloroquinoline derivatives, including 2,7-dichloroquinoline-3-carbonitrile (5), 2,7-dichloroquinoline-3-carboxamide (6), 7-chloro-2-methoxyquinoline-3-carbaldehyde (7), 7-chloro-2-ethoxyquinoline-3-carbaldehyde (8), and 2-chloroquinoline-3-carbonitrile (12) by the application of Vilsmeier–Haack reaction and aromatic nucleophilic substitution of 2,7-dichloroquinoline-3-carbaldehyde. The carbaldehyde functional group was transformed into nitriles using POCl3 and NaN3, which was subsequently converted to amide using CH3CO2H and H2SO4. The compounds synthesized were screened for their antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes. Compounds 6 and 8 showed good activity against E. coli with an inhibition zone of 11.00 ± 0.04 and 12.00 ± 0.00 mm, respectively. Compound 5 had good activity against S. aureus and P. aeruginosa with an inhibition zone of 11.00 ± 0.03 mm relative to standard amoxicillin (18 ± 0.00 mm). Compound 7 displayed good activity against S. pyogenes with an inhibition zone of 11.00 ± 0.02 mm. The radical scavenging activity of these compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), and compounds 5 and 6 displayed the strongest antioxidant activity with IC50 of 2.17 and 0.31 µg/mL relative to ascorbic acid (2.41 µg/mL), respectively. The molecular docking study of the synthesized compounds was conducted to investigate their binding pattern with topoisomerase IIβ and E. coli DNA gyrase B. Compounds 6 (−6.4 kcal/mol) and 8 (−6.6 kcal/mol) exhibited better binding affinity in their in silico molecular docking against E. coli DNA gyrase. The synthesized compounds were also found to have minimum binding energy ranging from −6.9 to −7.3 kcal/mol against topoisomerase IIβ. The SwissADME predicted results showed that the synthesized compounds 5–8 and 12 satisfy Lipinski’s rule of five with zero violations. The ProTox-II predicted organ toxicity results revealed that all the synthesized compounds were inactive in hepatotoxicity, immunotoxicity, mutagenicity, and cytotoxicity. The findings of the in vitro antibacterial and molecular docking analysis suggested that compound 8 might be considered a hit compound for further analysis as antibacterial and anticancer drug. The radical scavenging activity displayed by compounds 5 and 6 suggests these compounds as a radical scavenger.

Current Pharmaceutical Aspects of Synthetic Quinoline Derivatives

Quinoline derivatives are considered broad-spectrum pharmacological compounds that exhibit a wide range of biological activities. Integration of quinoline moiety can improve its physical and chemical properties and also pharmacological behavior. Due to its wide range of pharmaceutical applications, it is a very popular compound to design new drugs for the treatment of multiple diseases like cancer, dengue fever, malaria, tuberculosis, fungal infections, AIDS, Alzheimer's disease and diabetes. In this review, our major focus is to pay attention to the biological activities of quinoline compounds in the treatment of these diseases such as anti-viral, anti-cancer, anti-malarial, antibacterial, anti-fungal, anti-tubercular and anti-diabetic.

Novel structural hybrids of quinoline and thiazole moieties: Synthesis and evaluation of antibacterial and antifungal activities with molecular modeling studies

One of the best ways to design new biocidal agents is synthesizing hybrid molecules by combining two or more bioactive moieties in a single molecular scaffold. So, new series of quinolines bearing a thiazole moiety were synthesized using thiosemicarbazones 2a-f. Cyclization of 2a-f with ethyl chloroacetate, ethyl 2-chloropropanoate or chloroacetone afforded the corresponding thiazoles 3-5. The antimicrobial activity of the new quinoline derivatives was evaluated. The most of tested compounds revealed potent both of the antibacterial and antifungal activities. Fourfold potency of amphotericin B for the inhibition the growth of the A. fumigatus was displayed by ccompound 5e. The latter compound displayed twofold potency of gentamycin for inhibition the growth of N. gonorrhoeae. Moreover, this compound showed equipotent potency of references drugs for inhibition of the growth of S. flexneri, S. pyogenes, P. vulgaris, A. clavatus, G. candidum and P. marneffei. So, quinolines bearing a thiazole moiety can be suggested as interesting scaffolds for the development both of the novel antibacterial and antifungal agents. Some new derivatives were studied as peptide deformylase enzyme inhibitors. Thiazolidin-4-one derivative 3d and 2,3-dihydrothiazole derivative 5c had shown good PDF inhibition activity, which had been supported by the docking results with highest binding affinity and lowest docking energy score. These results suggested that the most potent compounds might be possible agents as novel bacterial PDF inhibitor.

Mild and efficient copper-catalyzed oxidative cyclization of oximes with 2-aminobenzyl alcohols at room temperature: synthesis of polysubstituted quinolines

A simple and efficient ligand-free Cu-catalyzed protocol for the synthesis of polysubstituted quinolines via oxidative cyclization of oxime acetates with 2-aminobenzyl alcohols at room temperature has been developed. The presented approach provides a new synthetic pathway leading to polysubstituted quinolines with good functional group tolerance under mild conditions. Moreover, this transformation can be applied for the preparation of quinolines on a gram scale. Oxime acetates serve as the internal oxidants in the reactions, thus making this method very attractive.

Ex vivo potential of a quinoline-derivative nail lacquer as a new alternative for dermatophytic onychomycosis treatment

Introduction. Onychomycosis infections currently show a significant increase, affecting about 10 % of the world population. Trichophyton rubrum is the main agent responsible for about 80 % of the reported infections. The clinical cure for onychomycosis is extremely difficult and effective new antifungal therapy is needed.Hypothesis/Gap Statement. Ex vivo onychomycosis models using porcine hooves can be an excellent alternative for evaluating the efficacy of new anti-dermatophytic agents in a nail lacquer.Aim. Evaluation of the effectiveness of a nail lacquer containing a quinoline derivative on an ex vivo onychomycosis model using porcine hooves, as well as the proposal of a plausible antifungal mechanism of this derivative against dermatophytic strains.Methodology. The action mechanism of a quinoline derivative was evaluated through the sorbitol protection assay, exogenous ergosterol binding, and the determination of the dose-response curves by time-kill assay. Scanning electron microscopy evaluated the effect of the derivative in the fungal cells. The efficacy of a quinoline-derivative nail lacquer on an ex vivo onychomycosis model using porcine hooves was evaluated as well.Results. The quinoline derivative showed a time-dependent fungicidal effect, demonstrating reduction and damage in the morphology of dermatophytic hyphae. In addition, the ex vivo onychomycosis model was effective in the establishment of infection by T. rubrum.Conclusion. Treatment with the quinoline-derivative lacquer showed a significant inhibitory effect on T. rubrum strain in this infection model. Finally, the compound presents high potential for application in a formulation such as nail lacquer as a possible treatment for dermatophytic onychomycosis.

Potential antibacterial and antifungal activities of novel sulfamidophosphonate derivatives bearing the quinoline or quinolone moiety

A series of new α‐sulfamidophosphonate/sulfonamidophosphonate (4a–n) and cyclosulfamidophosphonate (5a–d) derivatives containing the quinoline or quinolone moiety was designed and synthesized via Kabachnik–Fields reaction in the presence of ionic liquid under ultrasound irradiation. This efficient methodology provides new 1,2,5‐thiadiazolidine‐1,1‐dioxide derivatives 5a–d in one step and optimal conditions. The molecular structures of the novel compounds 4a–n and 5a–d were confirmed using various spectroscopic methods. All these compounds were evaluated for their in vitro antibacterial activity against Gram‐negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) and Gram‐positive (Staphylococcus aureus ATCC 27923) bacteria, in addition to three clinical strains (E. coli 1, P. aeruginosa 1, and S. aureus 1). Most of the tested compounds showed more potent inhibitory activities against both Gram‐positive and ‐negative bacteria compared with the sulfamethoxazole reference. The following compounds, 4n, 4f, 4g, 4m, 4l, 4d, and 4e, are the most active sulfamidophosphonate derivatives. Furthermore, these molecules gave interesting zones of inhibition varying between 28 and 49 mm, against all tested bacterial strains, with a low minimum inhibitory concentration (MIC) value ranging from 0.125 to 8 μg/ml. All the synthesized derivatives were also evaluated for their in vitro antifungal activity against Fusarium oxyporum f. sp. lycopersici and Alternaria sp. The results revealed that all the synthesized compounds exhibited excellent antifungal inhibition and the compounds 4f, 4g, 4m, and 4i were the most potent derivatives with MIC values ranging from 0.25 to 1 µg/ml against the two tested fungal strains. The strongest inhibition of bacteria and fungi strains was detected by the effect of quinolone and sulfamide moieties.

Recent update on antibacterial and antifungal activity of quinoline scaffolds

Although most of the heterocycles have been reported to possess a significant pharmacological activity, only a few of them, namely quinoline derivatives, have exhibited the finest biological activities. Despite the few medicinal properties of the plain quinoline molecule, its derivatives exhibit diverse pharmacological properties such as anticancer, anti-inflammatory, antibacterial, antiviral, antifungal, antiprotozoal activities, and so on. The potential antimicrobial properties of the quinoline derivatives are evident from the decades of research on these derivatives. Owing to limitations like drug resistance, high cost, severe side effects, and less bioavailability of previously synthesized antimicrobial agents, these drugs have become obsolete in recent years. Hence, the design of more efficient antimicrobial drugs must be given topmost priority. A breakthrough in drug discovery is a must to prevent malevolent microbial diseases. Addressing all these issues, researchers have been continuously contributing to antimicrobial drug discovery. Herein, a short description of the pharmacology of antimicrobial agents such as antibacterials and antifungals synthesized recently is provided. The versatile derivatization of the quinoline moiety leading to significant antimicrobial potencies is discussed, considering the structure-activity relationship.

An Updated Review on the Synthesis and Antibacterial Activity of Molecular Hybrids and Conjugates Bearing Imidazole Moiety

The rapid growth of serious infections caused by antibiotic resistant bacteria, especially the nosocomial ESKAPE pathogens, has been acknowledged by Governments and scientists and is one of the world's major health problems. Various strategies have been and are currently investigated and developed to reduce and/or delay the bacterial resistance. One of these strategies regards the design and development of antimicrobial hybrids and conjugates. This unprecedented critical review, in which our continuing interest in the synthesis and evaluation of the bioactivity of imidazole derivatives is testified, aims to summarise and comment on the results obtained from the end of the 1900s until February 2020 in studies conducted by numerous international research groups on the synthesis and evaluation of the antibacterial properties of imidazole-based molecular hybrids and conjugates in which the pharmacophoric constituents of these compounds are directly covalently linked or connected through a linker or spacer. In this review, significant attention was paid to summarise the strategies used to overcome the antibiotic resistance of pathogens whose infections are difficult to treat with conventional antibiotics. However, it does not include literature data on the synthesis and evaluation of the bioactivity of hybrids and conjugates in which an imidazole moiety is fused with a carbo- or heterocyclic subunit.

Acylacetylenes in multiple functionalization of hydroxyquinolines and quinolones

The expected one-pot multiple functionalization of hydroxyquinolines and quinolones with acylacetylenes (20 mol% KOH, 5 equiv. H₂O, MeCN, 55-60 °C), which, according to the previous finding, might involve the addition of OH and NH-functions to the triple bond and insertion of acylacetylenes into the quinoline scaffold, retains mainly on the formation of chalcone-quinoline ensembles in up 99% yield. The higher functionalized quinolines can be obtained in a synthetically acceptable yield, when the above ensembles are treated with the second molecule of acylacetylenes. Thus, the further insertion of second molecule of the acetylenes into the quinoline scaffold occurs as a much slower process indicating a strong adverse substituent effect of the remote chalcone moiety.

Quinolines derivatives as promising new antifungal candidates for the treatment of candidiasis and dermatophytosis

Fungal infections have emerged as a current serious global public health problem. The main problem involving these infections is the expansion of multidrug resistance. Therefore, the prospection of new compounds with efficacy antifungal becomes necessary. Thus, this study evaluated the antifungal profile and toxicological parameters of quinolines derivatives against Candida spp. and dermatophyte strains. As a result, a selective anti-dermatophytic action was demonstrated by compound 5 (geometric means (GM = 19.14 μg ml⁻¹)). However, compounds 2 (GM = 50 μg ml⁻¹) and 3 (GM = 47.19 μg ml⁻¹) have presented only anti-Candida action. Compounds 3 and 5 did not present cytotoxic action. Compound 5 did not produce dermal and mucosal toxicity. In addition, this compound showed the absence of genotoxic potential, suggesting safety for topical and systemic use. Quinolines demonstrated a potent anti-dermatophytic and anti-yeast action. Moreover, compound 5 presented an excellent toxicological profile, acting as a strong candidate for the development of a new effective and safe compound against dermatophytosis of difficult treatment.

Tetrazolo[1,5-a]quinoline moiety-based Os(IV) complexes: DNA binding/cleavage, bacteriostatic and photocytotoxicity assay

Biological applications of platinum group metal-based complexes have been widely explored in synthetic and inorganic chemistry. The compounds have been subjected to DNA binding, DNA cleavage, In-vivo and In-vitro photocytotoxicity (HCT-116 cell line) and bacteriostatic activities. Binding constant of complexes are 1.42-5.62 × 10⁴ M^-1, whereas that of ligands are 1.12-4.72 × 10⁴ M^-1. K_sv of complexes are about 1.32-5.21 × 10³ M^-1, whereas K_f is about 1.24-6.83 × 10³ M^-1. IC₅₀ of compounds screened using HCT-116 cell line in dark are found to be 121-342 μg/mL. Whereas photocytotoxicity is found in the range of 48-316 μg/mL. Docking energy of molecules have been evaluated to evaluate efficacy of binding. Molecular docking energy of complexes are in the range of -286.00 to -303.11 kJ/mol. Whereas that of ligands are -254.03 to -282.96 kJ/mol. MIC of complexes are 47 ± 2.5 to 77.50 ± 7.5 μM. LC₅₀ values of ligands fall in the range of 4.05-19.72 μg/mL and that of Os(IV) complexes fall in the range of 3.99-15.99 μg/mL. The Os(IV) complexes dominate in proving its potentiality compared to N, N-donor ligands in biological activities. [Formula: see text]Communicated by Ramaswamy H. Sarma.

A review on quinoline derivatives as anti-methicillin resistant Staphylococcus aureus (MRSA) agents

Methicillin Resistant Staphylococcus aureus (MRSA) consists of strains of S. aureus which are resistant to methicillin. The resistance is due to the acquisition of mecA gene which encodes PBP2a unlike of any PBPs normally produced by S. aureus. PBP2a shows unusually low β-Lactam affinity and remains active to allow cell wall synthesis at normally lethal β-Lactam concentrations. MRSA can cause different types of infections like Healthcare associated MRSA, Community associated MRSA and Livestock associated MRSA infections. It causes skin lesions, osteomyelitis, endocarditis and furunculosis. To treat MRSA infections, only a few options are available like vancomycin, clindamycin, co-trimoxazole, fluoroquinolones or minocycline and there is a dire need of discovering new antibacterial agents that can effectively treat MRSA infections. In the current review, an attempt has been made to compile the data of quinoline derivatives possessing anti-MRSA potential reported to date.

Anticancer, antimicrobial activities of quinoline based hydrazone analogues: Synthesis, characterization and molecular docking

Based on the biologically active heterocycle quinoline, a series (18a-p) of quinoline hydrazone analogues were prepared, starting from 6-bromo/6-chloro-2-methyl-quinolin-4-yl-hydrazines. For all the newly synthesized compounds cytotoxic activities were carried out at the National Cancer Institute (NCI), USA, against full NCI 60 human cancer cell lines. Amongst all the tested compounds, nine compounds (18b, 18d, 18e, 18f, 18g, 18h, 18i, 18j, 18l) exhibited important anti-proliferative activity at 10 µM concentration and were further screened at 10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10 and 100 µM) with GI₅₀ values ranging from 0.33 to 4.87 µM and LC₅₀ values ranging from 4.67 µM to >100j µM. Further, the mean values of GI₅₀, TGI and LC₅₀ of the most potent compound 18j were compared with the clinically used anticancer agents bendamustine and chlorambucil, revealed that the quinolyl hydrazones holds promise as a potential anticancer agents. Further all the newly prepared compounds were screened for their antimicrobial activity. All the quinolyl hydrazones displayed good to excellent antimicrobial activity with MIC values ranging from 6.25 to 100 µg/mL against the tested pathogenic strains. Molecular docking of the synthesized compounds into the active binding site of human DNA topoisomerase I (htopoI) was carried out to predict the binding mode to the DNA topoisomerase I inhibitors. Hopefully in future, compounds based on quinoline core could be used as a lead compounds for designing new anticancer agents.

Synthesis and Study of New Quinolineaminoethanols as Anti-Bacterial Drugs

The lack of antibiotics with a novel mode of action associated with the spread of drug resistant bacteria make the fight against infectious diseases particularly challenging. A quinoline core is found in several anti-infectious drugs, such as mefloquine and bedaquiline. Two main objectives were set in this work. Firstly, we evaluated the anti-mycobacterial properties of the previous quinolines 3, which have been identified as good candidates against ESKAPEE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli) bacteria. Secondly, a new series 4 was designed and assessed against the same bacteria strains, taking the pair of enantiomers 3m/3n as the lead. More than twenty compounds 4 were prepared through a five-step asymmetric synthesis with good enantiomeric excesses (>90%). Interestingly, all compounds of series 3 were efficient on M. avium with MIC = 2-16 µg/mL, while series 4 was less active. Both series 3 and 4 were generally more active than mefloquine against the ESKAPEE bacteria. The quinolines 4 were either active against Gram-positive bacteria (MIC ≤ 4 µg/mL for 4c-4h and 4k/4l) or E. coli (MIC = 32-64 µg/mL for 4q-4v) according to the global lipophilicity of these compounds.

Choline Chloride-Based Deep Eutectic Systems in Sequential Friedländer Reaction and Palladium-Catalyzed sp3 CH Functionalization of Methyl Ketones

A volatile organic solvent-free and choline chloride (ChCl)-based deep eutectic system (DES)-mediated sp³-CH functionalization of acetophenones 1 with benzyl alcohols 2 to the corresponding α, β-saturated ketones 3 is accounted for. The domino dehydrogenation-aldol condensation (hydrogenation borrowing concept) has been successfully attempted with palladium-tetrakis(triphenylphosphine) [Pd(PPh₃)₄] catalyst-xantphos ligand combination. Furthermore, a sequential Friedländer reaction of 2-aminobenzophenone 4 and palladium-catalyzed α-alkylation of the quinolinyl methyl ketone with benzyl alcohols 2 in ChCl-based DES have been successfully investigated. The C-C bond formation through sp³-CH functionalization involves a wide scope of the substrates, high atom efficiency, chemoselectivity, and environmentally friendly strategy.