novobiocin and Tuberculosis

An efficient three-component, one-pot protocol is described for the synthesis of biologically interesting 2-(benzylideneamino)-N-(7-chloroquinolin-4-yl)benzohydrazide derivatives from isatoic anhydride, 7-chloro-4-hydrazinylquinoline and aromatic and/or hetero aromatic aldehydes under catalyst free condensation by using water as reaction media. All synthesized compounds were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis (MTB) and cytotoxicity activity against normal VERO cell lines. The synthesized compounds exhibited minimum inhibitory concentration (MIC) ranging from 0.78 to 25μM. Among the tested compounds 4c, 4o, 4r, and 4u exhibited promising inhibitory activity (MIC=3.12μM). Compounds 4h and 4i stand out, showing MIC values of 0.78 and 1.56μM respectively. Both compounds were further screened for their Mycobacterium tuberculosis DNA gyrase inhibitory assay which suggested that these compounds have a great potential for further optimization and development as antitubercular agents.

Topics: Aminoquinolines; Animals; Antitubercular Agents; DNA Gyrase; Humans; Microbial Sensitivity Tests; Mycobacterium tuberculosis; ortho-Aminobenzoates; Schiff Bases; Structure-Activity Relationship; Topoisomerase II Inhibitors; Tuberculosis; Vero Cells

Topoisomerases are an important class of enzymes for regulating the DNA transaction processes. Mycobacterium tuberculosis (Mtb) is one of the most formidable pathogens also posing serious challenges for therapeutic interventions. The organism contains only one type IA topoisomerase (Rv3646c), offering an opportunity to test its potential as a candidate drug target. To validate the essentiality of M. tuberculosis topoisomerase I (TopoI(Mt) ) for bacterial growth and survival, we have generated a conditionally regulated strain of topoI in Mtb. The conditional knockdown mutant exhibited delayed growth on agar plate. In liquid culture, the growth was drastically impaired when TopoI expression was suppressed. Additionally, novobiocin and isoniazid showed enhanced inhibitory potential against the conditional mutant. Analysis of the nucleoid revealed its altered architecture upon TopoI depletion. These studies establish the essentiality of TopoI for the M. tuberculosis growth and open up new avenues for targeting the enzyme.

Topics: Anti-Bacterial Agents; Bacterial Proteins; DNA Topoisomerases, Type I; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Gene Knockdown Techniques; Genes, Essential; Humans; Isoniazid; Microbial Sensitivity Tests; Microbial Viability; Mutation; Mycobacterium tuberculosis; Novobiocin; Oxazines; Tetracyclines; Tuberculosis; Xanthenes

Tuberculosis and other bacterial diseases represent a significant threat to human health. The DNA topoisomerases are excellent targets for chemotherapy, and DNA gyrase in particular is a well-validated target for antibacterial agents. Naphthoquinones (e.g. diospyrin and 7-methyljuglone) have been shown to have therapeutic potential, particularly against Mycobacterium tuberculosis. We have found that these compounds are inhibitors of the supercoiling reaction catalyzed by M. tuberculosis gyrase and other gyrases. Our evidence strongly suggests that the compounds bind to the N-terminal domain of GyrB, which contains the ATPase active site, but are not competitive inhibitors of the ATPase reaction. We propose that naphthoquinones bind to GyrB at a novel site close to the ATPase site. This novel mode of action could be exploited to develop new antibacterial agents.

Topics: Adenosine Triphosphate; Anti-Infective Agents; Binding Sites; Catalytic Domain; DNA; DNA Gyrase; Escherichia coli; Humans; Inhibitory Concentration 50; Mass Spectrometry; Models, Chemical; Mycobacterium tuberculosis; Naphthoquinones; Protein Binding; Protein Structure, Tertiary; Staphylococcus aureus; Surface Plasmon Resonance; Tuberculosis

Topics: Anti-Bacterial Agents; Antibiotics, Antitubercular; Humans; In Vitro Techniques; Mycobacterium tuberculosis; Novobiocin; Tuberculosis