Fighting tuberculosis: An old disease with new challenges

Alkaloids as potential anti-tubercular agents

An increasing incidence of deaths due to tuberculosis and the known drawbacks of the current existing drugs including the emergence of multi drug-resistant strains have led to a renewed interest in the discovery of new anti-tubercular agents with novel modes of actions. The recent researches focused on natural products have shown a useful way to obtain a potentially rich source of drug candidates, where alkaloids have been found more effective. The present review focuses on current epidemiology of tuberculosis, synergy of the disease with HIV, current therapy, available molecular targets and, highlights why natural products especially alkaloids are so important. The review summarizes alkaloids found active against mycobacteria from the mid-1980s to late 2008 with special attention on the study of structure-activity relationship (SAR).

Structure-activity relationships of macrolides against Mycobacterium tuberculosis

Existing 14, 15 and 16-membered macrolide antibiotics, while effective for other bacterial infections, including some mycobacteria, have not demonstrated significant efficacy in tuberculosis. Therefore an attempt was made to optimize this class for activity against Mycobacterium tuberculosis through semisyntheses and bioassay. Approximately 300 macrolides were synthesized and screened for anti-TB activity. Structural modifications on erythromycin were carried out at positions 3, 6, 9, 11, and 12 of the 14-membered lactone ring; as well as at position 4'' of cladinose and position 2' of desosamine. In general, the synthesized macrolides belong to four subclasses: 9-oxime, 11,12-carbamate, 11,12-carbazate, and 6-O-substituted derivatives. Selected compounds were assessed for mammalian cell toxicity and in some cases were further assessed for CYP3A4 inhibition, microsome stability, in vivo tolerance and efficacy. The activity of 11,12-carbamates and carbazates as well as 9-oximes is highly influenced by the nature of the substitution at these positions. For hydrophilic macrolides, lipophilic substitution may result in enhanced potency, presumably by enhanced passive permeation through the cell envelope. This strategy, however, has limitations. Removal of the C-3 cladinose generally reduces the activity. Acetylation at C-2' or 4'' maintains potency of C-9 oximes but dramatically decreases that of 11,12-substituted compounds. Further significant increases in the potency of macrolides for M. tuberculosis may require a strategy for the concurrent reduction of ribosome methylation.

A natural carbohydrate substrate for Mycobacterium tuberculosis methionine sulfoxide reductase A

Enzymatic reduction of the methylsulfinylxylofuranosyl (MSX) groups in lipoarabinomannan provides proof of the absolute configuration of MSX and a possible biochemical mechanism for oxidative protection in Mycobacterium tuberculosis.

Synthesis and in-vitro antibacterial activity of 5-substituted 1-methyl-4-nitro-1H-imidazoles

A series of 5-substituted 1-methyl-4-nitro-1H-imidazole derivatives were synthesized and evaluated for in-vitro antibacterial activity against a panel of microorganisms including Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, Enterobacter aerogenes, and Helicobacter pylori using conventional agar dilution method. Among the test compounds, 1-methyl-4-nitro-5-(phenylsulfonyl)-1H-imidazole was the most potent against Gram-positive bacteria, with a MIC value of < or =8 microg/mL. All compounds showed no significant activity against Gram-negative bacteria at concentrations < or =64 microg/mL. The MIC values against 15 clinical isolates of H. pylori indicated that compounds 10 and 11 were the most active compounds in this series in terms of inhibiting the growth of H. pylori (MIC = 2 microg/mL). It was also demonstrated that their corresponding activities were four times larger than that of metronidazole.

Synthesis, antimicrobial and antineoplastic activities for agelasine and agelasimine analogs with a beta-cyclocitral derived substituent

Agelasines and agelasimines are antimicrobial and cytotoxic purine derivatives isolated from marine sponges (Agelas sp.). We have synthesized structurally simplified analogs of these natural products starting from beta-cyclocitral. The novel compounds were found to be strong inhibitors of a wide variety of pathogenic microorganisms (incl. Mycobacterium tuberculosis) as well as cancer cell lines. The biological activities were generally in the same range as those previously found for the structurally more complex agelasines and agelasimines isolated in small amounts from natural sources. We also report for the first time that agelasine and agelasimine analogs inhibit growth of protozoa (Acanthamoeba castellanii and Acanthamoeba polyphaga). Acanthamoeba keratitis is an increasingly common and severe corneal infection, closely associated with contact lens wear.

New Hydrophobicity Constants of Substituents in Pyrazine Rings Derived from RP-HPLC Study

Pyrazine derivatives show a wide range of biological activities. 1-Pyrazin-2-ylethan-1-ones have served as food flavourants, and together with pyrazine-2-carbonitriles have been widely used as intermediates in the synthesis of various heterocyclic compounds. In our laboratory, substituted pyrazine-2-carbonitriles and 1-pyrazin-2-ylethan-1-ones have been used as intermediates for the preparation of potential antifungal and antimycobacterial drugs. Using established methods, a library of pyrazine derivatives was synthesized. Homolytic alkylation of commercially available pyrazine-2-carbonitrile yielded a series of 5-alkylpyrazine-2-carbonitriles which were converted into the corresponding 1-(5-alkylpyrazin-2-yl)ethan-1-ones (5-alkyl-2-acetylpyrazines) via the Grignard reaction. Homolytic acetylation of pyrazine-2-carbonitrile yielded 5-acetylpyrazine-2-carbonitrile. Using the same procedure, 3-acetyl-5-tert-butylpyrazine-2-carbonitrile was obtained with 5-tert-butylpyrazine-2-carbonitrile as a starting material. The hydrophobicity of the compounds was determined both experimentally (RP-HPLC) and by computation (CS ChemOffice Ultra version 9.0, ACD/LogP version 1.0 and ACD/LogP version 9.04), and both the approaches were compared. New hydrophobicity constants π based on experimental results were derived. These constants are markedly different from tabulated constants π valid for benzene rings, and can be widely used in estimating physicochemical properties of new biologically active pyrazines.

Substituted N-phenylpyrazine-2-carboxamides, their synthesis and evaluation as herbicides and abiotic elicitors

The condensation of substituted pyrazine-2-carboxylic acid chlorides with ring-substituted anilines yielded five substituted pyrazine-2-carboxylic acid amides. Thesynthesis, and analytical, lipophilicity and biological data of the newly synthesizedcompounds are presented in this paper. The photosynthesis inhibition, antialgal activityand the effect of a series of pyrazine derivatives as abiotic elicitors on the accumulation offlavonoids in a callus culture of Ononis arvensis (L.) were investigated. The most activeinhibitor of the oxygen evolution rate in spinach chloroplasts was 6-chloro-pyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2, IC(50) = 51.0 micromol.L(-1)). The highestreduction of chlorophyll content in Chlorella vulgaris was found for 5-tert-butyl-N-(4-chloro-3-methylphenyl)-pyrazine-2-carboxamide (3, IC(50) = 44.0 micromol.L(-1)). The maximalflavonoid production (about 900%) was reached after a twelve-hour elicitation processwith 6-chloropyrazine-2-carboxylic acid (3-iodo-4-methylphenyl)-amide (2).

The crystal structures of ornithine carbamoyltransferase from Mycobacterium tuberculosis and its ternary complex with carbamoyl phosphate and L-norvaline reveal the enzyme's catalytic mechanism

Mycobacterium tuberculosis ornithine carbamoyltransferase (Mtb OTC) catalyzes the sixth step in arginine biosynthesis; it produces citrulline from carbamoyl phosphate (CP) and ornithine (ORN). Here, we report the crystal structures of Mtb OTC in orthorhombic (form I) and hexagonal (form II) space groups. The molecules in form II are complexed with CP and l-norvaline (NVA); the latter is a competitive inhibitor of OTC. The asymmetric unit in form I contains a pseudo hexamer with 32 point group symmetry. The CP and NVA in form II induce a remarkable conformational change in the 80s and the 240s loops with the displacement of these loops towards the active site. The displacement of these loops is strikingly different from that seen in other OTC structures. In addition, the ligands induce a domain closure of 4.4 degrees in form II. Sequence comparison of active-site residues of Mtb OTC with several other OTCs of known structure reveals that they are virtually identical. The interactions involving the active-site residues of Mtb OTC with CP and NVA and a modeling study of ORN in the form II structure strongly rule out an earlier proposed mechanistic role of Cys264 in catalysis and suggest a possible mechanism for OTC. Our results strongly support the view that ORN with an already deprotonated N(epsilon) atom is the species that binds to the enzyme and that one of the phosphate oxygen atoms of CP is likely to be involved in accepting a proton from the doubly protonated N(epsilon) atom of ORN. We have interpreted this deprotonation as part of the collapse of the transition state of the reaction.

Synthesis, biological activity, and SAR of antimycobacterial 2- and 8-substituted 6-(2-furyl)-9-(p-methoxybenzyl)purines

A number of 6-(2-furyl)-9-(p-methoxybenzyl)purines carrying a variety of substituents in the 2- or 8-position have been synthesized and their ability to inhibit growth of Mycobacterium tuberculosis in vitro has been determined. It is demonstrated that sterical hindrance in the purine 8-position reduces activity and that C-8 should be unsubstituted. In the purine 2-position small, hydrophobic substituents are beneficial. The electronic properties of the 2-substituents appear to have only a minor influence on bioactivity. The compounds studied exhibit low toxicity toward mammalian cells (VERO cells) and are essentially inactive toward Staphylococcus aureus and Escherichia coli. The most active and selective antimycobacterial in the series detected to date is the novel 2-methyl-6-furyl-9-(p-methoxybenzyl)purine with MIC=0.20 microg/mL against M. tuberculosis and IC(50) against VERO cells >62.5 microg/mL. Also the novel 2-fluoro analog and the previously known 2-chloro compound, both with MIC=0.39 microg/mL, are highly interesting drug candidates.

Catalytic Asymmetric Synthesis of Phthioceranic Acid, a Heptamethyl-Branched Acid from Mycobacterium tuberculosis

The first total synthesis of phthioceranic acid (1) has been achieved by an iterative catalytic asymmetric 1,4-addition protocol. This method provides a robust and high-yielding route for the preparation of 1,3-oligomethyl (deoxypropionate) arrays. After the desired number of methyl groups has been introduced, these arrays can be further functionalized at both ends to polymethyl-substituted lipids such as phthioceranic acid, a heptamethyl-branched fatty acid from the virulence factor Sulfolipid-I (2), found in Mycobacterium tuberculosis.

Antimicrobial and cytotoxic activity of agelasine and agelasimine analogs

Agelasine and agelasimine derivatives with substantially less complicated terpenoid side chains compared to the naturally occurring compounds have been synthesized and their ability to inhibit growth of microorganisms and cancer cells has been studied. Compounds with excellent activity against cancer cell lines (MIC ca. 1 microM for the most potent compounds), including a drug resistant renal cell line, have been identified. Most compounds studied also exhibited broad spectrum antimicrobial activity including activity against Mycobacterium tuberculosis.

Indian medicinal plants as a source of antimycobacterial agents

It is estimated that one-third of the world's population is infected with tubercle bacillus and the problem of tuberculosis (TB) has been intensified due to HIV pandemic providing a large reservoir of highly susceptible individuals. Since no anti-TB drugs have been introduced in past 30 years, there is an urgent need to search for and develop new, effective and affordable anti-TB drugs. In this scenario, the plant kingdom with enormous chemical diversity may be looked as an important source of new anti-TB agents. Of 17,500 higher plant species occurring in India only about 365 species have been evaluated so far for antimycobacterial activity. The present review article describes the 255 (70% of 365) plant species from a wide range of families that have shown antimycobacterial activity. The species are enumerated in table format describing plant species and family, plant part used, type of extract and in vitro activity (MIC value), information on active compounds, if any, and uses in the ethnomedicine and Ayurveda. Interestingly, most of the plant species have shown strong positive ethnopharmacological correlation with the traditional knowledge. In addition, the recent in vitro screening methods for antimycobacterial activity are also described in brief. An attempt has been made to highlight the promising plant species for further investigation as leads for drug development.

Antitubercular Activity of Mushrooms (Basidiomycetes) and their Metabolites

Re-emergence of multi-drug resistant and HIV-associated tuberculosis justifies the search for new anti-TB agents. Mushrooms (Basidiomycetes) and their secondary metabolites are relatively little explored in this respect. A short review of antitubercular mushrooms and their active metabolites is presented here.

Natural product growth inhibitors of Mycobacterium tuberculosis

This review covers natural products (secondary metabolites) with reported growth inhibitory activity towards Mycobacterium tuberculosis or related organisms. Such compounds have been isolated from a variety of sources including terrestrial and marine plants and animals, and microorganisms, with the express intent of identifying novel scaffolds for the development of new antituberculosis agents. The literature from January 2003 to December 2005 (inclusive) is reviewed and 146 references to 353 compounds are cited. The compounds are presented in order of chemical type, namely lipids/fatty acids and simple aromatics, phenolics and quinones, peptides, alkaloids, terpenes (monoterpenoids, diterpenes, sesquiterpenes and triterpenes), steroids and miscellaneous structures.

Synthesis and antitubercular activity of substituted phenylmethyl- and pyridylmethyl amines

A total of 42 benzyl- and pyridylmethyl amines were synthesized either by reductive amination of aromatic/heteroaromatic aldehydes with amines or by conjugate addition of amines to the cinnamates followed by reduction of the ester group with lithium aluminium hydride to the respective propanolamines. All the synthesized compounds were evaluated against both avirulent and virulent strains of Mycobacterium tuberculosis. Many of the compounds exhibited MIC as low as 1.56microg/mL. Few of potent compounds were also evaluated against clinical isolates of MDR TB and found to be active at one or other concentrations with MIC as low as 3.12microg/mL.

Search of antitubercular activities in tetrahydroacridines: Synthesis and biological evaluation

A series of 9-substituted tetrahydroacridines were synthesized by nucleophilic substitution of chloro group with different nucleophiles in 9-chlorotetrahydroacridine (2). The latter could be obtained by POCl(3) mediated cyclization of the intermediate enamine, which in turn, was prepared by acid catalyzed condensation of anthranilic acid and cyclohexanone. Most of the compounds on antitubercular evaluation against M. tuberculosis H37 Rv and H37 Ra strains exhibited potent activities with MIC 6.125-0.78 microg/mL comparable to the standard drugs.

Determination of the Bound Conformation of a Competitive Nanomolar Inhibitor ofMycobacterium tuberculosis Type II Dehydroquinase by NMR Spectroscopy

The synergy between tuberculosis and the AIDS epidemic, along with the surge of multidrug-resistant isolates of M. tuberculosis, has reaffirmed tuberculosis as a primary public health threat. It is therefore necessary to discover new, safe, and more efficient antibiotics against this disease. On the other hand, mapping the dynamic interactions of inhibitors of a target protein can provide information for the development of more potent inhibitors and consequently, more potent potential drugs. In this context, the conformational binding of our previously reported nanomolar inhibitor of M. tuberculosis type II dehydroquinase, the 3-nitrophenyl derivative 1, was studied using saturation transfer difference (STD) and transferred NOESY experiments. These studies have shown that in the bound state, one conformation of those present in solution of the competitive nanomolar inhibitor 3-nitrophenyl derivative 1 is selected. In the bound conformation, the aromatic ring is slightly shifted from coplanarity, with the double bond and the nitro group of 1 oriented towards the double bond side.

Host–parasite interactions for virulence and resistance in a malaria model system

A rich body of theory on the evolution of virulence (disease severity) attempts to predict the conditions that cause parasites to harm their hosts, and a central assumption to many of these models is that the relative virulence of pathogen strains is stable across a range of host types. In contrast, a largely nonoverlapping body of theory on coevolution assumes that the fitness effects of parasites on hosts is not stable across host genotype, but instead depends on host genotype by parasite genotype interactions. If such genetic interactions largely determine virulence, it becomes difficult to predict the strength and direction of selection on virulence. In this study, we tested for host-by-parasite interactions in a medically relevant vertebrate disease model: the rodent malaria parasite Plasmodium chabaudi in laboratory mice. We found that parasite and particularly host main effects explained most of the variance in virulence (anaemia and weight loss), resistance (parasite burden) and transmission potential. Host-by-parasite interactions were of limited influence, but nevertheless had significant effects. This raises the possibility that host heterogeneity may affect the rate of any parasite response to selection on virulence. This study of rodent malaria is one of the first tests for host-by-parasite interactions in any vertebrate disease; host-by-parasite interactions typical of those assumed in coevolutionary models were present, but were by no means pervasive.

Synthesis, tuberculosis inhibitory activity, and SAR study of N-substituted-phenyl-1,2,3-triazole derivatives

The aim of this work was to describe the synthesis, the in vitro anti-Mycobacterium tuberculosis profile, and the structure-activity relationship (SAR) study of new N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a-l). The reactions of aromatic amine hydrochlorides with diazomalonaldehyde (1) produced several N-substituted-phenyl-1,2,3-triazole-4-carbaldehydes (3a-l) in moderate-to-good yields. In order to investigate the influence of the difluoromethylene group on the anti-Mycobacterium activity of these compounds, fluorination of triazoles with DAST converted the corresponding carbaldehyde compounds into new difluoromethyl derivatives (4a-l) in excellent yield. Characterization of all compounds was achieved by spectroscopic means and additional for 1-(4-methylphenyl)-1,2,3-triazole-4-carbaldehyde, 3k by X-ray crystallography. Compounds (3a-l) and (4a-l) have been screened for the inhibitory activity against Mycobacterium tuberculosis H37Rv strain (ATCC 27294) and all of them were able to inhibit the growth of the bacterium. Interestingly, 3a and 3k exhibited the best inhibition with MIC values of 2.5mug/mL, similar to pharmaceuticals currently used in the treatment of tuberculosis. Our SAR study indicated the importance of the hydrogen bond acceptor subunit (3a-l), the position in the aromatic ring, the planarity of triazole and phenyl rings in these compounds, and a correlation between the uniform HOMO coefficient distribution and the anti-tubercular activity. The significant activity of 3a and 3k pointed them as promising lead molecules for further synthetic and biological exploration.

Benzofuro[3,2-f][1]benzopyrans: A new class of antitubercular agents

Alkylation of 2-hydroxydibenzofuran with 3-chloro-3-methyl-1-butyne, followed by Claisen rearrangement, gave access to 3,3-dimethyl-3Hbenzofuro[3,2-f][1]-benzopyran. Several derivatives modified at the pyran 1,2-double bond were prepared, including the corresponding dihydro compound and (+/-)-cis-diol, which was converted into diacetate and cyclic carbonate upon acylation. Both 3,3-dimethyl-3Hbenzofuro[3,2-f][1]benzopyran and 1,2-dihydro-3,3-dimethyl-3Hbenzofuro[3,2-f][1]benzopyran displayed significant activities when tested against Mycobacterium tuberculosis H37Rv and Beijing strains, with MIC99 in the range of 1-10 microg/ml. Further biological studies demonstrated good activities against drug-resistant mycobacterial strains. These compounds appear as promising specific antitubercular agents, since they exhibited neither significant cytotoxicity against mammal cells, nor effect on the growth of various bacteria and fungi.

Mycobacterial synovitis caused by slow-growing nonchromogenic species: eighteen cases and a review of the literature

CONTEXT

Slow-growing nonchromogenic mycobacterial species are an infrequent cause of soft tissue infection. Because these organisms are rare, they are not often initially considered in the differential diagnosis of synovitis.

OBJECTIVE

To evaluate the clinical and pathologic characteristics of patients with synovitis resulting from slow-growing nonchromogenic mycobacterial species.

DESIGN

A 20-year retrospective review of records from The Methodist Hospital Microbiology Laboratory identified 18 culture-positive cases of synovitis that resulted from slow-growing nonchromogenic mycobacteria, including 14 caused by Mycobacterium avium complex, 1 caused by Mycobacterium malmoense, 1 caused by Mycobacterium haemophilum, and 2 caused by Mycobacterium nonchromogenicum isolates. In addition, a comprehensive literature search revealed an additional 48 cases of synovitis caused by slow-growing nonchromogenic mycobacteria.

RESULTS

The historic literature described the majority of the 48 patients as previously healthy, elderly individuals with a several-month history of monoarticular pain and swelling in the small joints of the upper extremity. In contrast, the current series demonstrated the probable role of multiple chronic coexisting medical conditions in promoting disease susceptibility. These patients were also unique in their significantly younger age distribution and diversity of infection sites. Histologic examination and direct acid-fast bacteria stains generally did not aid the diagnosis. Amputation was performed in 2 patients because of delayed identification of disease.

CONCLUSIONS

The current series demonstrates that difficult identification and infrequent occurrence cause these organisms to be overlooked by physicians and laboratory personnel. A heightened clinical suspicion for slow-growing nonchromogenic mycobacterial species is necessary when routine culture and histopathologic findings do not readily isolate an organism, or when the patient does not respond to antibiotic and anti-inflammatory treatment.

Synthesis and antimycobacterial activity of some alkyl [5-(nitroaryl)-1,3,4-thiadiazol-2-ylthio]propionates

Two series of 2- and 3-[5-(nitroaryl)-1,3,4-thiadiazol-2-ylthio, sulfinyl and sulfonyl] propionic acid alkyl esters were synthesized and screened for antituberculosis activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system. The MIC values for the compounds showing more than 90% inhibition were determined. The result of comparison between two groups of data exhibited that among the synthesized derivatives, the compound propyl 3-[5-(5-nitrothiophen-2-yl)-1,3,4-thiadiazol-2-ylthio]propionate was the most active one (MIC=1.56 microgml(-1)).

Synthesis and Biological Evaluation of (E)-3-(Nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones

The title (E)-(3-nitrophenyl)-1-(pyrazin-2-yl)prop-2-en-1-ones were prepared by the Claisen- Schmidt condensation of acetylpyrazines and 2-nitro-, 3-nitro- and 4-nitrobenzaldehyde in pyridine using diethylamine as the catalyst. The compounds were bioassayed for in vitro antifungal, antimycobacterial and photosynthesis-inhibiting activity. The high potency of (E)-1-(5-tert-butylpyrazin-2-yl)-3-(4-nitrophenyl)prop-2-en-1-one againstMycobacterium tuberculosis(MIC 0.78 μg/ml) and moderate activities of several compounds againstTrichophyton mentagrophytesandCandidaspp. do not support the assumption that phenolic groups are essential for antimycobacterial and antifungal activity of chalcones and their analogues. In fact, the nitro-substituted compounds were superior to the previously described hydroxylated congeners with antimycobacterial activity (MIC ≥ 12.5 μg/ml). The compounds also reduced chlorophyll content in green algaChlorella vulgaris, and some of them inhibited photosynthetic electron transport in spinach chloroplasts as well. The photosynthesis-inhibiting activity of nitro derivatives was lower than that of the corresponding hydroxylated analogues.

New Agents with Antimycobacterial Activity

In this paper, we report that a series of structurally simple a-halogenoacetamides show potent and excellent antimycobacterial activities against drug-sensitive Mycobacterium tuberculosis H(37)Rv and drug-resistant M. avium.

New perspectives on natural products in TB drug research

The challenge of discovering new, urgently needed anti-TB drugs from natural sources requires a truly interdisciplinary research. Cutting-edge mycobacteriology and innovative natural products chemistry tools have to be developed and employed in tandem, in order to meet these demands. The present review provides cross-linkage to the most recent literature on anti-TB active natural products and summarizes the recent developments in both fields and their potential to impact the early steps of the TB drug discovery process.

Synthesis and antitubercular activities of bis-glycosylated diamino alcohols

Conjugate addition of diamines to glycosyl olefinic esters 1a and 1b followed by reduction of resulting bis-glycosyl beta-amino esters (2-7 and 14-19) with lithium aluminium hydride led to the respective glycosyl amino alcohols (8-13 and 20-25) in moderate to good yields. All the compounds were evaluated for antitubercular activity against Mycobacterium tuberculosis H(37)Ra and H(37)Rv. Few of the compounds exhibited antitubercular activity with MIC as low as 6.25-3.12microg/mL in virulent and avirulent strains. Compound 13 was found to be active against MDR strain and showed mild protection in mice.

An efficient synthesis of aryloxyphenyl cyclopropyl methanones: a new class of anti-mycobacterial agents

An efficient, high yield and one-pot synthesis of phenyl cyclopropyl methanones by reaction of different aryl alcohols with 4'-fluoro-4-chloro-butyrophenone in THF/DMF in the presence of NaH/TBAB is reported. Most of the methanones were further reduced to respective alcohols or methylenes. All the compounds were evaluated for their anti-tubercular activities against M. tuberculosis H37Rv in vitro displaying MICs ranging from 25 to 3.125 microg/mL. The most active compounds showed activity against MDR strains and two of them (14 and 16) showed marginal enhancement of MST in mice.