In vitro evaluation of new 4-thiazolidinones on invasion and growth of Toxoplasma gondii.

Treatments for toxoplasmosis such as pyrimethamine have shown numerous side effects. It has been reported that the likelihood of relapse associated with pyrimethamine-based therapy in patients with HIV and toxoplasmic encephalitis (TE) can have significant implications, even for patients who often develop new lesions in areas of the brain previously free of infection. This led us to research for new agents against Toxoplasma gondii. Recent findings have shown the potent biological activity of 4-thiazolidinones. We proposed to design and synthesize a new series of 2-hydrazono-4-thiazolidinones derivatives to evaluate the in vitro growth inhibition effect on T. gondii. The growth rates of T. gondii tachyzoites in Human Foreskin Fibroblast (HFF) cell culture were identified by two in vitro methodologies. The first one was by fluorescence in which green fluorescent RH parasites and cherry-red fluorescent ME49 parasites were used. The second one was a colorimetric methodology using ß-Gal parasites of the RH strain constitutively expressing the enzyme beta-galactosidase. The 4-thiazolidinone derivatives 1B, 2B and 3B showed growth inhibition at the same level of Pyrimethamine. These compounds showed IC50 values of 1B (0.468-0.952 µM), 2B (0.204-0.349 µM) and 3B (0.661-1.015 µM) against T. gondii. As a measure of cytotoxicity the compounds showed a TD50 values of: 1B (60 µM), 2B (206 µM) and 3B (125 µM). The in vitro assays and molecular modeling results suggest that these compounds could act as possible inhibitors of the Calcium-Dependent Protein Kinase 1 of T. gondii. Further, our results support the fact that of combining appropriate detection technologies, combinatorial chemistry and computational biology is a good strategy for efficient drug discovery. These compounds merit in vivo analysis for anti-parasitic drug detection.

Protein targets of thiazolidinone derivatives in Toxoplasma gondii and insights into their binding to ROP18.

BACKGROUND: Thiazolidinone derivatives show inhibitory activity (IC50) against the Toxoplasma gondii parasite, as well as high selectivity with high therapeutic index. To disclose the target proteins of the thiazolidinone core in this parasite, we explored in silico the active sites of different T. gondii proteins and estimated the binding-free energy of reported thiazolidinone molecules with inhibitory effect on invasion and replication of the parasite inside host cells. This enabled us to describe some of the most suitable structural characteristics to design a compound derived from the thiazolidinone core. RESULTS: The best binding affinity was observed in the active site of kinase proteins, we selected the active site of the T. gondii ROP18 kinase, because it is an important factor for the virulence and survival of the parasite. We present the possible effect of a derivative of thiazolidinone core in the active site of T. gondii ROP18 and described some characteristics of substituent groups that could improve the affinity and specificity of compounds derived from the thiazolidinone core against T. gondii. CONCLUSIONS: The results of our study suggest that compounds derived from the thiazolidinone core have a preference for protein kinases of T. gondii, being promising compounds for the development of new drugs with potential anti-toxoplasmosis activity. Our findings highlight the importance of use computational studies for the understanding of the action mechanism of compounds with biological activity.

Octyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylate: complex sheets built from N-H···N, C-H···N and C-H···O hydrogen bonds.

In the title compound, C29H35ClN4O2, the bond lengths provide evidence for aromatic delocalization in the pyrazole ring but bond fixation in the fused imidazole ring, and the octyl chain is folded, rather than adopting an all-trans chain-extended conformation. A combination of N-H···N, C-H···N and C-H···O hydrogen bonds links the molecules into sheets, in which the hydrogen bonds occupy the central layer with the tert-butyl and octyl groups arranged on either side, such that the closest contacts between adjacent sheets involve only the octyl groups. Comparisons are made with the supramolecular assembly in some simpler analogues.

Four related esters: two 4-(aroylhydrazinyl)-3-nitrobenzoates and two 3-aryl-1,2,4-benzotriazine-6-carboxylates.

The molecules of both methyl 4-[2-(4-chlorobenzoyl)hydrazinyl]-3-nitrobenzoate, C15H12ClN3O5, (I), and methyl 4-[2-(2-fluorobenzoyl)hydrazinyl]-3-nitrobenzoate, C15H12FN3O5, (II), contain an intramolecular N-H···O hydrogen bond, and both show electronic polarization in the nitrated aryl ring. In both compounds, molecules are linked by a combination of N-H···O and C-H···O hydrogen bonds to form sheets, which are built from R4(3)(18) rings in (I) and from R4(4)(28) rings in (II). In each of methyl 3-phenyl-1,2,4-benzotriazine-6-carboxylate, C15H11N3O2, (III), and methyl 3-(4-methylphenyl)-1,2,4-benzotriazine-6-carboxylate, C16H13N3O2, (IV), the benzotriazine unit shows naphthalene-type delocalization. There are no hydrogen bonds in the structures of compounds (III) and (IV), but in both compounds, the molecules are linked into chains by π-π stacking interactions involving the benzotriazine units. The mechanism of chain formation is the same in both (III) and (IV), and the different orientations of the two chains can be related to the approximate relationship between the unit-cell metrics for (III) and (IV).

Hydrogen-bonded sheet structures in methyl 4-(4-chloroanilino)-3-nitrobenzoate and methyl 1-benzyl-2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylate.

In methyl 4-(4-chloroanilino)-3-nitrobenzoate, C(14)H(11)ClN(2)O(4), (I), there is an intramolecular N-H...O hydrogen bond and the intramolecular distances provide evidence for electronic polarization of the o-quinonoid type. The molecules are linked into sheets built from N-H...O, C-H...O and C-H...π(arene) hydrogen bonds, together with an aromatic π-π stacking interaction. The molecules of methyl 1-benzyl-2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylate, C(22)H(17)ClN(2)O(2), (II), are also linked into sheets, this time by a combination of C-H...π(arene) hydrogen bonds and aromatic π-π stacking interactions.

Synthesis of 3-aryl-1,2,4-benzotriazines via intramolecular cyclization of solid-supported o-hydrazidoanilines.

An efficient solid-phase protocol for the rapid generation of libraries of biologically promising 1,2,4-benzotriazines, including amino acid-derived components, is described.

Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential antitumor agents.

Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d]imidazole-5-carboxylates 11 were synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (S(N)Ar) and a solvent free approach as key steps for the formation of the desired products. Structure of intermediates and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI(50) range of 1.15-7.33 µM and 0.167-7.59 µM, respectively, and suitable LC(50) with values greater than 100 µM.

Methyl 2-(4-bromophenyl)-1-(5-tert-butyl-1H-pyrazol-3-yl)-1H-benzimidazole-5-carboxylate: a hydrogen-bonded chain of edge-fused centrosymmetric rings.

In the title compound, C(22)H(21)BrN(4)O(2), the imidazole and pyrazole rings are almost orthogonal to each other, but the ester unit is effectively coplanar with the adjacent aryl rings. The molecules are linked into a chain of edge-fused centrosymmetric rings by a combination of N-H···O and C-H···π(arene) hydrogen bonds.

Methyl 4-[(1-acetyl-3-tert-butyl-1H-pyrazol-5-yl)amino]-3-nitrobenzoate.

In the molecule of the title compound, C(17)H(20)N(4)O(5), there are two intramolecular N-H···O hydrogen bonds having amidic and nitro-group O atoms as the acceptors and together forming a three-centre N-H···(O)(2) system. These interactions appear to play an important role in controlling the relative orientation of the pyrazole and aryl rings. The bond distances provide evidence for some polarization of the electronic structure. Molecules are linked into simple chains by a single C-H···O hydrogen bond.