Hybrid Quinoline-Sulfonamide Complexes (M2+) Derivatives with Antimicrobial Activity

Ultrasound assisted synthesis of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety with potential antimicrobial activity

We present in this paper a direct and efficient study regarding synthesis and spectral characterization of three series of hybrid quinoline anchored with 4-R-benzenesulfonamide moiety, with potential antimicrobial activity, by using ultrasound (US) irradiation and conventional methods (CV). The synthesis pathway is efficient and direct, in two steps: an initial N-acylation of 8-aminoquinoline followed by metal complexation with variously M2+ metals (Cd2+, Co2+, Cu2+, Ni2+, Pd2+, Zn2+). For both type of reactions, N-acylation and complexation, under US irradiations the synthesis have some undeniable advantages: the most relevant being the higher yields, a dramatically decrease for reaction time (with about 150 (one hundred fifty) folds for complexation) comparative with conventional methods (CV) (therefore the spent energy decrease in the same way), a decrease of the amount of used solvents. Taking into account the above considerations these reactions setup could be appreciated as eco-friendly. The structures of the obtained hybrid quinoline - sulfonamide complexes (HQBSM) were determined by elemental analysis and by using spectral investigations: FT-IR, NMR experiments, and X-ray diffraction (in three cases). The FT-IR and NMR spectra of complexes show a similar spectroscopic pattern for all complexes and fully confirm the proposed structures. The X-ray spectra analyses prove without doubts the structure of metal complexes, indicating that their structure depends essentially by two factors: the nature of metal and the nature of sulfonamide-quinoline moieties. Complexes containing 4-methoxy-benzoyl moiety and Zn2+ (e.g. 6a) are tetra-coordinated while in the Ni2+ complex (e.g. 6e) the metallic ion forms a distorted square-based bi-pyramid. In the complexes containing 4-nitro-benzoyl moiety and Cd2+ (e.g. 5d) the metallic ion forms a triangular bipyramid. The antibacterial and antifungal assay reveal that only hybrid HQBSM complex (4e) (with 4-chlorophenyl moiety and Ni2+ in molecule) have a significant antibacterial activity.

Synthesis of ruthenium polypyridine complexes with benzyloxyl groups and their antibacterial activities against Staphylococcus aureus

Four new ruthenium polypyridyl complexes, [Ru(bpy)₂(BPIP)](PF₆)₂ (Ru(II)-1), [Ru(dtb)₂(BPIP)](PF₆)₂ (Ru(II)-2), [Ru(dmb)₂(BPIP)](PF₆)₂ (Ru(II)-3) and [Ru(dmob)₂(BPIP)](PF₆)₂ (Ru(II)-4) (bpy = 2,2'-bipyridine, dtb = 4,4'-di-tert-butyl-2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine, dmob = 4,4'-dimethoxy-2,2'-bipyridine and BPIP = 2-(3,5-bis(benzyloxyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) had been synthesized and characterized. Their antimicrobial activities were investigated against Staphylococcus aureus (S. aureus) and four complexes showed obvious antibacterial effect, especially the minimum inhibition concentration (MIC) value of Ru(II)-3 was only 4 μg/mL. In addition, Ru(II)-3 was able to kill bacteria quickly and inhibit the formation of biofilm. Meanwhile, the cooperative effect between Ru(II)-3 and general antibiotics were tested and the results showed that Ru(II)-3 could enhance the susceptibility of S. aureus to different types of antibiotics. Most importantly, Ru(II)-3 hardly showed cytotoxicity to mammalian erythrocytes both in homelysis experiment and G. mellonella model. After being injected with high doses of the Ru(II)-3in vivo, the G. mellonella worms still exhibited high survival rates. Finally, a mouse skin infection model and G. mellonella infection model was built to determine the antibacterial activity of Ru(II)-3in vivo. The antibacterial mechanism of Ru(II)-3 was probably related to the membrane-disruption. Taken together, ruthenium polypyridine complexes with benzyloxyl groups had the potential to develop an attractive and untraditional antibacterial agent with new mode of action.

Quinoline-imidazole/benzimidazole derivatives as dual-/multi-targeting hybrids inhibitors with anticancer and antimicrobial activity

Two new classes of hybrid quinoline-imidazole/benzimidazole derivatives (the hybrid QIBS salts and QIBC cycloadducts) were designed and synthesized to evaluate their anticancer and antimicrobial activity. The strategy adopted for synthesis is straight and efficient, in four steps: N-acylation, N-alkylation, quaternization and a Huisgen 3 + 2 cycloaddition. The in vitro single-dose anticancer assay of forty six hybrid quinoline-benzimidazole compounds reveal that one QIBS salt (11h), has an excellent quasi nonselective activity against all type of cancer cell with an excellent PGI in the area of 90-100% and very good lethality. Three others quinoline-imidazole/benzimidazole hybrids (8h, 12h, 12f) has an excellent selective activity against some cancer cell lines: breast cancer MDA-MB-468 and Leukemia HL-60 TB). The five-dose assay screening confirms that compound 11h possesses excellent anti-proliferative activity, with GI₅₀ in the range of nano-molar, against some cancer cell lines: Leukemia HL-60 TB, Leukemia K-526, Leukemia RPMI-8226, Breast cancer MDA-MB-468, Lung cancer HOP-92 and Ovarian cancer IGROV1. The antibacterial assay indicates that three hybrid QIBS salts (12f, 12c, 12d) have an excellent activity against Gram-negative bacteria E. coli (superior to control Gentamicin) while against Gram-positive bacteria S. aureus only one compound 8i (R₂ = -CF3) exhibits a significant activity (superior to control Gentamicin). The MIC assay indicates that two other compounds (11h, 12h) are biologically active to a very low concentration, in the range of nano-molar. We believe that all these excellent assets related to anticancer and antibacterial activities, make from our hybrid quinoline-imidazole/benzimidazole compounds bearing a phenyl group (R₂ = -C₆H₅) in the para (4)-position of the benzoyl moiety a good candidate for future drug developing.

Hybrid Azine Derivatives: A Useful Approach for Antimicrobial Therapy

Nowadays, infectious diseases caused by microorganisms are a major threat to human health, mostly because of drug resistance, multi-drug resistance and extensive-drug-resistance phenomena to microbial pathogens. During the last few years, obtaining hybrid azaheterocyclic drugs represents a powerful and attractive approach in modern antimicrobial therapy with very promising results including overcoming microbial drug resistance. The emphasis of this review is to notify the scientific community about the latest recent advances from the last five years in the field of hybrid azine derivatives with antimicrobial activity. The review is divided according to the main series of six-member ring azaheterocycles with one nitrogen atom and their fused analogs. In each case, the main essential data concerning synthesis and antimicrobial activity are presented.

An overview of sulfonamide-based conjugates: Recent advances for tuberculosis treatment

In 2019, tuberculosis (TB) caused approximately 1.4 million deaths around the world. TB is an infectious respiratory disease mainly caused by Mycobacterium tuberculosis. The lack of new drugs to treat drug-resistant strains is a principal factor for the continuous slow rise in TB infections. Sulfonamides are active moieties in various drugs used against several sicknesses, including TB. Our aim is to aid the development of new TB treatments and drugs by describing recent improvements (2011-2021) to sulfonamide-based compounds.

Design and synthesis of ciprofloxacin-sulfonamide hybrids to manipulate ciprofloxacin pharmacological qualities: Potency and side effects

Fluoroquinolones are a class of antibacterial agents used clinically to treat a wide array of bacterial infections. Although being potent, susceptibility to CNS side effects limits their use. It was observed that improvements in absorption, activity and side effects were achieved via modifications at the N atom of the C7 of the side chain. To meet the increasing demand for development of new antibacterial agents, nineteen novel ciprofloxacin-sulfonamide hybrid molecules were designed, synthesized and characterized by IR, ¹H NMR and ¹³C NMR as potential antibacterial agents with dual DNA gyrase/topoisomerase IV inhibitory activity. Most of the synthesized compounds showed significant antibacterial activity that was revealed by testing their inhibitory activity against DNA gyrase, DNA topoisomerase IV as well as their minimum inhibitory concentration against Staphylococcus aureus. Six ciprofloxacin-sulfonamide hybrids (3f, 5d, 7a, 7d, 7e and 9b) showed potent inhibitory activity against DNA topoisomerase IV, compared to ciprofloxacin (IC50: 0.55 μM), with IC50 range: 0.23-0.44 μM. DNA gyrase was also efficiently inhibited by five ciprofloxacin-sulfonamide hybrids (3f, 5d, 5e, 7a and 7d) with IC50 range: 0.43-1.1 μM (IC50 of ciprofloxacin: 0.83 μM). Compounds 3a and 3b showed a marked improvement in the antibacterial activity over ciprofloxacin against both Gram-positive and Gram-negative pathogens, namely, Staphylococcus aureus Newman and Escherichia coli ATCC8739, with MIC = 0.324 and 0.422 μM, respectively, that is 4.2-fold and 3.2-fold lower than ciprofloxacin (MIC = 1.359 μM) against the Gram-positive Staphylococcus aureus, and MIC = 0.025 and 0.013 μM, respectively, that is 10.2-fold and 19.6-fold lower than ciprofloxacin (MIC = 0.255 μM) against the Gram-negative Escherichia coli ATCC8739. Also, the most active compounds showed lower CNS and convulsive side effects compared to ciprofloxacin with a concomitant decrease in GABA expression.

Discovery of metal-based complexes as promising antimicrobial agents

The antimicrobial resistance (AMR) is an intractable problem for the world. Metal ions are essential for the cell process and biological function in microorganisms. Many metal-based complexes with the potential for releasing ions are more likely to be absorbed for their higher lipid solubility. Hence, this review highlights the clinical potential of organometallic compounds for the treatment of infections caused by bacteria or fungi in recent five years. The common scaffolds, including antimicrobial peptides, N-heterocyclic carbenes, Schiff bases, photosensitive-grand-cycle skeleton structures, aliphatic amines-based ligands, and special metal-based complexes are summarized here. We also discuss their therapeutic targets and the risks that should be paid attention to in the future studies, aiming to provide information for researchers on metal-based complexes as antimicrobial agents and inspire the design and synthesis of new antimicrobial drugs.

Benzoquinoline Derivatives: A Straightforward and Efficient Route to Antibacterial and Antifungal Agents

We report here the design, synthesis, experimental and in silico evaluation of the antibacterial and antifungal activity of some new benzo[f]quinoline derivatives. Two classes of benzo[f]quinolinium derivatives—(benzo[f]quinolinium salts (BQS) and pyrrolobenzo[f]quinolinium cycloadducts (PBQC)—were designed and obtained in two steps via a direct and facile procedure: quaternization followed by a cycloaddition reaction. The synthesized compounds were characterized by elemental and spectral analysis (FT-IR, ¹H-NMR, ¹³C-NMR). The antimicrobial assay reveals that the BQS salts have an excellent quasi-nonselective antifungal activity against the fungus Candida albicans (some of them higher that the control drug nystatin) and very good antibacterial activity against the Gram positive bacterium Staphylococcus aureus. The PBQC compounds are inactive. Analysis of the biological data reveals interesting SAR correlations in the benzo[f]quinolinium series of compounds. The in silico studies furnished important data concerning the pharmacodynamics, pharmacokinetics and ADMET parameters of the BQS salts. Studies of the interaction of each BQS salt 3a–o with ATP synthase in the formed complex, reveal that salts 3j, 3i, and 3n have the best fit in a complex with ATP synthase. Study of the interaction of each BQS salt 3a-o with TOPO II in the formed complex reveals that salts 3j and 3n have the best-fit in complex with TOPO II. The in silico ADMET studies reveal that the BQS salts have excellent drug-like properties, including a low toxicity profile. Overall, the experimental and in silico studies indicate that compounds 3e and 3f (from the aliphatic series), respectively, and 3i, 3j and 3n (from the aromatic series), are promising leading drug candidates.

Folic acid-sulfonamide conjugates as antibacterial agents: design, synthesis and molecular docking studies

Dihydrofolate reductase (DHFR) inhibitors, as antibacterial agents, contain pyrimidine, pteridine, and azine moieties among many other scaffolds. Folic acid (FA), with a pteridine ring and amine group, was used as our focus scaffold, which was then conjugated with sulfonamides to develop new conjugates. The novel synthesized conjugates were characterized using infrared spectroscopy, and ¹H and ¹³C nuclear magnetic resonance (NMR) spectral studies and consequently screened for antimicrobial activities against bacterial strains with ampicillin as a positive control. Compound DS2 has the highest zone of inhibition (36.6 mm) with a percentage activity index (%AI) value of 122.8% against S. aureus and a minimum inhibitory concentration (MIC) of 15.63 μg mL^-1. DHFR enzyme inhibition was also evaluated using the synthesized conjugates through in vitro studies, and inhibition assays revealed that compound DS2 exhibited a 75.4 ± 0.12% (mean ± standard error of the mean (SEM)) inhibition, which is comparable with the standard DHFR inhibitor trimethoprim (74.6 ± 0.09%). The compounds attached to the unsubstituted aryl moiety of the sulfonamides revealed better inhibition against the bacterial strains as compared to the methyl substituted aryl sulfonamides. Molecular docking studies of the novel synthesized conjugates were also performed on the DHFR enzyme to identify the plausible binding modes to explore the binding mechanisms of these conjugates.