High Antimycobacterial Activity Research Articles

Both Nitro Groups Are Essential for High Antitubercular Activity of 3,5-Dinitrobenzylsulfanyl Tetrazoles and 1,3,4-Oxadiazoles through the Deazaflavin-Dependent Nitroreductase Activation Pathway.

3,5-Dinitrobenzylsulfanyl tetrazoles and 1,3,4-oxadiazoles, previously identified as having high in vitro activities against both replicating and nonreplicating mycobacteria and favorable cytotoxicity and genotoxicity profiles were investigated. First we demonstrated that these compounds act in a deazaflavin-dependent nitroreduction pathway and thus require a nitro group for their activity. Second, we confirmed the necessity of both nitro groups for antimycobacterial activity through extensive structure-activity relationship studies using 32 structural types of analogues, each in a five-membered series. Only the analogues with shifted nitro groups, namely, 2,5-dinitrobenzylsulfanyl oxadiazoles and tetrazoles, maintained high antimycobacterial activity but in this case mainly as a result of DprE1 inhibition. However, these analogues also showed increased toxicity to the mammalian cell line. Thus, both nitro groups in 3,5-dinitrobenzylsulfanyl-containing antimycobacterial agents remain essential for their high efficacy, and further efforts should be directed at finding ways to address the possible toxicity and solubility issues, for example, by targeted delivery.

Synthesis and antituberculosis activity of new 5-alkynyl derivatives of 2-thiouridine: application of new scaffold

We herein describe new potent inhibitors of mycobacteria based on 5-substituted 2-thiouridine derivatives. A series of new 5-alkynyl-substituted 2-thiouridine derivatives were synthesized via palladium-catalysed Sonogashira cross-coupling reaction of 5-iodo-2-thiopyrimidine base with terminal acetylenes with good yields in DMF at room temperature. It was found that sulfur atom in C2 position of pyrimidine ring had no impact on yields of target compounds. All obtained compounds were evaluated for their antimycobacterial activity against Mycobacetrium bovis and Mycobacterium tuberculosis at concentrations of 0.1-100 µg/ml using MABA test. Synthesized nucleosides showed high antimycobacterial activity against Mycobacterium bovis and Mycobacteri um tuberculosis. The obtained MIC50 values of 2-thionucleosides 14, 15 and 16 (0.28-0.75 µg/ml) significantly exceed characteristics of reference drug rifampicin, D-cycloserine and isoniazid, which gives prerequisites for further more detailed studies.

Synthesis and Antitubercular Activity of New 5-Alkynyl Derivatives of 2-Thiouridine

New efficient mycobacterial inhibitors based on 5-substituted 2-thiouridine derivatives have been described. A series of new 5-alkynyl-substituted 2-thiouridines have been synthesized in good yields by the palladium-catalyzed Sonogashira cross-coupling of 5-iodo-2-thiopyrimidine base with terminal alkynes in DMF at room temperature. The presence of a sulfur atm at C2 of the pyrimidine ring has been shown not to affect the yield of the target compounds. The synthesized 2-thiouridine derivatives were evaluated for their antimyco­bacterial activity against Mycobacterium bovis and Mycobacterium tuberculosis at concentrations of 0.1 to 100 μg/mL using microplate Alamar Blue assay (MABA). The compounds showed high antimycobacterial activity against both tested strains. The MIC50 values for 2-thionucleosides 14–16 (0.28–0.75 μg/mL) were much superior to those of the reference drugs rifampicin, D-cycloserine, and isoniazid, which makes these compounds promising for further more detailed study.

Novel Derivatives of Quinoxaline-2-carboxylic Acid 1,4-Dioxides as Antimycobacterial Agents: Mechanistic Studies and Therapeutic Potential.

The World Health Organization (WHO) reports that tuberculosis (TB) is one of the top 10 leading causes of global mortality. The increasing incidence of multidrug-resistant TB highlights the urgent need for an intensified quest to discover innovative anti-TB medications In this study, we investigated four new derivatives from the quinoxaline-2-carboxylic acid 1,4-dioxide class. New 3-methylquinoxaline 1,4-dioxides with a variation in substituents at positions 2 and 6(7) were synthesized via nucleophilic aromatic substitution with amines and assessed against a Mycobacteria spp. Compound 4 showed high antimycobacterial activity (1.25 μg/mL against M. tuberculosis) and low toxicity in vivo in mice. Selection and whole-genomic sequencing of spontaneous drug-resistant M. smegmatis mutants revealed a high number of single-nucleotide polymorphisms, confirming the predicted mode of action of the quinoxaline-2-carboxylic acid 1,4-dioxide 4 as a DNA-damaging agent. Subsequent reverse genetics methods confirmed that mutations in the genes MSMEG_4646, MSMEG_5122, and MSMEG_1380 mediate resistance to these compounds. Overall, the derivatives of quinoxaline-2-carboxylic acid 1,4-dioxide present a promising scaffold for the development of innovative antimycobacterial drugs.

Synthesis, Biological Evaluation and Computational Studies of New Hydrazide Derivatives Containing 1,3,4-Oxadiazole as Antitubercular Agents

To extend our screening for novel antimycobacterial molecules, we have designed, synthesized, and biologically evaluated a library of 14 new hydrazide derivatives containing 1,3,4-oxadiazole core. A variety of mycobacterial strains, including some drug-resistant strains, were tested for antimycobacterial activity. Among the compounds tested, five showed high antimycobacterial activity (MIC values of 8 μg/mL) against M. tuberculosis H37Ra attenuated strain, and two derivatives were effective (MIC of 4 µg/mL) against pyrazinamide-resistant strains. Furthermore, the novel compounds were tested against the fungal C. albicans strain, showing no antimycotic activity, and thus demonstrating a good selectivity profile. Notably, they also exhibited low cytotoxicity against human SH-SY5Y cells. The molecular modeling carried out suggested a plausible mechanism of action towards the active site of the InhA enzyme, which confirmed our hypothesis. In conclusion, the active compounds were predicted in silico for ADME properties, and all proved to be potentially orally absorbed in humans.

Development of 6-Methanesulfonyl-8-nitrobenzothiazinone Based Antitubercular Agents.

The 6-trifluoro substituted 8-nitrobenzothiazinones (BTZs) represent a novel type of antitubercular agents, and their high antimycobacterial activity is related to the inhibition of decaprenylphosphoryl-β-d-ribose 2'-oxidase (DprE1), an enzyme essential for the biosynthesis of mycobacterial cell wall. While extraordinary whole-cell activity was reported for the clinically advanced compound PBTZ169, its poor aqueous solubility signals the potential low bioavailability. To ameliorate the BTZ physiochemical property, a series of 6-methanesulfonyl substituted compounds were designed and prepared, and their antitubercular activity and DprE1 inhibition ability were evaluated. Among these compounds, MsPBTZ169 and compounds 2 and 8 exhibited minimum inhibitory concentrations (MICs) of less than 40 nM; moreover, these compounds displayed increased aqueous solubility and acceptable metabolic stability. Taken together, this study suggested that the 6-methanesulfonyl substituted 8-nitrobenzothiazinone derivatives, in combination with side chain modification, might provide BTZ type antitubercular agents with improved drug-like properties.

Synthesis, Biological Profile, and Molecular Docking of Some New Bis- Imidazole Fused Templates and Investigation of their Cytotoxic Potential as Anti-tubercular and/or Anticancer Prototypes.

There is a great need to discover more drugs with antimycobacterial activities to fight lung cancer and tuberculosis (two of the deadliest diseases worldwide). To our knowledge, the present study is the first to report the antimycobacterial activity of imidazole-fused heterocycles. Construction of some bis-imidazole fused heterocycles with potential anti-tubercular and/or potent antitumor activities. A series of bis-imidazole fused derivatives 6-8 and 13-16 was constructed using bisphenacyl bromide derivative 2 as a synthetic platform. Compound 2 was also used to access bisquinoxaline 20, bis-benzothiazine derivatives 23, and bis-thiazolopyrimidine derivatives 26. The new bis-imidazole derivatives were evaluated for their anticancer activity against the lung carcinoma cell line (A-549) using Cisplatin as a reference drug. The new compounds were also screened for their anti-tubercular activity against M. tuberculosis (ATCC 25177) using Isoniazid as a reference drug. Among the new bis-imidazole derivatives, three examples showed remarkable antitumor activities while five other compounds showed high antimycobacterial activity. A novel series of bis-imidazole fused heterocycles was developed. Multiple prototypes of this new series showed remarkable anti-tubercular and/or potent antitumor activities.

Design and synthesis of novel 5-alkynyl pyrimidine nucleosides derivatives: Influence of C-6-substituent on antituberculosis activity

We herein report new 5-substituted uridine derivatives as potent inhibitors of mycobacteria – causative agents of tuberculosis. A series of new 5-alkynyl-substituted uridine derivatives were synthesised via palladium-catalysed Sonogashira cross-coupling reaction of 5-iodo-6-methylpyrimidine base with terminal acetylenes with good yields in DMF at room temperature. It was found that methyl group in C-6 position of pyrimidine ring had no impact on yields of target compounds. All obtained compounds were evaluated for their antimycobacterial activity against Mycobacetrium bovis and Mycobacterium tuberculosis at concentrations of 1–100 µg/ml using MABA test. Synthesized nucleosides showed high antimycobacterial activity against M. bovis and M. Tuberculosis. The MIC50 values of 11 and 13 were similar or close to that of the reference drug rifampicin.

Fragment-based approach to novel bioactive purine derivatives

Abstract Using purine as a scaffold, the methods for preparation of novel 2-aminopurine and purine derivatives substituted at position C 6 by the fragments of natural amino acids, short peptides, and N-heterocycles, including enantiopure ones, have been proposed. The methods for determination of the enantiomeric purity of the obtained chiral compounds have been developed. Conjugates exhibiting high antimycobacterial or anti-herpesvirus activity against both laboratory and multidrug-resistant strains were revealed among the obtained compounds.

Structural Modifications of 3-Triazeneindoles and Their Increased Activity Against Mycobacterium tuberculosis.

We synthesized 100 novel indole-based compounds with polyaza-functionalities, including 3-triazeneindoles, and tested their activity in vitro against laboratory M. tuberculosis H37Rv and clinical izoniazid-resistant CN-40 isolates, using gross and fine titration approaches. Here we present a few 3-triazeneindoles with the highest anti-mycobacterial activity. Introduction of short lipid tails into the 3-triazeneindole core additionally increased their activity against mycobacteria engulfed by murine macrophages. We also demonstrate that the compound TU112, one of the most active in our previous study, being not bioavailable after administration in mice per os, manifests prominent anti-mycobacterial activity after intravenous or aerosol delivery, as assessed by the mouse serum and lung supernatant titration assays.

The synthesis and antituberculosis activity of 5-alkynyl uracil derivatives

A series of new 5-alkynyl-substituted uracil and uridine derivatives were synthesised via palladium-catalysed Sonogashira cross-coupling reaction of 5-bromo-pyrimidine base with terminal acetylenes with good yields in DMF at room temperature. All obtained compounds were tested for antimycobacterial activity against Mycobacetrium bovis and Mycobacterium tuberculosis (H37Ra) at concentrations of 1–100 µg/ml using MABA test. Obtained results revealed that most of tested uracil derivatives exhibited high antimycobacterial activity (MIC50 = 1.1–19.2 µg/ml) in comparison with therapeutic agents such as rifampicin, isoniazid and d-cycloserine, excluding compounds having alkyl substituent at triple alkyne bond.

Design, synthesis and antimycobacterial activity of thiazolidine-2,4-dione-based thiosemicarbazone derivatives.

The two series of thiosemicarbazone derivatives with thiazolidine-2,4-dione (TZD) core were designed and synthesized. The antimycobacterial activity of the target compounds was tested against Mycobacterium tuberculosis H37Ra by broth microdilution method with resazurin as an indicator of the metabolic activity of mycobacteria. Conducted studies revealed antimycobacterial activity in the concentration range of 0.031-64µg/ml for 31 synthesized derivatives with TZD core. The highest antimycobacterial activity (MIC=0.031-0.125µg/ml) was demonstrated for the new group of compounds: TZD-based hybrids with 4-unsubstituted thiosemicarbazone substituent. Furthermore, all the tested compounds within this group were characterized by low cytotoxicity. Among tested compounds, two compounds are the most promising potential antimycobacterial agents since they not only show very low MIC values, but also non-toxicity against Vero cells at tested concentration range. High effectiveness and safety of these synthesized compounds makes them promising candidates as antimycobacterial agents.

Synthesis and antimycobacterial activity of thiazolidine-2,4-dione based derivatives with halogenbenzohydrazones and pyridinecarbohydrazones substituents

The two series of thiazolidine-2,4-dione (TZD) based hybrids with halogenbenzohydrazones and pyridinecarbohydrazones substituents were designed and synthesized. Target hydrazones were evaluated for their antimycobacterial activity by broth microdilution method with resazurin as an indicator of the metabolic activity of mycobacteria. Conducted studies revealed antimycobacterial activity in the concentration range of 1–512 μg/ml for 23 synthesized TZD-based derivatives. The highest antimycobacterial activity (MIC = 1 μg/ml) was demonstrated for the new group of compounds: TZD-based derivatives with pyridine-4-carbohydrazone substituent. Furthermore, all the tested compounds within this group were characterized by low cytotoxicity. On the basis of the results obtained, three compounds with the highest SI were selected. High effectiveness and safety of these synthesized derivatives makes them promising candidates as antimycobacterial agents.

N-Trifluoromethylthiolated Sulfonimidamides and Sulfoximines: Anti-microbial, Anti-mycobacterial, and Cytotoxic Activity.

Herein we demonstrate the expanded utility of a recently described N-trifluoromethylthiolation protocol to sulfonimidamide containing substances. The novel N-trifluoromethylthio sulfonimidamide derivatives thus obtained were evaluated for antibacterial activity against Mycobacterium tuberculosis (M. tb.) and Mycobacterium abscessus and Gram + Ve (Streptococcus aureus, Bacillus subtilis), and Gram - Ve (Escherichia coli, Pseudomonas aeruginosa) bacteria. Two compounds, 13 and 15 showed high antimycobacterial activity with MIC value of 4-8 μg/mL; i.e. comparable to WHO recommended first line antibiotic for TB infection ethambutol. The same compounds were also found to be cytotoxic in HepG2 cells (compound 13 IC50 = 15 μg/mL; compound 15 IC50 = 65 μg/mL). A structure activity relationship, using matched pair analysis, gave the unexpected conclusion that the trifluoromethylthio moiety was responsible for the cellular and bacterial toxicity. Given the increasing use of the trifluoromethylthio group in contemporary medicinal chemistry, this observation calls for considerations before implementation of the functionality in drug design.

Design, synthesis and antimycobacterial activity of benzoxazinone derivatives and open-ring analogues: Preliminary data and computational analysis.

This study examines in depth benzoxazine nucleus for antimycobacterial property. We synthesized some benzoxazin-2-one and benzoxazin-3-one derivatives, which were tested for activity against a panel of Mycobacterium tuberculosis (Mtb) strains, including H37Ra, H37Rv and some resistant strains. Several compounds displayed a high antimycobacterial activity and the three isoniazid analogue derivatives 8a-c exhibited a MIC range of 0.125-0.250 μg/mL (0.37-0.75 μM) against strain H37Ra, therefore lower than the isoniazid reference drug. Two benzoxazin-2-one derivatives, 1c and 5j, together with isoniazid-analogue compound 8a, also revealed low MIC values against resistant strains and proved highly selective for mycobacterial cells, compared to mammalian Vero cells. To predict whether molecule 8a is able to interact with the active site of InhA, we docked it into the crystal structure; indeed, during the molecular dynamic simulation the compound never left the protein pocket. The more active compounds were predicted for ADME properties and all proved to be potentially orally active in humans.

The preclinical candidate indole-2-carboxamide improves immune responses to Mycobacterium tuberculosis infection in healthy subjects and individuals with type 2 diabetes.

A novel group of agents known as the indole-2-carboxamides (often referred to as indoleamides) have been shown to demonstrate high antimycobacterial activity. Studies have demonstrated that the best indoleamides possess desirable ADME/Tox properties, with less adverse effects and increased efficacy against both MDR-TB (multi-drug resistant TB) and XDR-TB (extensively drug-resistant TB). The primary mechanism of killing Mycobacterium tuberculosis (Mtb) by indoleamides is by disrupting the function of the essential mycolic acid transporter MmpL3 protein (Mycobacterial membrane protein Large 3). Therefore, targeting this essential mycobacterial transporter by small molecules opens new possibility for the development of novel and effective anti-TB agents. In the present study, we characterized the effects of indoleamides in altering the viability of Mtb in an in vitro granuloma model using immune cells derived from healthy subjects and those with type 2 diabetes mellitus (T2DM). Our results indicate that treatment with the best indoleamide 3 resulted in a significant reduction in the viability of Mtb in both THP-1 macrophages as well as in granulomas derived from healthy individuals and subjects with T2DM. Graphical Abstract.

Evaluation of antimycobacterial activity from marine and freshwater microalgae

Tuberculosis is considered one of the most important epidemiological diseases worldwide. The current treatment for tuberculosis is a combination of antituberculosis drugs for at least 9 months. Nowadays, the search for new pharmacological agents for the treatment of tuberculosis is an urgent endeavor. Microalgae produce a wide variety of molecules that possess biological activities of pharmaceutical interest. Therefore, the objective of this work was to evaluate the antimycobacterial activity of hexane crude extracts of 6 microalgae: Chlamydomonas mexicana, Porphyridium cruentum, Isochrysis galbana, Rhodomonas sp., Aphanocapsa marina, and Nitzschia palea. All of the hexane extracts inhibited at least 90% of the growth of Mycobacterium tuberculosis H37Rv at a concentration of 100 μg ml-1. The hexane crude extract of I. galbana had the highest antimycobacterial activity displaying a percentage inhibition that was equal to that of the antituberculosis drug isoniazid and having a minimum inhibitory concentration of 50 μg ml-1. These findings demonstrate that microalgae are an excellent source for the search of novel antimycobacterial compounds.

Design, synthesis, characterization and antitubercular activity of some nov-el 2, 4-disubstituted thiazole derivatives

Literature reviews reveal that thiazole and pyrazine carboxamide derivatives exhibit anticonvulsant, antimicrobial, anticancer and anti-tubercular activities due to the presence of –S-C=N- and-CO–NH- moiety. A series of thiazolyl pyrazine carboxamide derivatives (5a-j) were synthesized by condensation reaction between 2-amino, 4-substituted phenyl 2-amino thiazole and pyrazine 2-carboxylic acid. These synthesized thiazole derivatives (5a-j) were evaluated for their inhibitory activity against Mycobacterium tuberculosis (Mtb), H37Rv using microplate Alamar Blue assay (MABA). The compound, 5c and 5h showed high anti-mycobacterial activity with MIC value of 6.25 µg/ml, and the compound 5g also exhibited anti-mycobacterial activity with MIC value of 12.50 µg/ml. Molecular docking studies of these synthesized molecules with b-Ketoacyl-ACP Synthase (KasA) protein of Mycobacterium tuberculosis (Mtb) have been carried out to understand the mechanism of anti-mycobacterial action.

New indole and indazole derivatives as potential antimycobacterial agents

The study reports on the synthesis and in vitro assessment of the antimycobacterial activity of a series of new indole- and indazole-based aroylhydrazones evaluated against Mycobacterium tuberculosis H37Rv. Isoniazide and ethambutol were used as reference drugs. The most active compounds 3a (MIC 0.4412 μM) and 3e (MIC 0.3969 μM) demonstrated excellent antimycobacterial activity, a very low toxicity against the human embryonic kidney cell line HEK-293T and high selectivity index values (SI = 633.49 and SI > 1978.83, respectively). Importantly, the oral administration of compound 3e at the highest dose of 2000 mg/kg b.w. resulted in no mortalities or evidence of adverse effects, implying that compound 3e is nontoxic. The other derivatives with an indole and indazole scaffold also exhibited high antimycobacterial activity with exception of indole derivatives with Br substituents at the 5th position which exhibited activity weaker than that of ethambutol. The molecular docking investigations performed in an enoyl-ACP reductase (InhA) displayed good docking scores and promising insights on possible interactions with the InhA receptor.

In-vitro evaluation of the antibacterial activity of the essential oils of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa against strains of Mycobacterium tuberculosis (including MDR), Mycobacterium kansasii and Mycobacterium gordonae

BackgroundMycobacterium spp. are responsible for several diseases, particularly in immunocompromised populations. The spreading of the resistance to antimycobacterial drugs is a significant problem to the public health and requires to find out a new and innovative alternative for the treatment of drug resistant mycobacterial strains. In this study, the antimycobacterial activity of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa essential oils extracted from Lebanese plants was investigated against selected Mycobacterium spp. strains. MethodsSeveral dilutions of the three aforementioned essential oils were studied for antimycobacterial activity against four Mycobacterium spp. strains: Mycobacterium tuberculosis subsp. tuberculosis (ATCC® 27294™), multidrug-resistant M. tuberculosis (CMUL 157), Mycobacterium kansasii Hauduroy (ATCC® 12478™) and Mycobacterium gordonae Bojalil et al. (ATCC® 14470™). ResultsEven with high dilutions, all tested essential oils showed a high antimycobacterial activity against targeted strains. Our data showed that M. barbata, E. globulus and J. excelsa essential oils totally inhibit the mycobacterial growth whatever the tested strains for the dilution 1/250, 1/100 and 1/250, respectively. ConclusionTo our knowledge, this is the first study regarding the antimycobacterial activity of essential oils in Lebanon. Our data show promising results, and encourage to investigate more on these medicinal plants, especially M. barbata.