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Despite the established treatment regimens, tuberculosis remains an alarming threat to public health according to WHO. Novel agents are needed to overcome the increasing rate of resistance and perhaps achieve eradication. As part of our long-term research on pyrazine derived compounds, we prepared a series of their ortho fused derivatives, N-phenyl- and N-benzyl quinoxaline-2-carboxamides, and evaluated their in vitro antimycobacterial activity. In vitro activity against Mycobacterium tuberculosis H37Ra (represented by minimum inhibitory concentration, MIC) ranged between 3.91–500 µg/mL, with most compounds having moderate to good activities (MIC &lt, 15.625 µg/mL). The majority of the active compounds belonged to the N-benzyl group. In addition to antimycobacterial activity assessment, final compounds were screened for their in vitro cytotoxicity. N-(naphthalen-1-ylmethyl)quinoxaline-2-carboxamide (compound 29) was identified as a potential antineoplastic agent with selective cytotoxicity against hepatic (HepG2), ovarian (SK-OV-3), and prostate (PC-3) cancer cells lines. Molecular docking showed that human DNA topoisomerase and vascular endothelial growth factor receptor could be potential targets for 29.

Human cytosolic prolyl-tRNA synthetase (HcProRS) catalyses the formation of the prolyl-tRNAPro, playing an important role in protein synthesis. Inhibition of HcProRS activity has been shown to have potential benefits in the treatment of fibrosis, autoimmune diseases and cancer. Recently, potent pyrazinamide-based inhibitors were identified by a high-throughput screening (HTS) method, but no further elaboration was reported. The pyrazinamide core is a bioactive fragment found in numerous clinically validated drugs and has been subjected to various modifications. Therefore, we applied a virtual screening protocol to our in-house library of pyrazinamide-containing small molecules, searching for potential novel HcProRS inhibitors. We identified a series of 3-benzylaminopyrazine-2-carboxamide derivatives as positive hits. Five of them were confirmed by a thermal shift assay (TSA) with the best compounds 3b and 3c showing EC50 values of 3.77 and 7.34 µM, respectively, in the presence of 1 mM of proline (Pro) and 3.45 µM enzyme concentration. Co-crystal structures of HcProRS in complex with these compounds and Pro confirmed the initial docking studies and show how the Pro facilitates binding of the ligands that compete with ATP substrate. Modelling 3b into other human class II aminoacyl-tRNA synthetases (aaRSs) indicated that the subtle differences in the ATP binding site of these enzymes likely contribute to its potential selective binding of HcProRS. Taken together, this study successfully identified novel HcProRS binders from our anti-tuberculosis in-house compound library, displaying opportunities for repurposing old drug candidates for new applications such as therapeutics in HcProRS-related diseases. ispartof: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES vol:22 issue:15 ispartof: location:Switzerland status: published

We prepared a series of substituted N-(pyrazin-2-yl)benzenesulfonamides as an attempt to investigate the effect of different linkers connecting pyrazine to benzene cores on antimicrobial activity when compared to our previous compounds of amide or retro-amide linker type. Only two compounds, 4-amino-N-(pyrazin-2-yl)benzenesulfonamide (MIC = 6.25 &mu, g/mL, 25 &mu, M) and 4-amino-N-(6-chloropyrazin-2-yl)benzenesulfonamide (MIC = 6.25 &mu, g/mL, 22 &mu, M) exerted good antitubercular activity against M. tuberculosis H37Rv. However, they were excluded from the comparison as they&mdash, unlike the other compounds&mdash, possessed the pharmacophore for the inhibition of folate pathway, which was proven by docking studies. We performed target fishing, where we identified matrix metalloproteinase-8 as a promising target for our title compounds that is worth future exploration.

We prepared a series of substituted N-(pyrazin-2-yl)benzenesulfonamides as an attempt to investigate the effect of different linkers connecting pyrazine to benzene cores on antimicrobial activity when compared to our previous compounds of amide or retro-amide linker type. Only two compounds, 4-amino-N-(pyrazin-2-yl)benzenesulfonamide (MIC = 6.25 μg/mL, 25 μM) and 4-amino-N-(6-chloropyrazin-2-yl)benzenesulfonamide (MIC = 6.25 μg/mL, 22 μM) exerted good antitubercular activity against M. tuberculosis H37Rv. However, they were excluded from the comparison as they—unlike the other compounds—possessed the pharmacophore for the inhibition of folate pathway, which was proven by docking studies. We performed target fishing, where we identified matrix metalloproteinase-8 as a promising target for our title compounds that is worth future exploration.

In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy of 5-chloro-N-(2-fluorophenyl)pyrazine-2-carboxamide. Theoretical calculations were performed by using Density Functional Theory (DFT). The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution. The calculated wavenumbers were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and related properties of the molecule illustrate the reactivity of the title compound. The hyperpolarizability of the title compound was calculated and was in good agreement with similar derivatives. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization was analysed using natural bond orbital analysis. From MEP plot, it is evident that the negative charge covers the C=O group and the positive region is over the NH group. Molecular docking studies suggest that the compound might exhibit inhibitory activity against ACP reductase.

Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department: Dpt. of Pharmaceutical Chemistry and Drug Control Candidate: Mgr. Jan Zitko Supervisor: Prof. PharmDr. Martin Doležal, Ph.D. Title of Doctoral Thesis: Derivatives of pyrazinecarboxylic acid as potential antituberculotics (synthesis and biological evaluation) This thesis deals with derivatives of pyrazine-2-carboxylic (POA) acid with potential antimycobacterial activity. In the theoretical part of the thesis there is a short description of tuberculosis (TB) disease, discussion of its epidemiology an associated risk factors of increasing resistance to fist-line antituberculars and the co-infection with HIV. Antituberculars used in clinical practice are described as well as the summary of new antituberculars under clinical trials is presented. Pyrazinamide (PZA) as one of the most important first-line antituberculars is in the focus of this thesis. Multiple up-to-date theories of PZA (POA) mechanism of action are described and discussed. Importantly, a summary of structural changes of PZA/POA attempted in the past to prepare new antituberculars is presented and the importance and relevance of individual structural changes is discussed. In the practical part of this thesis, 76 derivatives of PZA/POA were prepared, 68 of...