Věra Klimešová

Heterocyclic benzazole derivatives with antimycobacterial in vitro activity.

The series of 2-benzylsulfanyl derivatives of benzoxazole and benzothiazole were synthesized, evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis and non-tuberculous mycobacteria, and the activity expressed as the minimum inhibitory concentration (MIC) in micromol/L. The substances bearing two nitro groups (4e, 4f, 5e, 5f) or a thioamide group (4i, 4j, 5i, 5j) exhibited appreciable activity particularly against non-tuberculous strains. The most active compounds were subjected to the toxicity assay and were evaluated as moderately cytotoxic.

Influence of the replacement of the oxo function with the thioxo group on the antimycobacterial activity of 3-aryl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones.

Series of 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithiones, 3-arylquinazoline-2,4(1H,3H)-diones and 3-arylquinazoline-2,4(1H,3H)-dithiones were synthesized, and the antimycobacterial activities of the derivatives evaluated in vitro. The compounds were active against Mycobacterium tuberculosis and conditionally pathogenic mycobacteria (Mycobacterium kansasii and Mycobacterium avium). The replacement of oxygen by sulfur in 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2.4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones gave rise to an increase of antimycobacterial activity. The most active compound was 3-(3-chlorophenyl)-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithione.

New benzimidazole derivatives as antimycobacterial agents

A set of 2-alkylsulfanyl derivatives of 5-methylbenzimidazole was synthesized and evaluated for antimycobacterial activity. The structures of the compounds were confirmed by 1H NMR and IR data, and their purity by elemental analysis. Antimycobacterial activities against Mycobacterium tuberculosis and nontuberculous mycobacteria were expressed as the minimum inhibitory concentration. The substances exhibited significant antimycobacterial activity, in particular against both strains of Mycobacterium kansasii. The effect of the most active compound in the set, 3,5-dinitro derivative 3t, exceeded that of the standard isoniazide against M. kansasii and Mycobacterium avium.

New pyridine derivatives as potential antimicrobial agents.

A set of pyridine derivatives bearing a substituted alkylthio chain or a piperidyl ring in position 2 or 4 were synthesized, and their antimycobacterial and antifugal activities were evaluated. Chemical structures were confirmed by IR and NMR data, and by elemental analysis. Minimum inhibitory concentrations (MIC) were used for the evaluation of microbiological activity in vitro. The compounds were moderately active against both Mycobacterium tuberculosis and nontuberculous mycobacteria. The most active compound was 2-cyanomethylthiopyridine-4-carbonitrile (7) with MIC against Mycobacterium kansasii in the range of 8-4 mumol/l. The antifungal activities of the compounds were relatively low.

Preparation and in vitro evaluation of benzylsulfanyl benzoxazole derivatives as potential antituberculosis agents.

A set of 2-benzylsulfanyl derivatives of benzoxazole was synthesized and evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis, non-tuberculous mycobacteria and multidrug-resistant M. tuberculosis. The activities were expressed as the minimum inhibitory concentration (MIC) in mmol/L. The substances showed similar activity against all tested strains. The lead compounds in the set, dinitro derivatives exhibited significant activity against both sensitive and resistant strains of M. tuberculosis and also against non-tuberculous mycobacteria. To facilitate drug design of benzoxazole as potential antituberculosis agent, we have explored the quantitative structure-activity relationship (QSAR). We demonstrated that lower lipophilicity has significant contribution to activity. Dinitrobenzylsulfanyl derivative of benzoxazole represents the promising small-molecule synthetic antimycobacterials.

SYNTHESIS OF 2-BENZYLTHIOPYRIDINE-4-CARBOTHIOAMIDE DERIVATIVES AND THEIR ANTIMYCOBACTERIAL, ANTIFUNGAL AND PHOTOSYNTHESIS-INHIBITING ACTIVITY

Abstract Aseries of 2-benzylthiopyridine-4-carbonitriles 4 and a series of 2-benzylthiopyridine-4-carbothioamides 5 were prepared. Their chemical structures were proved by IR and 1H NMR data and by elemental analysis. The MIC assessment was used for the estimation of their potential antimycobacterial and antifungal activity in vitro. The compounds were shown to be more active against mycobacterial strains than the tested fungi. Their antimycobacterial activity appears to be related mainly to the benzylthio moiety, while the antifungal activity appears to be related to the carbothioamide group. Substituents on the benzylthio moiety of derivatives 5 modified antifungal activity, whereas they did not play any significant role in antimycobacterial activity. The inhibiting effect of 4 and 5 on the photochemical activity of spinach chloroplasts was determined by IC50 values. The compounds exhibited a moderate photosynthesis-inhibiting activity.

1-Substituted-5-[(3,5-dinitrobenzyl)sulfanyl]-1H-tetrazoles and their isosteric analogs: A new class of selective antitubercular agents active against drug-susceptible and multidrug-resistant mycobacteria

In this work, a new class of highly potent antituberculosis agents, 1-substituted-5-[(3,5-dinitrobenzyl)sulfanyl]-1H-tetrazoles and their oxa and selanyl analogs, is described. The minimal inhibitory concentration (MIC) values reached 1 μM (0.36-0.44 μg/mL) against Mycobacterium tuberculosis CNCTC My 331/88 and 0.25-1 μM against six multidrug-resistant clinically isolated strains of M. tuberculosis. The antimycobacterial effects of these compounds were highly specific because they were ineffective against all eight bacterial strains and eight fungal strains studied. Furthermore, these compounds exhibited low in vitro toxicity in four mammalian cell lines (IC50 > 30 μM). We also examined the structure-activity relationships of the compounds, particularly the effects on antimycobacterial activity of the number and position of the nitro groups, the linker between tetrazole and benzyl moieties, and the tetrazole itself. Relatively high variability of substituent R(1) on the tetrazole in the absence of negative effects on antimycobacterial activity allows further structural optimization with respect to toxicity and the ADME properties of the 1-substituted-5-[(3,5-dinitrobenzyl)sulfanyl]-1H-tetrazoles lead compounds.

Development of 3,5-Dinitrobenzylsulfanyl-1,3,4-oxadiazoles and Thiadiazoles as Selective Antitubercular Agents Active Against Replicating and Nonreplicating Mycobacterium tuberculosis

Herein, we report the discovery and structure-activity relationships of 5-substituted-2-[(3,5-dinitrobenzyl)sulfanyl]-1,3,4-oxadiazoles and 1,3,4-thiadiazoles as a new class of antituberculosis agents. The majority of these compounds exhibited outstanding in vitro activity against Mycobacterium tuberculosis CNCTC My 331/88 and six multidrug-resistant clinically isolated strains of M. tuberculosis, with minimum inhibitory concentration values as low as 0.03 μM (0.011-0.026 μg/mL). The investigated compounds had a highly selective antimycobacterial effect because they showed no activity against the other bacteria or fungi tested in this study. Furthermore, the investigated compounds exhibited low in vitro toxicities in four proliferating mammalian cell lines and in isolated primary human hepatocytes. Several in vitro genotoxicity assays indicated that the selected compounds have no mutagenic activity. The oxadiazole and thiadiazole derivatives with the most favorable activity/toxicity profiles also showed potency comparable to that of rifampicin against the nonreplicating streptomycin-starved M. tuberculosis 18b-Lux strain, and therefore, these derivatives, are of particular interest.

Tetrazole regioisomers in the development of nitro group-containing antitubercular agents

Tetrazole derivatives containing nitro substituents have been identified as promising antitubercular agents. In this study, the antitubercular potency, selectivity and toxicity of tetrazole 1,5- and 2,5-regioisomers were examined. We prepared a series of 1- and 2-alkyl-5-benzylsulfanyl-2H-tetrazoles and their selenium analogs with various nitro group substitutions. These 1,5- and 2,5-regioisomers were isolated and unambiguously identified using 1H and/or 13C NMR. Among the prepared compounds, 1- and 2-alkyl-5-[(3,5-dinitrobenzyl)sulfanyl]-2H-tetrazole derivatives and their selenium bioisosteres showed the highest antimycobacterial activity, with minimal inhibitory concentration (MIC) values of approximately 1 μM (0.37–0.46 μg mL−1) against Mycobacterium tuberculosis CNCTC My 331/88. The 2-alkyl regioisomers exhibited consistently higher antimycobacterial activity and lower in vitro toxicity against a mammalian cell line compared to the 1-alkyl isomers. The antimycobacterial activity of the 2-alkyl regioisomers was less influenced by the type of alkyl substituent in contrast to 1-alkyl isomers. Furthermore, the 3,5-dinitrobenzyl moiety per se is not the carrier of mutagenicity. These findings encourage further optimization of the 2-alkyl chain to improve the pharmacokinetic properties and toxicity of 2-alkyl-5-[(3,5-dinitrobenzyl)sulfanyl]-2H-tetrazole lead compounds.

Combination of molecular modeling and quantitative structure-activity relationship analysis in the study of antimycobacterial activity of pyridine derivatives

A set of 4-benzylsulfanyl derivatives of pyridine-2-carbonitriles and pyridine-2-carbothioamides, previously tested for their antimycobacterial activity, were analysed by quantitative structure-activity relationship (QSAR) techniques, using some physicochemical and quantum-chemical parameters. The resulting QSAR revealed that the activity increases with electron withdrawing substituents in the benzyl moiety of studied compounds. HOMO orbitals can play an important role in the description of the mechanism of interactions at the molecular level. Additionally, the results of multiple linear regression indicate the differences between Mycobacterium tuberculosis and M. avium. The hydrophobicity of studied compounds is important for activity against M. avium.