Synthesis and antitubercular evaluation of 2-iminothiazolidine-4-ones

In the present manuscript, we report synthesis of new 3 and 5 substituted 2-imino thiazolidine-4-ones by three step synthetic protocols from 3-trifluormethyl aniline or 2-amino heterocycle. The compounds were evaluated for in vitro activities against Mycobacterium tuberculosis (MTB) in presence and absence of efflux pump inhibitor, cytotoxicity against RAW 264.7 cells. Among the thirty six compounds, 2-imino-3-(5-nitrothiazol-2-yl)-5-(3,4,5-trimethoxybenzylidene)thiazolidin-4-one (5g) was found to be the most active compound in vitro with MICs of 3.31 µM against log-phase culture of MTB and also non-toxic up to 100 µM. Compound 5g showed minimum inhibitory concentration (MIC) of 0.82 µM against MTB in presence of efflux pump inhibitor verapamil

Optimization and validation of Mycobacterium marinum-induced adult zebrafish model for evaluation of oral anti-tuberculosis drugs

Introduction: Mycobacterium marinum has emerged as a suitable species for induction of tuberculosis-like disease in zebrafish, and various zebrafish models (larval and adult) for drug screening have been proposed in the literature. It is believed that an adult zebrafish model is more useful in drug screening because, apart from assessment of efficacy, one can obtain data on dosage, pharmacokinetics and overall health improvement. This study suggests a simple, cost-effective and resource-efficient protocol for screening of anti-tuberculosis drugs. Methods: The parameters used for assessment of infection as well as anti-bacterial response were: (a) bacterial count; and (b) body weight change. An optimization study was conducted to establish the concentration of bacteria required to produce a reproducible phenotype of tuberculosis (TB). A negative control (Amoxicillin) and anti-mycobacterial drugs (Isoniazid, Rifampicin, Moxifloxacin, Ethambutol and Isoniazid+Rifampicin) were used for validation of the protocol. All the drugs were administered orally. Results: An intra-peritoneal inoculation of 0.75 million bacteria/fish was optimized for the model. All the anti-tuberculosis drugs showed efficacy in this model, whereas the negative control did not show any signs of reversing the parameters of M. marinum infection. Discussion: Adult zebrafish model of M. marinum-induced tuberculosis has not been fully exploited as a drug screening tool. In the present report, a protocol is suggested that is simple, reproducible and resource-efficient for screening of anti-tuberculosis agents. This protocol is an attempt to refine the published protocols and use this model as a surrogate model of human TB for the purpose of drug screening

Benzothiazinone-piperazine derivatives as efficient Mycobacterium tuberculosis DNA gyrase inhibitors

Background and objectives: Bacterial DNA topoisomerases are unique in maintaining the DNA topology for cell viability. Mycobacterium tuberculosis (MTB) DNA gyrase, a sole type II topoisomerase has a larger scope as a target for developing novel therapeutics. In this study, an effort was made towards the design and synthesis of benzothiazinone-piperazine hybrid analogues to obtain the possibility of it to lead development through the molecular hybridization technique. Methods: A five-step scheme was followed to obtain a series of 36 benzothiazinone-piperazine derivatives and to evaluate them for Mtb DNA gyrase inhibition, antimycobacterial and cytotoxicity studies. Results: Compound N-(4-chlorophenyl)-4-(6-nitro-4-oxo-4H-benzo[e][1,3]thiazin-2-yl)piperazine-1-carbothioamide (18) showed greater inhibitory potential with an IC50 of 0.51±0.16 μM in the DNA supercoiling assay of Mtb with a moderate anti-tubercular activity of 4.41 μM. The compound even passed the safety profile of eukaryotic cell cytotoxicity with a 1.81% inhibition in the RAW 264.7 cell line at 100 μM concentration. Conclusions: This study describes the discovery of benzothiazinone as gyrase inhibitors with potent Mtb MIC and inhibitory profiles of the gyrase enzyme with less cytotoxic effect. Furthermore, it is believed that this class of compounds has the potential to be further developed as an anti-TB drug candidate

Investigating structure–activity relationship and mechanism of action of antitubercular 1-(4-chlorophenyl)-4-(4-hydroxy-3-methoxy-5-nitrobenzylidene) pyrazolidine-3,5-dione [CD59]

Background and objectives: The objective of this study is to synthesize and evaluate 1-(4-chlorophenyl)-4-(4-hydroxy-3-methoxy-5-nitrobenzylidene) pyrazolidine-3,5-dione (CD59) analogues to establish structure–activity relationship and mechanism of action. Methods: Thirty analogues of reported antitubercular CD59 were prepared by two-step synthetic protocols and characterized. The compounds were evaluated for in vitro activities against Mycobacterium tuberculosis (MTB), cytotoxicity against RAW 264.7 cells. The molecules were also evaluated for three mycobacterial enzymes to study the mechanism of action. Results: Among the compounds, 4-(2-bromobenzylidene)-1-(4-chlorophenyl)pyrazolidine-3,5-dione (4k) was found to be the most active compound in vitro with MICs of 4.13 μM against log-phase culture of MTB and also non-toxic up to 50 μM. Conclusions: Amongst all, the compounds 4g, 3i and 3n were most active against the enzymes MTB Pantothenate synthetase, lysine amino transferase and Alanine dehydrogenase, respectively. Further screening of these molecules was required in the in vitro dormant MTB models

Benzo[d]thiazol-2-yl(piperazin-1-yl)methanones as new anti-mycobacterial chemotypes: design, synthesis, biological evaluation and 3D-QSAR studies

The benzo[d]thiazol-2-yl(piperazin-1-yl)methanones scaffold has been identified as new anti-mycobacterial chemotypes. Thirty-six structurally diverse benzo[d]thiazole-2-carboxamides have been prepared and subjected to assessment of their potential anti-tubercular activity through in vitro testing against Mycobacterium tuberculosis H37Rv strain and evaluation of cytotoxicity against RAW 264.7 cell lines. Seventeen compounds showed anti-mycobacterial potential having MICs in the low (1–10) μM range. The 5-trifluoromethyl benzo[d]thiazol-2-yl(piperazin-1-yl)methanones emerged to be the most promising resulting in six positive hits (2.35–7.94 μM) and showed low-cytotoxicity (<50% inhibition at 50 μg/mL). The therapeutic index of these hits is 8–64. The quantitative structure activity relationship has been established adopting a statistically reliable CoMFA model showing high prediction (r2pred=0.718, r2ncv=0.995)

Synthesis, biological evaluation and structure–activity relationship of 2-styrylquinazolones as anti-tubercular agents

2-Styrylquinazolones are reported as a novel class of potent anti-mycobacterial agents. Forty-six target compounds have been synthesized using one pot reaction involving isatoic anhydride, amine, and triethyl orthoacetate followed by aldehyde to construct the 2-styrylquinazolone scaffold. The anti-mycobacterial potency of the compounds was determined against H37Rv strain. Twenty-six compounds exhibited anti-Mtb activity in the range of 0.40–6.25 μg/mL. Three compounds 8c, 8d and 8ab showed MIC of 0.78 μg/mL and were found to be non-toxic (<50% inhibition at 50 μg/mL) to HEK 293T cell lines with the therapeutic index>64. The most potent compound 8ar showed MIC of 0.40 μg/mL with the therapeutic index>125. An early structure activity relationship for this class of compounds has been established. The computational studies indicate the possibility of these compounds binding to the penicillin binding proteins (PBPs)

N-arylalkylbenzo[d]thiazole-2-carboxamides as anti-mycobacterial agents: design, new methods of synthesis and biological evaluation

Benzothiazole-2-carboxyarylalkylamides are reported as a new class of potent anti-mycobacterial agents. Forty-one target compounds have been synthesized following a green synthetic strategy using water as the reaction medium to construct the benzothiazole scaffold followed by (i) microwave-assisted catalyst-free and (ii) ammonium chloride-catalyzed solvent-free amide coupling. The anti-mycobacterial potency of the compounds was determined against H37Rv strain. Twelve compounds exhibited promising anti-TB activity in the range of 0.78–6.25 μg mL-1 and were found to be non-toxic (<50% inhibition at 50 μg mL-1) to HEK 293T cell lines with therapeutic index (TI) of 8–64. The most promising anti-TB compound 5bf showed MIC of 0.78 μg mL-1 (TI > 64). The molecular docking studies of 5bf predict it to be a ligand for the M. tuberculosis HisG, the putative drug target for tuberculosis and could serve as a guiding principle for lead optimization

Synthesis, molecular docking and anti-mycobacterial evaluation of new imidazo1,2-a]pyridine-2-carboxamide derivatives

New anti-tubercular agents, imidazo1,2-a]pyridine-2-carboxamide derivatives (5a-q) have been designed and synthesized. The structural considerations of the designed molecules were further supported by the docking study with a long-chain enoyl-acyl carrier protein reductase (InhA). The chemical structures of the new compounds were characterized by IR, H-1 NMR, C-13 NMR, HRMS and elemental analysis. In addition, single crystal X-ray diffraction has also been recorded for compound 5f. Compounds were evaluated in vitro against Mycobacterium tuberculosis H37Rv, and cytotoxicity against HEK-293T cell line. Amongst the tested compounds 5j, 5l and 5q were emerged as good anti-tubercular agents with low cytotoxicity. The structure-anti TB activity relationship of these derivatives was explained by molecular docking. (C) 2014 Elsevier Masson SAS. All rights reserved