Novel 1,2,3-Triazole Derivatives for Use against Mycobacterium tuberculosis H37Rv (ATCC 27294) Strain

1-Phenyl-1H- and 2-phenyl-2H-1,2,3-triazol derivatives: design, synthesis and inhibitory effect on alpha-glycosidases

Due to aging and increasingly overweight in human population, the incidence of non-insulin dependent diabetes mellitus (NIDDM or Type 2 DM) is increasing considerably. Therefore, searching for new α-glycosidase inhibitors (GIs) capable of slowing down carbohydrate assimilation by humans is an important strategy towards control of NIDDM. In this report, we disclose the search for new easily accessible synthetic triazoles as anti-diabetic compounds. Two series of non-glycosid triazoles were synthesized (series A and B) and screened against baker's yeast α-glucosidase (MAL12) and porcine pancreatic α-amylase activity (PPA). Of the 60 compounds tested at 500 μM, were considered hits (≥60% inhibition) six triazoles against MAL12 and three against PPA, with the inhibition reaching up to 99.4% on MAL12 and 88.6% on PPA. The IC₅₀ values were calculated for both enzymes and ranged from 54 to 482 μM for MAL12 and 145 to 282 μM for PPA. These results demonstrated the potential activity of simple and non-glycosidic triazoles as an important novel class of GIs for the development of drugs to treat Type 2 DM.

The eradication of leprosy: molecular modeling techniques for novel drug discovery

INTRODUCTION

Leprosy is a slowly progressing bacterial infection caused by Mycobacterium leprae. The World Health Organization recommended multidrug therapy (MDT) which is extremely effective and halts the progress of the disease. Even though the objective of eliminating leprosy as a public health problem has been achieved successfully, leprosy is not yet eradicated. Furthermore, the long-term use of MDT results in single- and multidrug resistance. Therefore, there is still a need for new drug discovery for leprosy.

AREAS COVERED

The authors explain the importance of discovery of new drug to leprosy and the significance of homology modeling to drug discovery. This review highlights the principle steps, applications, and the resources of homology modeling. Finally, the authors emphasize the application of different structure-based drug design (SBDD) approaches to design novel therapeutics for leprosy.

EXPERT OPINION

MDT has proved to be effective in controlling infection, with prevalence of leprosy now predominantly isolated to the developing countries. The emergence of single- and multidrug-resistant strains of M. leprae has, however, provided some concern with the need for newer antibacterial agents. Drug resistance can be overcome by multi-targeted therapy. SBDD approaches, which reported many successful drugs, depend predominantly on the three-dimensional (3D) structure of drug targets. As of 2013, only very few experimental structures are available for M. leprae proteins. Hence, SBDD, in leprosy research, relies heavily on homology modeling to predict the 3D structure of drug targets and to design better therapeutics.

Resistance in tuberculosis: what do we know and where can we go?

Tuberculosis (TB) has become a worldwide threat, mainly due to the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis (Mtb). This mini-review is focused on the various mechanisms of resistance to the currently available anti-TB drugs and provides perspective on novel strategies and lead scaffolds/compounds aimed at inhibiting/overcoming these resistance mechanisms.

Synthesis and evaluation of α-ketotriazoles and α,β-diketotriazoles as inhibitors of Mycobacterium tuberculosis

Two series of α-ketotriazole and α,β-diketotriazole derivatives were synthesized and evaluated for antitubercular and cytotoxic activities. Among them, two α,β-diketotriazole compounds, 6b and 9b, exhibited good activities (minimum inhibitory concentration = 7.6 μM and 6.9 μM, respectively) on Mycobacterium tuberculosis and multi-drug resistant M. tuberculosis strains and presented no cytotoxicity (IC₅₀ > 50 μM) on colorectal cancer HCT116 and normal fibroblast GM637H cell lines. These two compounds represent promising leads for further optimization.

Antituberculosis thiophenes define a requirement for Pks13 in mycolic acid biosynthesis

We report a new class of thiophene (TP) compounds that kill Mycobacterium tuberculosis (Mtb) by the novel mechanism of Pks13 inhibition. An F79S mutation near the catalytic Ser-55 site in Pks13 conferred TP-resistance in Mtb. Over-expression of wild-type pks13 resulted in TP-resistance and over-expression of the F79S pks13 mutant conferred high-level resistance. In vitro, TP inhibited fatty acyl-AMP loading onto Pks13. TP inhibited mycolic acid biosynthesis in wild-type Mtb, but to a much lesser extent in TP-resistant Mtb. TP treatment was bactericidal and equivalent to the first-line drug isoniazid, but it was less likely to permit emergent resistance. Combined isoniazid and TP treatment exhibited sterilizing activity. Computational-docking identified a possible TP-binding groove within the Pks13 ACP domain. This study confirms that Mtb Pks13 is required for mycolic acid biosynthesis, validates it as a druggable target and demonstrates the therapeutic potential of simultaneously inhibiting multiple targets in the same biosynthetic pathway.

Synthesis and bioevaluation of some new isoniazid derivatives

The aim of the study was to synthesize some new compounds with potential anti-tuberculosis activity, containing isoniazid and α,β-unsaturated thiocinnamamide-like thioamides as precursors. The obtained derivatives were evaluated regarding their biological activity (antioxidant and antibacterial), as well as their influence on the eukaryotic cell cycle. The results suggested that the newly obtained derivatives of isoniazid exhibited different biological activities, depending on their structure; thus, the most active compound in terms of anti-oxidant and anti-Mycobacterium tuberculosis effects proved to be the isonicotinic acid N'-(1-amino-1-mercapto-3-phenyl-propen-1-yl)-hydrazide. This compound also increased the expression of NAT1 and NAT2 genes, which are implicated in the metabolism of the isoniazid, demonstrating that it could be rapidly metabolized, and thus well tolerated. The largest spectrum of antibacterial activity (excluding M. tuberculosis) was noticed for the isonicotinic acid N'-[1-amino-1-mercapto-3-(p-chloro-phenyl)-propen-1-yl]-hydrazide, which was also the most cytotoxic, especially at high concentrations, although not significantly affecting the cellular cycle phases. The obtained results showed that the new derivatives could represent potential candidates for the treatment of M. tuberculosis infections, but further research is needed in order to improve their pharmacological properties, by increasing their antimicrobial activity and reducing the risk of side-effects.

Nitroxides attenuate carrageenan-induced inflammation in rat paws by reducing neutrophil infiltration and the resulting myeloperoxidase-mediated damage

Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) and other cyclic nitroxides have been shown to inhibit the chlorinating activity of myeloperoxidase (MPO) in vitro and in cells. To examine whether nitroxides inhibit MPO activity in vivo we selected acute carrageenan-induced inflammation on the rat paw as a model. Tempol and three more hydrophobic 4-substituted derivatives (4-azido, 4-benzenesulfonyl, and 4-(4-phenyl-1H-1,2,3-triazol-1-yl)) were synthesized, and their ability to inhibit the in vitro chlorinating activity of MPO and carrageenan-induced inflammation in rat paws was evaluated. All of the tested nitroxides inhibited the chlorinating activity of MPO in vitro with similar IC(50) values (between 1.5 and 1.8 μM). In vivo, the attenuation of carrageenan-induced inflammation showed some correlation with the lipophilicity of the nitroxide at early time points but the differences in the effects were small (<2-fold) compared with the differences in lipophilicity (>200-fold). No inhibition of MPO activity in vivo was evident because the levels of MPO activity in rat paws correlated with the levels of MPO protein. Likewise, paw edema, levels of nitrated and oxidized proteins, and levels of plasma exudation correlated with the levels of MPO protein in the paws of the animals that were untreated or treated with the nitroxides. The effects of the nitroxides in vivo were compared with those of 4-aminobenzoic hydrazide and of colchicine. Taken together, the results indicate that nitroxides attenuate carrageenan-induced inflammation mainly by reducing neutrophil migration and the resulting MPO-mediated damage. Accordingly, tempol was shown to inhibit rat neutrophil migration in vitro.

Triazolbenzo[d]thiazoles: efficient synthesis and biological evaluation as neuroprotective agents

A number of (1H-1,2,3-triazol-1-yl)benzo[d]thiazoles were synthesized utilizing a versatile Cu-catalyzed azide-alkyne click reaction (CuAAC) on tautomeric benzo[4,5]thiazolo[3,2-d]tetrazole (1) and 2-azidobenzo[d]thiazole (2) starting materials. Moreover, one of the resulting products of this investigation, triazolbenzo[d]thiazole 22, was found to possess significant neuroprotective activity in human neuroblastoma (SH-SY5Y) cells.

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.

[1-(3-Chloro-phen-yl)-1H-1,2,3-triazol-4-yl]methanol hemihydrate

The asymmetric unit of the title hydrate, C(9)H(8)ClN(3)O·0.5H(2)O, comprises two independent 1,2,3-triazole mol-ecules and a water mol-ecule of crystallization. The dihedral angles between the six- and five-membered rings in the 1,2,3-triazole mol-ecules are 12.71 (19) and 17.3 (2)°. The most significant different between them is found in the relative orientations of the terminal CH(2)OH groups with one being close to perpendicular to the five-membered ring [N-C-C-O torsion angle = 82.2 (5)°], while in the other mol-ecule, a notable deviation from a perpendicular disposition is found [torsion angle = -60.3 (5)°]. Supra-molecular chains feature in the crystal packing sustained by O-H⋯(O,N) inter-actions along the a-axis direction. The chains are connected via C-H⋯N inter-actions and the resultant layers stack along the b axis.