We report the design, synthesis, and in vitro antimicrobial activity of a series of N-substituted 3-aminopyrazine-2-carboxamides with free amino groups in position 3 on the pyrazine ring. Based on various substituents on the carboxamidic moiety, the series is subdivided into benzyl, alkyl, and phenyl derivatives. The three-dimensional structures of the title compounds were predicted using energy minimization and low mode molecular dynamics under AMBER10:EHT forcefield. Compounds were evaluated for antimycobacterial, antibacterial, and antifungal activities in vitro. The most active compound against Mycobacterium tuberculosis H37Rv (Mtb) was 3-amino-N-(2,4-dimethoxyphenyl)pyrazine-2-carboxamide (17, MIC = 12.5 µg/mL, 46 µM). Antimycobacterial activity against Mtb and M. kansasii along with antibacterial activity increased among the alkyl derivatives with increasing the length of carbon side chain. Antibacterial activity was observed for phenyl and alkyl derivatives, but not for benzyl derivatives. Antifungal activity was observed in all structural subtypes, mainly against Trichophyton interdigitale and Candida albicans. The four most active compounds (compounds 10, 16, 17, 20) were evaluated for their in vitro cytotoxicity in HepG2 cancer cell line; only compound 20 was found to exert some level of cytotoxicity. Compounds belonging to the current series were compared to previously published, structurally related compounds in terms of antimicrobial activity to draw structure activity relationships conclusions.

• Keywords
• aminopyrazine, antibacterial activity, antifungal activity, antimycobacterial activity, cytotoxicity, pyrazinamide derivatives,
• MeSH
• Anti-Bacterial Agents chemical synthesis   chemistry   pharmacology   MeSH
• Antifungal Agents pharmacology   MeSH
• Bacteria drug effects   MeSH
• Cell Death drug effects   MeSH
• Hep G2 Cells MeSH
• Fungi drug effects   MeSH
• Humans MeSH
• Microbial Sensitivity Tests MeSH
• Molecular Conformation MeSH
• Pyrazines chemical synthesis   chemistry   pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Antifungal Agents MeSH
• Pyrazines MeSH

Hybrid compounds based on a combination of the first-line antitubercular pyrazinamide (PZA) and a formerly identified antimycobacterial scaffold of 4-arylthiazol-2-amine were designed. Eighteen compounds were prepared, characterized and tested for in vitro growth inhibition activity against M. tuberculosis H37Rv, M. kansasii, M. avium and M. smegmatis by Microplate Alamar Blue Assay at neutral pH. Active compounds were tested for in vitro cytotoxicity in the human hepatocellular carcinoma cell line (HepG2). The most active 6-chloro-N-[4-(4-fluorophenyl)thiazol-2-yl]pyrazine-2-carboxamide (9b) also had the broadest spectrum of activity and inhibited M. tuberculosis, M. kansasii, and M. avium with MIC = 0.78 μg mL-1 (2.3 μM) and a selectivity index related to HepG2 cells of SI > 20. Structure-activity relationships within the series are discussed. Based on its structural similarity to known inhibitors and the results of a molecular docking study, we suggest mycobacterial beta-ketoacyl-(acyl-carrier-protein) synthase III (FabH) as a potential target.

• Publication type
• Journal Article MeSH

The 46th EuroCongress on Drug Synthesis and Analysis (ECDSA-2017) was arranged within the celebration of the 65th Anniversary of the Faculty of Pharmacy at Comenius University in Bratislava, Slovakia from 5-8 September 2017 to get together specialists in medicinal chemistry, organic synthesis, pharmaceutical analysis, screening of bioactive compounds, pharmacology and drug formulations; promote the exchange of scientific results, methods and ideas; and encourage cooperation between researchers from all over the world. The topic of the conference, "Drug Synthesis and Analysis," meant that the symposium welcomed all pharmacists and/or researchers (chemists, analysts, biologists) and students interested in scientific work dealing with investigations of biologically active compounds as potential drugs. The authors of this manuscript were plenary speakers and other participants of the symposium and members of their research teams. The following summary highlights the major points/topics of the meeting.

• Keywords
• chemical biology, drug design and development, medicinal chemistry, natural compounds, new small entities, organic synthesis, pharmaceutical analysis, therapeutic proteins,
• MeSH
• Pharmacists MeSH
• Chemistry, Pharmaceutical MeSH
• Quantitative Structure-Activity Relationship MeSH
• Humans MeSH
• Intersectoral Collaboration MeSH
• Drug Compounding * MeSH
• Research Personnel MeSH
• Check Tag
• Humans MeSH
• Publication type
• Congress MeSH
• Geographicals
• Slovakia MeSH

Aminodehalogenation of 3-chloropyrazine-2-carboxamide with variously substituted benzylamines yielded a series of fifteen 3-benzylaminopyrazine-2-carboxamides. Four compounds possessed in vitro whole cell activity against Mycobacterium tuberculosis H37Rv that was at least equivalent to that of the standard pyrazinamide. MIC values ranged from 6 to 42 μM. The best MIC (6 μM) was displayed by 3-[(4-methylbenzyl)amino]pyrazine-2-carboxamide (8) that also showed low cytotoxicity in the HepG2 cell line (IC50 ≥ 250 μM). Only moderate activity against Enterococcus faecalis and Staphylococcus aureus was observed. No activity was detected against any of tested fungal strains. Molecular docking with mycobacterial enoyl-ACP reductase (InhA) was performed to investigate the possible target of the prepared compounds. Active compounds shared common binding interactions of known InhAinhibitors. Antimycobacterial activity of the title compounds was compared to the previously published benzylamino-substituted pyrazines with differing substitution on the pyrazine core (carbonitrile moiety). The title series possessed comparable activity and lower cytotoxicity than molecules containing a carbonitrile group on the pyrazine ring.

• Keywords
• antibacterials, antifungals, benzylamines, cytotoxicity, microwave-assisted, pyrazinamide, tuberculosis,
• MeSH
• Amides chemistry   MeSH
• Anti-Bacterial Agents chemical synthesis   pharmacology   MeSH
• Antifungal Agents chemical synthesis   pharmacology   MeSH
• Anti-Infective Agents chemical synthesis   pharmacology   MeSH
• Antitubercular Agents chemical synthesis   pharmacology   MeSH
• Humans MeSH
• Microbial Sensitivity Tests MeSH
• Molecular Structure MeSH
• Pyrazinamide chemical synthesis   pharmacology   MeSH
• Pyrazines chemistry   MeSH
• Molecular Docking Simulation MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Amides MeSH
• Anti-Bacterial Agents MeSH
• Antifungal Agents MeSH
• Anti-Infective Agents MeSH
• Antitubercular Agents MeSH
• Pyrazinamide MeSH
• Pyrazines MeSH

A series of N-alkyl-3-(alkylamino)pyrazine-2-carboxamides and their N-alkyl-3-chloropyrazine-2-carboxamide precursors were prepared. All compounds were characterized by analytical methods and tested for antimicrobial and antiviral activity. The antimycobacterial MIC values against Mycobacterium tuberculosis H37Rv of the most effective compounds, 3-(hexylamino)-, 3-(heptylamino)- and 3-(octylamino)-N-methyl-pyrazine-2-carboxamides 14‒16, was 25 μg/mL. The compounds inhibited photosystem 2 photosynthetic electron transport (PET) in spinach chloroplasts. This activity was strongly connected with the lipophilicity of the compounds. For effective PET inhibition longer alkyl chains in the 3-(alkylamino) substituent in the N-alkyl-3-(alkylamino)pyrazine-2-carboxamide molecule were more favourable than two shorter alkyl chains.

• Keywords
• alkylation, aminodehalogenation, antimycobacterial activity, inhibition of photosynthetic electron transport, pyrazinamide, pyrazine, structure-activity relationships,
• MeSH
• Antitubercular Agents chemical synthesis   pharmacology   MeSH
• Bacterial Proteins antagonists & inhibitors   metabolism   MeSH
• Chloroplasts metabolism   MeSH
• Microbial Sensitivity Tests MeSH
• Mycobacterium tuberculosis drug effects   metabolism   MeSH
• Pyrazinamide chemical synthesis   chemistry   pharmacology   MeSH
• Pyrazines chemical synthesis   pharmacology   MeSH
• Spinacia oleracea metabolism   MeSH
• Fatty Acid Synthases antagonists & inhibitors   metabolism   MeSH
• Electron Transport drug effects   MeSH
• Structure-Activity Relationship MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antitubercular Agents MeSH
• Bacterial Proteins MeSH
• fatty acid synthase I, mycobacteria MeSH Browser
• Pyrazinamide MeSH
• Pyrazines MeSH
• Fatty Acid Synthases MeSH