Hit-to-lead optimization of novel 2-alkylaminomethylquinoline derivatives as anti-chagas agents.

Chagas disease is one of the main neglected diseases in the world, being endemic in 21 countries of Latin America. This disease has become a global health problem due to migration of infected people non-endemic countries. Even though this disease affects millions of people, only two drugs are approved for its treatment, benznidazole and nifurtimox, and both have several limitations. We have previously reported the synthesis and biological activity against T. cruzi of polysubstituted quinolines analogous to natural products. Herein, we present the synthesis of rationally-based novel analogous of this family of compounds. All the evaluated compounds presented trypanocidal activity. Three of them (6, 7 and 10) stand out for their selectivity indexes. Ethyl 2-((4-benzyl-1,4-diazepan-1-yl)methyl)-6-chloro-4-phenylquinoline-3-carboxylate (compound 10) was found to display anti-parasite activity, presenting the highest selectivity index. Apart from controlling in vivo the parasitemia levels, compound 10 was able to prevent tissue inflammation, a key factor to prevent the progression to chronic chagasic cardiomyopathy. The therapeutic effects of compound 10 are promising and suggest a new possibility to treat this disease.

Microwave-assisted Synthesis of 2-Styrylquinoline-4-carboxylic Acids as Antitubercular Agents.

BACKGROUND: Many 2-substituted quinolines and especially 2-arylvinyl derivatives isolated from plants or prepared by synthesis have been designed from ethnopharmacological studies. OBJECTIVE: In order to explore new aspects of the structure-antituberculosis activity relationship, a series of styrylquinoline derivatives was prepared. METHOD: A series of styrylquinoline derivatives was prepared from quinaldic acid and a variety of arylbenzaldehydes under eco-friendly conditions via Knoevenagel reaction and trifluoroacetic acid (TFA) as catalyst. RESULTS: The products were obtained in short reaction times and good yields and were evaluated for growth inhibitory activity towards Mycobacterium tuberculosis H37Rv (Mtb) through the National Institute of Allergy and Infectious Diseases (NIAID, USA). CONCLUSION: Three compounds had activity under aerobic conditions.

gem-Diol and Hemiacetal Forms in Formylpyridine and Vitamin-B6-Related Compounds: Solid-State NMR and Single-Crystal X-ray Diffraction Studies.

The gem-diol moieties of organic compounds are rarely isolated or even studied in the solid state. Here, liquid- and solid-state NMR, together with single-crystal X-ray diffraction studies, were used to show different strategies to favor the gem-diol or carbonyl moieties and to isolate hemiacetal structures in formylpyridine and vitamin-B6-related compounds. The change in position of the carbonyl group in pyridine compounds had a clear and direct effect on the hydration, which was enhanced by trifluoroacetic acid addition. Because of their biochemical importance, vitamin-B6-related compounds were studied with emphasis on the elucidation of the gem-diol, cyclic hemiacetal or carbonyl structures that can be obtained in different experimental conditions. In particular, new racemic mixtures for the cyclic hemiacetal structure from pyridoxal are reported in trifluoroacetate and hydrochloride derivatives.

HmuS and HmuQ of Ensifer/Sinorhizobium meliloti degrade heme in vitro and participate in heme metabolism in vivo.

Ensifer meliloti is a nitrogen-fixing symbiont of the alfalfa legume able to use heme as an iron source. The transport mechanism involved in heme acquisition in E. meliloti has been identified and characterized, but the fate of heme once inside the cell is not known. In silico analysis of E. meliloti 1021 genome revealed no canonical heme oxygenases although two genes encoding putative heme degrading enzymes, smc01518 and hmuS, were identified. SMc01518 is similar to HmuQ of Bradyrhizobium japonicum, which is weakly homologous to the Staphylococcus aureus IsdG heme-degrading monooxygenase, whereas HmuS is homolog to Pseudomonas aeruginosa PhuS, a protein reported as a heme chaperone and as a heme degrading enzyme. Recombinant HmuQ and HmuS were able to bind hemin with a 1:1 stoichiometry and displayed a Kd value of 5 and 4 µM, respectively. HmuS degrades heme in vitro to the biliverdin isomers IX-ß and IX-δ in an equimolar ratio. The HmuQ recombinant protein degrades heme to biliverdin IX-δ only. Additionally, in this work we demonstrate that humS and hmuQ gene expression is regulated by iron and heme in a RirA dependent manner and that both proteins are involved in heme metabolism in E. meliloti in vivo.

Synthesis and evaluation of 2-(1H-indol-3-yl)-4-phenylquinolines as inhibitors of cholesterol esterase.

A series of 2-(substituted) phenyl and 2-indolyl quinoline derivatives (10a-l) was synthesized by an efficient microwave-assisted, trifluoroacetic acid-catalyzed, solvent-free method. Evaluation of the inhibitory activity led to the identification of two quinoline inhibitors of cholesterol esterase. 2-(1H-Indol-3-yl)-6-nitro-4-phenylquinoline (10l; IC50=1.98µM) was characterized as a mixed-type inhibitor with a pronounced competitive binding mode.

Design, synthesis and evaluation of acridine and fused-quinoline derivatives as potential anti-tuberculosis agents.

The synthesis of twelve acridine and polycyclic acridine derivatives prepared via the Friedländer reaction is described. The one-pot reactions of 2-amino-5-chloro or 5-nitro-benzophenones and a variety of cyclanones and indanones were carried out in a MW oven under TFA catalysis in good yields. The products were designed according natural antituberculosis products and were evaluated for growth inhibitory activity towards Mycobacterium tuberculosis H37Rv (Mtb) through the National Institute of Allergy and Infectious Diseases (NIAID, USA). Three of them underwent additional testings. The cyclopenta[b]quinoline derivative 9 and the acridine derivative 13 showed remarkable MIC values against the rifampin resistant strain. The former exhibited bactericidal activity at 50 µg/mL, its intracellular activity is similar to rifampin and it was not cytotoxic at low concentrations so it can be considered a new lead compound.

Synthesis, trypanocidal activity and molecular modeling studies of 2-alkylaminomethylquinoline derivatives.

Research and development of new drugs effective in the treatment of Trypanosoma cruzi infections are a real need for the 16 million people infected in the Americas. In a previous work, a quinoline derivative substituted by a 2-piperidylmethyl moiety showed to be active against Chagas disease and was considered a lead compound for further optimization. A series of ten analogous derivatives were tested against epimastigotes as a first approach. In view of their promising results, six of them were evaluated against the blood and intracellular replicative forms of the parasite in humans. Among them, compound 12 which possesses a 6-acetamidohexylamino substituent showed remarkable improvement in activity against epimastigotes, trypomastigotes and amastigotes compared with the structure lead, as well as a good selectivity index for the two parasite stages present in humans. In addition, treatment of infected mice with compound 12 induced a significant reduction in parasitemia compared with non-treated mice. Molecular modeling studies were performed by computational methods in order to elucidate the factors determining these experimental bioactivities.

NMR characterization of hydrate and aldehyde forms of imidazole-2-carboxaldehyde and derivatives.

The existence and stability of the aldehyde-hydrate form of imidazole-2-carboxaldehyde (4) were studied using FTIR together with solution- and solid-state NMR experiments. The results allowed us to conclude that the hydrate form was stable and precipitated at pH = 8.0 and that the aldehyde form was isolated at pH = 6.5 and 9.5. Moreover, the presence of the aldehyde-hydrate form was studied through NMR experiments in D(2)O at both alkaline and acidic pH. In addition, the tautomeric forms of the 2-substituted imidazole compounds were also analyzed to investigate the influence of the hybridization on the carbon adjacent to the imidazole ring, by (13)C NMR in DMSO-d(6), acetone-d(6), and CDCl(3). The presence of the syn- and anti-isomers of oxime 8 obtained from 4 were characterized by solid-state NMR and variable-temperature NMR experiments in acetone-d(6).

Isoporphyrin intermediate in heme oxygenase catalysis. Oxidation of alpha-meso-phenylheme.

Human heme oxygenase-1 (hHO-1) catalyzes the O2- and NADPH-dependent oxidation of heme to biliverdin, CO, and free iron. The first step involves regiospecific insertion of an oxygen atom at the alpha-meso carbon by a ferric hydroperoxide and is predicted to proceed via an isoporphyrin pi-cation intermediate. Here we report spectroscopic detection of a transient intermediate during oxidation by hHO-1 of alpha-meso-phenylheme-IX, alpha-meso-(p-methylphenyl)-mesoheme-III, and alpha-meso-(p-trifluoromethylphenyl)-mesoheme-III. In agreement with previous experiments (Wang, J., Niemevz, F., Lad, L., Huang, L., Alvarez, D. E., Buldain, G., Poulos, T. L., and Ortiz de Montellano, P. R. (2004) J. Biol. Chem. 279, 42593-42604), only the alpha-biliverdin isomer is produced with concomitant formation of the corresponding benzoic acid. The transient intermediate observed in the NADPH-P450 reductase-catalyzed reaction accumulated when the reaction was supported by H2O2 and exhibited the absorption maxima at 435 and 930 nm characteristic of an isoporphyrin. Product analysis by reversed phase high performance liquid chromatography and liquid chromatography electrospray ionization mass spectrometry of the product generated with H2O2 identified it as an isoporphyrin that, on quenching, decayed to benzoylbiliverdin. In the presence of H218O2, one labeled oxygen atom was incorporated into these products. The hHO-1-isoporphyrin complexes were found to have half-lives of 1.7 and 2.4 h for the p-trifluoromethyl- and p-methyl-substituted phenylhemes, respectively. The addition of NADPH-P450 reductase to the H2O2-generated hHO-1-isoporphyrin complex produced alpha-biliverdin, confirming its role as a reaction intermediate. Identification of an isoporphyrin intermediate in the catalytic sequence of hHO-1, the first such intermediate observed in hemoprotein catalysis, completes our understanding of the critical first step of heme oxidation.

Human heme oxygenase oxidation of 5- and 15-phenylhemes.

Human heme oxygenase-1 (hHO-1) catalyzes the O2-dependent oxidation of heme to biliverdin, CO, and free iron. Previous work indicated that electrophilic addition of the terminal oxygen of the ferric hydroperoxo complex to the alpha-meso-carbon gives 5-hydroxyheme. Earlier efforts to block this reaction with a 5-methyl substituent failed, as the reaction still gave biliverdin IXalpha. Surprisingly, a 15-methyl substituent caused exclusive cleavage at the gamma-meso-rather than at the normal, unsubstituted alpha-meso-carbon. No CO was formed in these reactions, but the fragment cleaved from the porphyrin eluded identification. We report here that hHO-1 cleaves 5-phenylheme to biliverdin IXalpha and oxidizes 15-phenylheme at the alpha-meso position to give 10-phenylbiliverdin IXalpha. The fragment extruded in the oxidation of 5-phenylheme is benzoic acid, one oxygen of which comes from O2 and the other from water. The 2.29- and 2.11-A crystal structures of the hHO-1 complexes with 1- and 15-phenylheme, respectively, show clear electron density for both the 5- and 15-phenyl rings in both molecules of the asymmetric unit. The overall structure of 15-phenylheme-hHO-1 is similar to that of heme-hHO-1 except for small changes in distal residues 141-150 and in the proximal Lys18 and Lys22. In the 5-phenylheme-hHO-1 structure, the phenyl-substituted heme occupies the same position as heme in the heme-HO-1 complex but the 5-phenyl substituent disrupts the rigid hydrophobic wall of residues Met34, Phe214, and residues 26-42 near the alpha-meso carbon. The results provide independent support for an electrophilic oxidation mechanism and support a role for stereochemical control of the reaction regiospecificity.

Síntesis y control de tecnecio-99m-etilendicisteína: ensayo en seres humanos / Synthesis and control of thecnetium-99m-ethylenedicysteine: assays in humans beens

La L, L-etilendicisteína (L,L-EC) se sintetizó de acuerdo al método de P. Blondeau y colaboradores, con las modificaciones introducidas por R.F.Schneider. Se comprobó su pureza por punto de fusión, espectroscopia de masa, espectroscopia infrarroja, resonancia magnética nuclear y composición centesimal. Se realizaron estudios farmacológicos, esterilidad, apirogenicidad, toxicidad y distribución biológica de animales. La L,L-EC marcado con 99mTc se controló por cromatografía en papel e ITLC-SG. Se inyectó en seres humanos voluntarios normales y con patología renal 55,5-111,0 MBq(1,5-3,0 mCi), realizándose el estudio correspondiente

Síntesis y control de tecnecio-99m-etilendicisteína: ensayo en seres humanos / Synthesis and control of thecnetium-99m-ethylenedicysteine: assays in humans beens

La L, L-etilendicisteína (L,L-EC) se sintetizó de acuerdo al método de P. Blondeau y colaboradores, con las modificaciones introducidas por R.F.Schneider. Se comprobó su pureza por punto de fusión, espectroscopia de masa, espectroscopia infrarroja, resonancia magnética nuclear y composición centesimal. Se realizaron estudios farmacológicos, esterilidad, apirogenicidad, toxicidad y distribución biológica de animales. La L,L-EC marcado con 99mTc se controló por cromatografía en papel e ITLC-SG. Se inyectó en seres humanos voluntarios normales y con patología renal 55,5-111,0 MBq(1,5-3,0 mCi), realizándose el estudio correspondiente