Determination of anti-tuberculosis activity of biosynthesized gold nanocompounds against M. tuberculosis H37RV.

BACKGROUND: The biosynthesis of gold nanoparticles using medicinal plants as reducing and stabilizing agent for synthesis is an emerging area of research due to their cost effectiveness and further diversified applications in various fields. People with HIV are prone to these opportunistic infections like TB due to the immunocompromised condition. In the present study, the nanoparticles and nanoconjugates were screened for effective anti-mycobacterial efficiency against opportunistic infections. METHODS: Incidentally, the nanoparticles were biosynthesized using single plant extract. The biosynthesized nanoparticles were initially screened for effective anti-tuberculosis activity against Mycobacterium tuberculosis. Based on the effective antimicrobial activity, a nanoconjugate was biosynthesized combining three plant extracts for a cumulative activity. RESULTS: The biosynthesized gold nanoparticles and nanoconjugates showed MIC demonstrating for 99% inhibition and MIC99 was found to be 6.42 µg/ml. Among all the 15 nanoparticles tested, seven NPs showed exceptional anti-TB activities NP1, NP2, NP6, NP7, NP10, NP12 and NP15 and the other nanoparticles exhibited varying degrees of inhibition - anti-TB activities. In the 12 nanoconjugate tested, seven nanoconjugate demonstrated exceptional anti-TB activities such as NCC1, NCC2, NCC5, NCC6, NCV1, NCV6 and NCV4. CONCLUSION: The objective of the study was to identify the nanoparticles and nanoconjugates which demonstrated potential activity against M. tuberculosis so that a single nanoparticle or nanoconjugate can be targeted to treat patients with TB. Minimum Inhibitory Concentration (MIC) of the biosynthesized gold nanoparticles and nanoconjugates were determined against M. tuberculosis H37Rv.

Myoinositol and methyl stearate increases rifampicin susceptibility among drug-resistant Mycobacterium tuberculosis expressing Rv1819c.

The alarming increase in multidrug resistance, which includes Bedaquiline and Delamanid, stumbles success in Tuberculosis treatment outcome. Mycobacterium tuberculosis gains resistance to rifampicin, which is one of the less toxic and potent anti-TB drugs, through genetic mutations predominantly besides efflux pump mediated drug resistance. In recent decades, scientific interventions are being carried out to overcome this hurdle using novel approaches to save this drug by combining it with other drugs/molecules or by use of high dose rifampicin. This study reports five small molecules namely Ellagic acid, Methyl Stearate, Myoinositol, Rutin, and Shikimic acid that exhibit synergistic inhibitory activity with rifampicin against resistant TB isolates. In-silico examinations revealed possible blocking of Rv1819c-an ABC transporter efflux pump that was known to confer resistance in M. tuberculosis to rifampicin. The synergistic anti-TB activity was assessed using a drug combination checkerboard assay. Efflux pump inhibition activity of ellagic acid, myoinositol, and methyl stearate was observed through ethidium bromide accumulation assay in the drug-resistant M. tuberculosis clinical strains and recombinant Mycobacterium smegmatis expressing Rv1819c in coherence with the significant reduction in the minimum inhibitory concentration of rifampicin. Cytotoxicity of the active efflux inhibitors was tested using in silico and ex vivo methods. Myoinositol and methyl stearate were completely non-toxic to the hematological and epithelial cells of different organs under ex vivo conditions. Based on these findings, these molecules can be considered for adjunct TB therapy; however, their impact on other drugs of anti-TB regimen needs to be tested.

A multi-targeting pre-clinical candidate against drug-resistant tuberculosis.

FNDR-20081 [4-{4-[5-(4-Isopropyl-phenyl)- [1,2,4]oxadiazol-3-ylmethyl]-piperazin-1-yl}-7-pyridin-3-yl-quinoline] is a novel, first in class anti-tubercular pre-clinical candidate against sensitive and drug-resistant Mycobacterium tuberculosis (Mtb). In-vitro combination studies of FNDR-20081 with first- and second-line drugs exhibited no antagonism, suggesting its compatibility for developing new combination-regimens. FNDR-20081, which is non-toxic with no CYP3A4 liability, demonstrated exposure-dependent killing of replicating-Mtb, as well as the non-replicating-Mtb, and efficacy in a mouse model of infection. Whole genome sequencing (WGS) of FNDR-20081 resistant mutants revealed the identification of pleotropic targets: marR (Rv0678), a regulator of MmpL5, a transporter/efflux pump mechanism for drug resistance; and Rv3683, a putative metalloprotease potentially involved in peptidoglycan biosynthesis. In summary, FNDR-20081 is a promising first in class compound with the potential to form a new combination regimen for MDR-TB treatment.

Inhibition of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase from Mycobacterium tuberculosis: in silico screening and in vitro validation.

Tuberculosis, caused by Mycobacterium tuberculosis, remains a serious global health threat, highlighting the urgent need for novel antituberculosis drugs. The shikimate pathway, responsible for aromatic amino acid biosynthesis, is required for the growth of Mycobacterium tuberculosis and is a potential drug target. 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (mtDAH7Ps) catalyzes the first step in shikimate pathway. E-pharmacophore models for inhibitors of mtDAH7Ps - tyrosine, phenylalanine, phosphoenolpyruvate and (2S)-2,7-bis(phosphonooxy)heptanoic acid were screened against ZINC synthetic and natural compounds databases. The shortlisted compounds were subjected to induce fit docking and validated by Prime/Molecular Mechanics Generalized Born Surface Area calculation to predict ligand binding energy and ligand strain energy for ligand and receptor. The lead compounds were screened for their inhibitory activity against purified mtDAH7Ps enzyme. Lead compounds inhibited mtDAH7Ps in a concentration-dependent manner; with an IC50 value of 21 µM, 42 µM and 54 µM for α-Tocopherol, rutin and 3-Pyridine carboxyaldehyde respectively. Molecular Dynamics analysis for 50 ns of the active compounds-mtDAH7Ps complexes showed that the backbone of mtDAH7Ps was stable. These results suggest that α-tocopherol, 3 - Pyridine carboxyaldehyde and rutin could be novel drug leads to inhibit mtDAH7Ps in M. tuberculosis.