Phenylisoxazole-3/5-Carbaldehyde Isonicotinylhydrazone Derivatives: Synthesis, Characterization, and Antitubercular Activity

Eight new phenylisoxazole isoniazid derivatives, 3-(2′-fluorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (1), 3-(2′-methoxyphenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (2), 3-(2′-chlorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (3), 3-(3′-clorophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (4), 3-(4′-bromophenyl)isoxazole-5-carbaldehyde isonicotinylhydrazone (5), 5-(4′-methoxiphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (6), 5-(4′-methylphenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (7), and 5-(4′-clorophenyl)isoxazole-3-carbaldehyde isonicotinylhydrazone (8), have been synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR, and mass spectral data. The 2D NMR (1H-1H NOESY) analysis of 1 and 2 confirmed that these compounds in acetone-d6 are in the trans(E) isomeric form. This evidence is supported by computational calculations which were performed for compounds 1–8, using DFT/B3LYP level with the 6-311++G(d,p) basis set. The in vitro antituberculous activity of all the synthesized compounds was determined against the Mycobacterium tuberculosis standard strains: sensitive H37Rv (ATCC-27294) and resistant TB DM97. All the compounds exhibited moderate bioactivity (MIC = 0.34–0.41 μM) with respect to the isoniazid drug (MIC = 0.91 μM) against the H37Rv sensitive strain. Compounds 6 (X = 4′-OCH3) and 7 (X = 4′-CH3) with MIC values of 12.41 and 13.06 μM, respectively, were about two times more cytotoxic, compared with isoniazid, against the resistant strain TB DM97.

In-silico study of antituberculous activity of Zn-pyrazinamide in pyrazinamidase

Tuberculosis is caused by Mycobacterium tuberculosis and is one of the leading causes of death. Treatment with pyrazinamide depends on the formation of the bioactive species, pyrazinoic acid (POA), catalyzed by the enzyme pyrazinamidase (PZAse). New mutant strains show resistance to PZA, therefore, it is necessary to search for new drugs. Metallodrugs can offer a synergistic effect on the biological activity of the metal and the drug. Recent studies by our group show anti-tuberculosis activity of pyrazinamide coordinated with Zn, however, the mechanism of action is unknown. In this work, an in-silico study was carried out in three stages: Quantum mechanical, molecular docking and molecular dynamics simulations. ZnPZA (Egap = 4.12 eV) presented greater chemical reactivity than PZA (Egap = 4.97 eV). Greater binding energy was found in ZnPZA-PZAse (-6.98 kcal/mol) than in PZA-PZAse (-6.48 kcal/mol). RMSD and RMSF show stability in PZA-PZAse and ZnPZA-PZAse dockings. Hydrogen bonds interaction of ZnPZA with the catalytic amino acids Asp8 and Lys96 occurs for 83 and 40 ns, respectively. It is concluded that ZnPZA could serve as a transporter of PZA to the active site of PZAse, to promote the production of POA and the antituberculous effect; however, further experimental studies are needed.

Impact of immunopathology on the antituberculous activity of pyrazinamide

In the 1970s, inclusion of pyrazinamide (PZA) in the drug regimen of tuberculosis (TB) patients for the first 2 mo achieved a drastic reduction of therapy duration. Until now, however, the mechanisms underlying PZA’s unique contribution to efficacy have remained controversial, and animal efficacy data vary across species. To understand how PZA kills bacterial populations present in critical lung lesion compartments, we first characterized a rabbit model of active TB, showing striking similarities in lesion types and fates to nonhuman primate models deemed the most appropriate surrogates of human TB. We next employed this model with lesion-centric molecular and bacteriology readouts to demonstrate that PZA exhibits potent activity against Mycobacterium tuberculosis residing in difficult-to-sterilize necrotic lesions. Our data also indicate that PZA is slow acting, suggesting that PZA administration beyond the first 2 mo may accelerate the cure. In conclusion, we provide a pharmacodynamic explanation for PZA’s treatment-shortening effect and deliver new tools to dissect the contribution of immune response versus drug at the lesion level.

Carboxylation of hydroxyarens with metal alkyl carbonates

The objective of this work was to investigate the possibility of using alkali metal salts of ethylcarbonic acid as a carboxylating reagent in phenol (naphthols) carboxylation and developing a new and simple method for the synthesis of hydroxybenzoic and hydroxynaphthoic acids having broad practical application. It was found that sodium ethyl carbonate and potassium ethyl carbonate can be successfully used as carboxylating agents in carboxylation of phenol and naphthols. For the first time, the effects of the gaseous medium (air, carbon dioxide, argon), pressure, temperature and reaction time on the proceedings of the carboxylation reactions were examined. Simple and convenient procedures for the syntheses of o- and p-hydroxybenzoic, p-aminosalicylic, 1-hydroxy-2-naphthoic, 1-hydroxy-4-naphthoic and 2-hydroxy-3-naphthoic acids were developed. New efficient technologies for preparation of drugs salicylic acid (antiseptic activity), p-aminosalicylic acid (antituberculous activity) and p-hydroxybenzoic acid (bactericide activity) based on carboxylation reactions of phenol and m-aminophenol with sodium and potassium salts of ethyl carbonic acid were worked out.