Design, Synthesis, and Characterization of N-Oxide-Containing Heterocycles with in Vivo Sterilizing Antitubercular Activity.

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is the infectious disease responsible for the highest number of deaths worldwide. Herein, 22 new N-oxide-containing compounds were synthesized followed by in vitro and in vivo evaluation of their antitubercular potential against Mtb. Compound 8 was found to be the most promising compound, with MIC90 values of 1.10 and 6.62 µM against active and nonreplicating Mtb, respectively. Additionally, we carried out in vivo experiments to confirm the safety and efficacy of compound 8; the compound was found to be orally bioavailable and highly effective, leading to a reduction of Mtb to undetectable levels in a mouse model of infection. Microarray-based initial studies on the mechanism of action suggest that compound 8 blocks translation. Altogether, these results indicate that benzofuroxan derivative 8 is a promising lead compound for the development of a novel chemical class of antitubercular drugs.

Synthesis and biological activity of furoxan derivatives against Mycobacterium tuberculosis.

Tuberculosis (TB) remains a serious health problem responsible to cause millions of deaths annually. The scenario becomes alarming when it is evaluated that the number of new drugs does not increase proportionally to the emergence of resistance to the current therapy. Furoxan derivatives, known as nitric oxide (NO) donors, have been described to exhibit antitubercular activity. Herein, a novel series of hybrid furoxan derivatives (1,2,5-oxadiazole 2-N-oxide) (compounds 4a-c, 8a-c and 14a-c) were designed, synthesized and evaluated in vitro against Mycobacterium tuberculosis (MTB) H37Rv (ATCC 27294) and a clinical isolate MDR-TB strain. The furoxan derivatives have exhibited MIC90 values ranging from 1.03 to 62 µM (H37Rv) and 7.0-50.0 µM (MDR-TB). For the most active compounds (8c, 14a, 14b and 14c) the selectivity index ranged from 3.78 to 52.74 (MRC-5 cells) and 1.25-34.78 (J774A.1 cells). In addition, it was characterized for those compounds logPo/w values between 2.1 and 2.9. All compounds were able to release NO at levels ranging from 0.16 to 44.23%. Among the series, the phenylsulfonyl furoxan derivatives (compounds 14a-c) were the best NO-donor with the lowest MIC90 values. The most active compound (14c) was also stable at different pHs (5.0 and 7.4). In conclusion, furoxan derivatives were identified as new promising compounds useful to treat tuberculosis.

Bioactivity of pyridine-2-thiolato-1-oxide metal complexes: Bi(III), Fe(III) and Ga(III) complexes as potent anti-Mycobacterium tuberculosis prospective agents.

In the search for new therapeutic tools against tuberculosis and to further address the therapeutic potential of pyridine-2-thiol 1-oxide (Hmpo) metal complexes, two new octahedral [M(III)(mpo)3] complexes, with M = Ga or Bi, were synthesized and characterized in the solid state and in solution. Attempts to crystallize [Ga(III)(mpo)3] in CH2Cl2 led to single crystals of the reaction product [GaCl(mpo)2], where the gallium(III) ion is in a square basis pyramidal environment, trans-coordinated at the basis to two pyridine-2-thiolato 1-oxide anions acting as bidentate ligands through their oxygen and sulfur atoms. The biological activity of the new [M(III)(mpo)3] complexes together with that of the previously reported Fe(III) analogous compound and the pyridine-2-thiol 1-oxide sodium salt (Na mpo) was evaluated on Mycobacterium tuberculosis. The compounds showed excellent activity, both in the standard strain H37Rv ATCC 27294 (pan-susceptible) and in five clinical isolates that are resistant to the standard first-line anti-tuberculosis drugs isoniazid and rifampicin. These pyridine-2-thiol 1-oxide derivatives are promising compounds for the treatment of resistant tuberculosis.

Comparison of resazurin microtiter assay performance and BACTEC MGIT 960 in the susceptibility testing of Brazilian clinical isolates of Mycobacterium tuberculosis to four first-line drugs.

We assessed the performance of REMA in comparison with BACTEC MGIT 960 in the susceptibility testing of 80 Mycobacterium tuberculosis clinical isolates from Clemente Ferreira Institute against four drugs. REMA proved to be a rapid and accurate method, providing excellent correlation with BACTEC MGIT 960, with the exception of results for the ethambutol drug.

Comparison of resazurin microtiter assay performance and BACTEC MGIT 960 in the susceptibility testing of Brazilian clinical isolates of Mycobacterium tuberculosis to four first-line drugs

We assessed the performance of REMA in comparison with BACTEC MGIT 960 in the susceptibility testing of 80 Mycobacterium tuberculosis clinical isolates from Clemente Ferreira Institute against four drugs. REMA proved to be a rapid and accurate method, providing excellent correlation with BACTEC MGIT 960, with the exception of results for the ethambutol drug.

Drug resistance in Mycobacterium tuberculosis clinical isolates from Brazil: phenotypic and genotypic methods.

We determined the susceptibility profile of 80 Mycobacterium tuberculosis (MTB) clinical isolates from Brazil against isoniazid (INH) and rifampicin (RIF) drugs by two phenotypic methods (Resazurin Microtiter Assay - REMA and BACTEC™ MGIT™ Mycobacterial Detection System). DNA polymorphisms were also determined by PCR-SSCP in isolates resistant to INH and RIF. BACTEC™ MGIT™ 960 detected 22 susceptible isolates to INH and RIF, 48 MDR isolates (resistant at least to INH and RIF) and nine mono-resistant isolates (eight to INH and one to RIF). REMA performance was determined by Receiver Operating Characteristic curve, whose assay was validated utilizing as reference the BACTEC™ MGIT™ 960 system. ROC curve showed cut-off values of 0.0625µg/mL and 0.125µg/mL, for INH and RIF, respectively. REMA-INH demonstrated sensitivity and specificity of 100% while REMA-RIF showed sensitivity of 97.2% and specificity of 100%. PCR-SSCP detected DNA polymorphisms in 87.5% and 75.5% of isolates classified as INH-resistant and RIF-resistant, respectively. One discordant sample found to RIF (resistant by BACTEC™ MGIT™ 960 and susceptible by REMA) showed no mutation by PCR-SSCP. In conclusion, our studies demonstrated that the combination of phenotypic method REMA, which allowed rapid detection of MDR-MTB with higher levels of sensitivity and specificity, with the genotypic method PCR-SSCP, which demonstrated high accuracy in the search of polymorphisms in the resistance genes, proved to be a useful strategy to study MDR-MTB clinical isolates from national reference center located in São Paulo city.