Design, Synthesis and Biological Evaluation of 1-Ethyl-3-(thiazol-2-yl)urea Derivatives as Escherichia coli DNA Gyrase Inhibitors

Peer reviewe

New N-phenyl-4,5-dibromopyrrolamides as DNA gyrase B inhibitors

Due to the rapid development of antimicrobial resistance, the discovery of new antibacterials is essential in the fight against potentially lethal infections. The DNA gyrase B (GyrB) subunit of bacterial DNA gyrase is an excellent target for the design of antibacterials, as it has been clinically validated by novobiocin. However, there are currently no drugs in clinical use that target GyrB. We prepared a new series of N-phenyl-4,5-dibromopyrrolamides and evaluated them against DNA gyrase and against the structurally and functionally similar enzyme, topoisomerase IV. The most active compound, 28, had an IC50 of 20 nM against Escherichia coli DNA gyrase. The IC50 values of 28 against Staphylococcus aureus DNA gyrase, and E. coli and S. aureus topoisomerase IV were in the low micromolar range. However, the compounds evaluated did not show significant antibacterial activities against selected Gram-positive and Gram-negative bacteria. Our results indicate that for potent inhibition of DNA gyrase, a combination of polar groups on the carboxylic end of the molecule and substituents that reach into the 'lipophilic floor' of the enzyme is required.Peer reviewe

A new cell-based AI-2-mediated quorum sensing interference assay in screening of LsrK-targeted inhibitors

Quorum sensing (QS), a bacterial communication strategy, has been recognized as one of the control mechanisms of virulence in bacteria. Thus, targeting QS offers an interesting opportunity to impair bacterial pathogenicity and develop antivirulence agents. Aiming to enhance the discovery of QS inhibitors, we developed a bioreporter Escherichia coli JW5505 pET-Plsrlux and set up a cell-based assay for identifying inhibitors of autoinducer-2 (AI-2)-mediated QS. A comparative study on the performance of target- versus cell-based assays was performed, and 91 compounds selected with the potential to target the ATP binding pocket of LsrK, a key enzyme in AI-2 processing, were tested in an LsrK inhibition assay, providing 36 hits. The same set of compounds was tested by the AI-2-mediated QS interference assay, resulting in 24 active compounds. Among those, six were also found to be active against LsrK, whereas 18 might target other components of the pathway. Thus, this AI-2-mediated QS interference cell-based assay is an effective tool for complementing target-based assays, yet also stands as an independent assay for primary screening.Peer reviewe

Design, synthesis and biological evaluation of novel DNA gyrase Inhibitors and their siderophore mimic conjugates

Bacterial DNA gyrase is an important target for the development of novel antibacterial drugs, which are urgently needed because of high level of antibiotic resistance worldwide. We designed and synthesized new 4,5,6,7-tetrahydrobenzo[d]thiazole-based DNA gyrase B inhibitors and their conjugates with siderophore mimics, which were introduced to increase the uptake of inhibitors into the bacterial cytoplasm. The most potent conjugate 34 had an IC50 of 58 nM against Escherichia coli DNA gyrase and displayed MIC of 14 mu g/mL against E. coli.tolC strain. Only minor improvements in the antibacterial activities against wild-type E. coli in low-iron conditions were seen for DNA gyrase inhibitor - siderophore mimic conjugates.Peer reviewe

Design, synthesis and biological evaluation of 4,5-dibromo-N-(thiazol-2-yl)-1H-pyrrole-2-carboxamide derivatives as novel DNA gyrase inhibitors

Development of novel DNA gyrase B inhibitors is an important field of antibacterial drug discovery whose aim is to introduce a more effective representative of this mechanistic class into the clinic. In the present study, two new series of Escherichia coli DNA gyrase inhibitors bearing the 4,5-dibromopyrrolamide moiety have been designed and synthesized. 4,5,6,7-Tetrahydrobenzo[1,2-d] thiazole-2,6-diamine derivatives inhibited E. coli DNA gyrase in the submicromolar to low micromolar range (IC50 values between 0.891 and 10.4 mu M). Their "ring-opened" analogues, based on the 2-(2-aminothiazol-4-yl) acetic acid scaffold, displayed weaker DNA gyrase inhibition with IC50 values between 15.9 and 169 mu M. Molecular docking experiments were conducted to study the binding modes of inhibitors. (C) 2016 Elsevier Ltd. All rights reserved.Peer reviewe

Estimation of gastrointestinal absorption of a series of dual DNA Gyrase and Topoisomerase IV inhibitors using Pampa technique

In this study, estimation of gastrointestinal absorption of thirteen selected dual DNA gyrase and topoisomerase IV inhibitors was carried out using PAMPA test. Diffusion through artificial membrane, consisting of egg lecithin solution in dodecane (first PAMPA model) and a mixture of hexadecane and hexane (second PAMPA model), was monitored [1,2]. The starting solutions (pH 5.5) and the acceptor medium (pH 7.4) were prepared to contain 2% dimethyl sulfoxide. Concentrations of tested compounds in starting solutions, donor and acceptor medium after incubation were measured using LC-MS/MS method. Permeability coefficients were calculated and good correlation was observed between results obtained using these two PAMPA models. Subsequently, the hexadecane/hexane model was selected for the evaluation of gastrointestinal absorption of the remaining ten compounds. Derivatives with the highest permeability in hexadecane/hexane model were TZS-34 and TCF-3a (logPe: -5.37 and -4.93, respectively) whereas TLK-13 and NZ-97 had the lowest permeability (logPe: -9.91 and -9.85, respectively). Therefore, the highest gastrointestinal absorption can be expected from TZS-34 and TCF-3a, and lowest from TLK-13 and NZ-97 (Figure 1). High membrane retention observed for compounds TEL-28 (72%) and TAZ-2b (30 %) might be a reason for lower permeability than expected based on their lipophilicity

RP-HPLC evaluation of lipophilicity of a series of dual DNA gyrase and topoisomerase IV inhibitors

In this study, lipophilicity of twenty-three DNA gyrase and topoisomerase IV ATPase inhibitors was estimated at two pH values (5.5 and 7.4) using reversed-phase high-performance liquid chromatography (RP-HPLC) [1,2]. Retention behavior was tested on HP 1100 HPLC chromatograph, using column Zorbax Eclipse Plus C8 (150 X 4.6 mm, 5 µm particle size). Mobile phase consisted of acetonitrile and phosphate buffer (pH was adjusted to 5.5 or 7.4). Each compound was tested in four different ratios of acetonitrile and buffer (acetonitrile ranged from 20% to 65%). Column temperature was 25 °C, flow rate 1 mL/min, injection volume 20 µL and detection was performed at 254 nm. For each compound, capacity factor (k) was calculated and logk values were plotted against percentage of acetonitrile. Finally, following chromatography parameters were calculated: logkw (y-axis intercept), a (slope) and ϕ0 (-logkw/a). Derivatives with the highest lipophilicity were TEL-28 and NDL-20, whereas NZ97 had the lowest lipophilicity (at both pH values, Figure 1). The majority of compounds possess similar or slightly different lipophilicities at both pH values, but the highest differences were observed for TAZ-7, LMD-17 and NCH-4d, which could significantly affect their biological properties (particularly gastrointestinal absorption, distribution and biological activity)