Design of hybrid molecules as antimycobacterial compounds: Synthesis of isoniazid-naphthoquinone derivatives and their activity against susceptible and resistant strains of Mycobacterium tuberculosis.

Isoniazid-naphthoquinone hybrids were synthesized and evaluated against a susceptible (H37Rv) strain and two isoniazid-resistant strains (INHR1 and INHR2) of Mycobacterium tuberculosis. The antimycobacterial activity of the derivatives was determined based on the resazurin microtiter assay and their cytotoxicity in adhered mouse monocyte macrophage J774.A1 cells (ATCC TIB-67). Of the twenty-two compounds evaluated against the three strains of M. tuberculosis, twenty-one presented some activity against the H37Rv and INHR1 (katG S315T) or INHR2 (inhA C(-5)T) strains. Compounds 1a, 2a, and 8a were effective against the INHR1 strain, and compounds 1a, 1b, 2a, 3a, 5a, 5b and 8a were effective against the INHR2 strain, with MICs in the range of 3.12-6.25 µg/mL. Compounds 1b and 5b were the most active against H37Rv, with MIC of 0.78 µg/mL. Based on the selectivity index, 1b and 5b can be considered safe as a drug candidate compounds. These results demonstrate that quinoidal compounds can be used as promising scaffolds for the development of new anti-TB drugs and hybrids with activity against M. tuberculosis-susceptible and INH-resistant strains.

Naphthoquinone Derivatives as Scaffold to Develop New Drugs for Tuberculosis Treatment.

Despite being a curable disease, tuberculosis (TB) remains a public health problem worldwide mainly due to lengthy treatment, as well as its toxic effects, TB/HIV co-infection and the emergence of resistant Mycobacterium tuberculosis strains. These barriers reinforcing the need for development of new antimicrobial agents, that ideally should reduce the time of treatment and be active against susceptible and resistant strains. Quinones are compounds found in natural sources and among them, the naphthoquinones show antifungal, antiparasitic, and antimycobacterial activity. Thus, we evaluated the potential antimycobacterial activity of six 1,4-naphthoquinones derivatives. We determined the minimum inhibitory concentration (MIC) of the compounds against three M. tuberculosis strains: a pan-susceptible H37Rv (ATCC 27294); one mono-resistant to isoniazid (ATCC 35822); and one mono-resistant to rifampicin (ATCC 35838); the cytotoxicity in the J774A.1 (ATCC TIB-67) macrophage lineage; performed in silico analysis about absorption, distribution, metabolism, and excretion (ADME) and docking sites. All evaluated naphthoquinones were active against the three strains with MIC between 206.6 and 12.5 µM, and the compounds with lower MIC values have also showed low cytotoxicity. Moreover, two naphthoquinones derivatives 5 and 6 probably do not exhibit cross resistance with isoniazid and rifampicin, respectively, and regarding ADME analysis, no compound violated the Lipinski's rule-of-five. Considering the set of findings in this study, we conclude that these naphthoquinones could be promising scaffolds to develop new therapeutic strategies to TB.

Activity of Rifabutin and Hemi-synthetic Derivatives Against Mycobacterium abscessus.

BACKGROUND: Mycobacterium abscessus causes a wide range of clinical diseases that are difficult to treat. This microorganism is resistant not only to the classical antituberculosis agents but also to most of the antimicrobials that are currently available, resulting in limited therapeutic options and treatment failure. This scenario stresses the need to search for new drugs with activity against M. abscessus. OBJECTIVE: To evaluate in vitro the antimycobacterial activity and cytotoxicity of rifabutin (RFB 1) and ten derivatives (2-11) against M. abscessus ATCC 19977. METHOD: The minimum inhibitory concentration (MIC) of the molecules was determined by the microdilution broth method according to the guideline described in CLSI. The toxicity evaluation was carried in 96-well microplates, using the cell line J774A.1 (ATCC TIB-67). RESULT: From the eleven molecules tested, RFB 1 and RFB 4 were the compounds showing higher activities against M. abscessus, with MICs of 0.9 and 1.0 µM, respectively. The R1 and R2 moieties seem to have deciding influence over the final activity. Furthermore, N-oxide derivatives 9, 10, and 11 were also active against M. abscessus, with MICs of 7.2 µM, 1.8 µM and 3.8 µM, respectively. An explanatory hypothesis for the better activities of compounds RFB 1, RFB 4, RFB 10 and RFB 11 considers the likely hydrogen bonding between ligands and receptor, balancing the global flexibility and interaction energies. RFB 1 and its most effective derivatives were found to be not toxic. CONCLUSION: Besides RFB 1, its derivatives 4, 10 and 11 show potential for clinical development in the M. abscessus treatment.