Inhibitors Of Mycobacterium Tuberculosis Research Articles

MycPermCheck: the Mycobacterium tuberculosispermeability prediction tool for small molecules

With over 8 million new cases in 2010, particularly documented in developing countries, tuberculosis (TB) is still a highly present pandemic and often terminal [1]. This is also due to the emergence of antibiotic-resistant strains (MDR-TB and XDR-TB) of the primary causative agent Mycobacterium tuberculosis (MTB). Efforts to develop new effective drugs against MTB are restrained by the unique and largely impermeable mycobacterial cell wall [2]. Accordingly, tools for estimating the ability of chemical compounds to pass this barrier would significantly support TB drug discovery. Using the CDD TB database of antimycobacterial substances [3], 3,815 active and, thus, permeable compounds could be retrieved. A data mining approach was conducted to gather the similarities of these substances in terms of physico-chemical descriptors and to delimit them from a generic dataset of drug-like molecules. Principal component analyses were performed and a logistic regression model was generated on the basis of the differences of these datasets in the first principal component. This regression model was thoroughly evaluated using highly active MTB inhibitors absent in the training dataset, as well as inhibitors of the validated MTB drug target InhA. Based on these validation results, its performance is expected to be of high practical value for virtual screening purposes. The regression model was implemented into the online tool MycPermCheck to predict the permeability probability of small organic compounds against the MTB cell wall. Given the current lack of precise molecular criteria determining mycobacterial permeability, MycPermCheck represents an unprecedented knowledge-driven prediction tool intended to support antimycobacterial drug discovery. It can be used intuitively as an additional selection criterion for potential new inhibitors against MTB. The MycPermCheck online tool is freely accessible under the URL: http://www.mycpermcheck.aksotriffer.pharmazie.uni-wuerzburg.de.

Production of 3-nitropropionic acid by endophytic fungus Phomopsis longicolla isolated from Trichilia elegans A. JUSS ssp. elegans and evaluation of biological activity

The compound 3-nitropropionic acid is a potent neurotoxic agent in animals and well-known as a potent inhibitor of Mycobacterium tuberculosis. In this research, we were able to extract this compound from the endophytic fungus, Phomopsis longicolla (FJ62759), isolated from Trichilia elegans A. JUSS ssp. elegans. The aim of this study was the isolation of secondary metabolites produced by P. longicolla, the chemical identification of these compounds and evaluation of their antimicrobial and insecticidal activity. To accomplish these goals, the fungus was cultured in BD broth for 25 days without agitation at 28 °C, and then the broth was separated from the mycelium. The supernatant was partitioned with dichloromethane (CH2Cl2), ethyl acetate (EtOAc), and butanol (BuOH) solvents resulting in 3 extracts. However, only the EtOAc extract was used for fractionation and chemical identification because it had the greatest mass. After common chromatographic procedures, the fractions were analyzed by nuclear magnetic resonance to elucidate the chemical components. This procedure resulted in the identification of 3-nitropropionic acid in the D fraction. Evaluation of the insecticidal and antimicrobial activity of this compound has been accomplished, and the results indicate good inhibition of the citrus pathogen Guignardia citricarpa and cocoa pathogen Moniliophthora perniciosa and slight inhibition of the human bacterial pathogens Micrococcus luteus, Salmonella typhi and slight inhibition of phytopathogenic bacteria Xanthomonas axonopodis pv. phaseoli. The evaluation of insecticide activity did not show mortality of the Diatraea saccharalis larvae by the metabolite 3-nitropropionic acid in the D fraction. The results suggest that P. longicolla is a bioactive metabolic producing endophytic fungus with biotechnological properties.

Modelling human granuloma to study the mechanisms by which isoniazid inhibits Mycobacterium tuberculosis growth.

Frontiers Events is a rapidly growing calendar management system dedicated to the scheduling of academic events. This includes announcements and invitations, participant listings and search functionality, abstract handling and publication, related events and post-event exchanges. Whether an organizer or participant, make your event a Frontiers Event!

Phyllocladane diterpenes from Anisomeles heyneana

New phyllocladane diterpene, phyllocladan-16α,17-dihydroxy-19-oic acid (1), together with known phyllocladane diterpene, phyllocladan-16α,19-diol (2), cembrane diterpene ovatodiolide (3), sitosteryl-3-O-β-d-glucoside (4), and verbascoside (5), were isolated from aerial parts of Anisomeles heyneana. The structure of compound 1 was elucidated by 1D and 2D NMR analyses which included HSQC, HMBC, and nuclear overhauser effect spectroscopy (NOESY) experiments as well as X-ray crystallography. This is the first report of phyllocladane diterpenes from genus Anisomeles. Compounds 1, 3, 4, and 5 were evaluated for inhibition of Mycobacterium tuberculosis and 3 was found to exhibit anti-mycobacterial activity with IC90 6.53 μg/ml. Compounds 1, 3, and 5, at 100 μg/ml, were also evaluated for inhibition of Thp-1 cell lines, and compounds 1 and 3 showed 59.02% and 96.4% inhibitions, respectively.

ChemInform Abstract: Synthesis and in vitro Antitubercular Activity of 4‐Aryl/Alkylsulfonylmethylcoumarins as Inhibitors of Mycobacterium tuberculosis.

AbstractEighteen title compounds of type (IV) are prepared and tested as inhibitors of the title species.

Design, Synthesis and Study of Reactive Oxygen Species Generators as Mycobacterium Tuberculosis Inhibitors

Design, Synthesis and Study of Reactive Oxygen Species Generators as Mycobacterium Tuberculosis Inhibitors

Nitroalkene Oleic Acid Irreversibly Inhibited Mycobacterium Tuberculosis PknG by Electrophilic Attack to Cysteins in the Non-Catalytic Rubredoxin Domain

Nitroalkene Oleic Acid Irreversibly Inhibited Mycobacterium Tuberculosis PknG by Electrophilic Attack to Cysteins in the Non-Catalytic Rubredoxin Domain

MmPPOX Inhibits Mycobacterium tuberculosis Lipolytic Enzymes Belonging to the Hormone-Sensitive Lipase Family and Alters Mycobacterial Growth

Lipid metabolism plays an important role during the lifetime of Mycobacterium tuberculosis, the causative agent of tuberculosis. Although M. tuberculosis possesses numerous lipolytic enzymes, very few have been characterized yet at a biochemical/pharmacological level. This study was devoted to the M. tuberculosis lipolytic enzymes belonging to the Hormone-Sensitive Lipase (HSL) family, which encompasses twelve serine hydrolases closely related to the human HSL. Among them, nine were expressed, purified and biochemically characterized using a broad range of substrates. In vitro enzymatic inhibition studies using the recombinant HSL proteins, combined with mass spectrometry analyses, revealed the potent inhibitory activity of an oxadiazolone compound, named MmPPOX. In addition, we provide evidence that MmPPOX alters mycobacterial growth. Overall, these findings suggest that the M. tuberculosis HSL family displays important metabolic functions, thus opening the way to further investigations linking the involvement of these enzymes in mycobacterial growth.

Synthesis and evaluation of novel 1,3,4-oxadiazole derivatives of marine bromopyrrole alkaloids as antimicrobial agent

In an attempt to identify new potential lead as antimicrobial agent, twenty hybrids of marine bromopyrrole alkaloids with 1,3,4-oxadiazole were designed based on molecular hybridization technique and synthesized. Synthesized molecules were evaluated for their antibacterial, antifungal and antitubercular activities. Hybrids 5d, 5i, 5j and 5k exhibited equivalent antibacterial activity (MIC of 1.56μg/mL) compared with standard drug ciprofloxacin against Staphylococcus aureus and Escherichia coli. Equal antifungal activity (MIC of 1.56μg/mL) was shown by of hybrids 5j, 5k and 7d compared with standard Amphotericin-B. The inhibition of Mycobacterium tuberculosis at concentrations as low as 1.6 and 1.5μg/mL by compounds 5f and 7d respectively indicates that these compounds can act as leads for development of newer anti-TB compounds.

Potential Use of Nitrate Reductase as a Biomarker for the Identification of Active and Dormant Inhibitors of Mycobacterium tuberculosis in a THP1 Infection Model

The development of a macrophage-based, antitubercular high-throughput screening system could expedite discovery programs for identifying novel inhibitors. In this study, the kinetics of nitrate reduction (NR) by Mycobacterium tuberculosis during growth in Thp1 macrophages was found to be almost parallel to viable bacilli count. NR in the culture medium containing 50 mM of nitrate was found to be optimum on the fifth day after infection with M. tuberculosis. The signal-to-noise (S/N) ratio and Z-factor obtained from this macrophage-based assay were 5.4 and 0.965, respectively, which confirms the robustness of the assay protocol. The protocol was further validated by using standard antitubercular inhibitors such as rifampicin, isoniazid, streptomycin, ethambutol, and pyrazinamide, added at their IC90 value, on the day of infection. These inhibitors were not able to kill the bacilli when added to the culture on the fifth day after infection. Interestingly, pentachlorophenol and rifampicin killed the bacilli immediately after addition on the fifth day of infection. Altogether, this assay protocol using M. tuberculosis–infected Thp-1 macrophages provides a novel, cost-efficient, robust, and easy-to-perform screening platform for the identification of both active and hypoxic stage-specific inhibitors against tuberculosis.

Synthesis and in vitro antitubercular activity of 4-aryl/alkylsulfonylmethylcoumarins as inhibitors of Mycobacterium tuberculosis

A series of 4-aryl/alkylsulfonylmethylcoumarins have been synthesized and screened for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv (MTB). Four of the compounds showed MIC in the range of 0.78–3.13μg/mL proving their potential activity.

Evaluation of Small Molecule Tuberculostats for Targeting Tuberculosis Infections of the Central Nervous System

Tuberculosis infection of the central nervous system is a serious and frequently fatal disease. Four drugs have been found to very efficiently inhibit the growth of Mycobacterium tuberculosis and are examined for molecular properties that enable penetration of the blood-brain barrier. Drugs 1, 2, and 3 are aromatic compounds having a single bromine atom in ortho, meta, and para-position, respectively, relative to the hydrazide group (-C(O)NHNH2). A paraposition for bromine enabled the strongest inhibition of Mycobacterium tuberculosis. Drug 4 is a hydrazide derivative of ciprofloxacin. All drugs showed molecular properties suitable for targeting tuberculosis infections of the central nervous system. Drugs 1, 2, 3, 4, and isoniazid showed zero violations of the Rule of 5 and potential capability for oral administration. Values of BB (Cbrain/Cblood) suggested that drugs 1, 2, and 3 will be able to penetrate the brain approximately three times greater than isoniazid. Similarly, the calculated value of BB for drug 4 is comparable to that of isoniazid. Calculated values of polar surface area for drugs 1, 2, 3, and isoniazid indicated a potential rate of intestinal absorption of greater than 75% of drug amount present. The intestinal absorption of drug 4 is predicted to be greater than 50% of total amount present. Drug concentrations necessary for achieving MIC50 for 1, 2, 3, 4, and isoniazid are determined to be 65.9 μg/mL, 29.5 μg/mL, 21.5 μg/mL, 36.4 μg/mL, and 16.7 μg/mL, respectively. The position of the bromine atom within drugs 1, 2, and 3 appears to substantially influence the effectiveness of growth inhibition. These compounds show substantial potential for targeting tuberculosis infections within the central nervous system.

Design, Synthesis, and Structure–Activity Correlations of Novel Dibenzo[b,d]furan, Dibenzo[b,d]thiophene, and N-Methylcarbazole Clubbed 1,2,3-Triazoles as Potent Inhibitors of Mycobacterium tuberculosis

A molecular hybridization approach is an emerging structural modification tool to design new molecules with improved pharmacophoric properties. In this study, 1,2,3-triazole-based Mycobacterium tuberculosis inhibitors and synthetic and natural product-based tricyclic (carbazole, dibenzo[b,d]furan, and dibenzo[b,d]thiophene) antimycobacterial agents were integrated in one molecular platform to prepare various novel clubbed 1,2,3-triazole hybrids using click chemistry. Structure-activity correlations and in vitro activity against M. tuberculosis strain H37Rv of new analogues revealed the order: dibenzo[b,d]thiophene > dibenzo[b,d]furan > 9-methyl-9H-carbazole series. Two of the most potent M. tuberculosis inhibitors 13h and 13q with MIC = 0.78 μg/mL (∼1.9 μM) displayed a low cytotoxicity and high selectivity index (50-255) against four different human cancer cell lines. These results together provided the potential importance of molecular hybridization and the development of triazole clubbed dibenzo[b,d]thiophene-based lead candidates to treat mycobacterial infections.

Regulation of Mycobacterium tuberculosis-Dependent HIV-1 Transcription Reveals a New Role for NFAT5 in the Toll-Like Receptor Pathway

Tuberculosis (TB) disease in HIV co-infected patients contributes to increased mortality by activating innate and adaptive immune signaling cascades that stimulate HIV-1 replication, leading to an increase in viral load. Here, we demonstrate that silencing of the expression of the transcription factor nuclear factor of activated T cells 5 (NFAT5) by RNA interference (RNAi) inhibits Mycobacterium tuberculosis (MTb)-stimulated HIV-1 replication in co-infected macrophages. We show that NFAT5 gene and protein expression are strongly induced by MTb, which is a Toll-like receptor (TLR) ligand, and that an intact NFAT5 binding site in the viral promoter of R5-tropic HIV-1 subtype B and subtype C molecular clones is required for efficent induction of HIV-1 replication by MTb. Furthermore, silencing by RNAi of key components of the TLR pathway in human monocytes, including the downstream signaling molecules MyD88, IRAK1, and TRAF6, significantly inhibits MTb-induced NFAT5 gene expression. Thus, the innate immune response to MTb infection induces NFAT5 gene and protein expression, and NFAT5 plays a crucial role in MTb regulation of HIV-1 replication via a direct interaction with the viral promoter. These findings also demonstrate a general role for NFAT5 in TLR- and MTb-mediated control of gene expression.

Combining Cheminformatics Methods and Pathway Analysis to Identify Molecules with Whole-Cell Activity Against Mycobacterium Tuberculosis

New strategies for developing inhibitors of Mycobacterium tuberculosis (Mtb) are required in order to identify the next generation of tuberculosis (TB) drugs. Our approach leverages the integration of intensive data mining and curation and computational approaches, including cheminformatics combined with bioinformatics, to suggest biological targets and their small molecule modulators. We now describe an approach that uses the TBCyc pathway and genome database, the Collaborative Drug Discovery database of molecules with activity against Mtb and their associated targets, a 3D pharmacophore approach and Bayesian models of TB activity in order to select pathways and metabolites and ultimately prioritize molecules that may be acting as substrate mimics and exhibit activity against TB. In this study we combined the TB cheminformatics and pathways databases that enabled us to computationally search >80,000 vendor available molecules and ultimately test 23 compounds in vitro that resulted in two compounds (N-(2-furylmethyl)-N'-[(5-nitro-3-thienyl)carbonyl]thiourea and N-[(5-nitro-3-thienyl)carbonyl]-N'-(2-thienylmethyl)thiourea) proposed as mimics of D-fructose 1,6 bisphosphate, (MIC of 20 and 40 μg/ml, respectively). This is a simple yet novel approach that has the potential to identify inhibitors of bacterial growth as illustrated by compounds identified in this study that have activity against Mtb.

ChemInform Abstract: Efficient Synthesis and in vitro Antitubercular Activity of 1,2,3‐Triazoles as Inhibitors of Mycobacterium tuberculosis.

AbstractAn environmentally friendly, solvent‐free protocol for the efficient and rapid synthesis of 1,2,3‐triazoles (III) is achieved using Huisgen′s 1,3‐dipolar cycloaddition.

Screening, Identification, and Characterization of Mechanistically Diverse Inhibitors of the Mycobacterium Tuberculosis Enzyme, Pantothenate Kinase (CoaA)

The authors describe the discovery of anti-mycobacterial compounds through identifying mechanistically diverse inhibitors of the essential Mycobacterium tuberculosis (Mtb) enzyme, pantothenate kinase (CoaA). Target-driven drug discovery technologies often work with purified enzymes, and inhibitors thus discovered may not optimally inhibit the form of the target enzyme predominant in the bacterial cell or may not be available at the desired concentration. Therefore, in addition to addressing entry or efflux issues, inhibitors with diverse mechanisms of inhibition (MoI) could be prioritized before hit-to-lead optimization. The authors describe a high-throughput assay based on protein thermal melting to screen large numbers of compounds for hits with diverse MoI. Following high-throughput screening for Mtb CoaA enzyme inhibitors, a concentration-dependent increase in protein thermal stability was used to identify true binders, and the degree of enhancement or reduction in thermal stability in the presence of substrate was used to classify inhibitors as competitive or non/uncompetitive. The thermal shift–based MoI assay could be adapted to screen hundreds of compounds in a single experiment as compared to traditional biochemical approaches for MoI determination. This MoI was confirmed through mechanistic studies that estimated Kie and Kies for representative compounds and through nuclear magnetic resonance–based ligand displacement assays.

Synthesis and antimalarial and antituberculosis activities of a series of natural and unnatural 4-methoxy-6-styryl-pyran-2-ones, dihydro analogues and photo-dimers

Previous studies have identified the 3,6-dialkyl-4-hydroxy-pyran-2-one marine microbial metabolites pseudopyronines A and B to be modest growth inhibitors of Mycobacterium tuberculosis and a range of tropical diseases including Plasmodium falciparum and Leishmania donovani. In an effort to expand the structure–activity relationship of this compound class towards infectious diseases, a library of natural product and natural product-like 4-methoxy-6-styryl-pyran-2-ones and a subset of catalytically reduced examples were synthesized. In addition, the photochemical reactivity of several of the 4-methoxy-6-styryl-pyran-2-ones were investigated yielding head-to-head and head-to-tail cyclobutane dimers as well as examples of asymmetric aniba-dimer A-type dimers. All compounds were evaluated for cytotoxicity and activity against M. tuberculosis, P. falciparum, L. donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi. Of the styryl-pyranones, natural product 3 and non-natural styrene and naphthalene substituted examples 13, 18, 21, 22 and 23 exhibited antimalarial activity (IC50 <10μM) with selectivity indices (SI) >10. Δ7 Dihydro analogues were typically less active or lacked selectivity. Head-to-head and head-to-tail photodimers 5 and 34 exhibited moderate IC50s of 2.3 to 17μM towards several of the parasitic organisms, while the aniba-dimer-type asymmetric dimers 31 and 33 were identified as being moderately active towards P. falciparum (IC50 1.5 and 1.7μM) with good selectivity (SI ∼80). The 4-tert-butyl aniba-dimer A analogue 33 also exhibited activity towards L. donovani (IC50 4.5μM), suggesting further elaboration of this latter scaffold could lead to the identification of new leads for the dual treatment of malaria and leishmaniasis.

Syntheses of mycobactin analogs as potent and selective inhibitors of Mycobacterium tuberculosis

Three analogs of mycobactin T, the siderophore secreted by Mycobacterium tuberculosis (Mtb) were synthesized and screened for their antibiotic activity against Mtb H(37)Rv and a broad panel of Gram-positive and Gram-negative bacteria. The synthetic mycobactins were potent (MIC(90) 0.02-0.88 μM in 7H12 media) and selective Mtb inhibitors, with no inhibitory activity observed against any other of the microorganisms tested. The maleimide-containing analog 40 represents a versatile platform for the development of mycobactin-drug conjugates, as well as other applications.

Synthesis and in vitro anti-tubercular evaluation of 1,2,3-triazole tethered β-lactam–ferrocene and β-lactam–ferrocenylchalcone chimeric scaffolds

Twenty different triazoles were prepared to probe the anti-tubercular structure-activity relationships (SAR) within the β-lactam-ferrocene-triazole conjugate family. The compounds have been synthesized by copper-catalyzed "click chemistry". In vitro anti-tubercular activity was determined for each compound but the synthesized hybrids failed to inhibit Mycobacterium tuberculosis growth even at high doses. The manuscript assumes significance as this is the first report on the inclusion of ferrocene nucleus in the well established β-lactam family via triazole linkers with reputed physicochemical profiles.