Hugo Cerecetto

Pharmacological Properties of Indazole Derivatives: Recent Developments

The chemistry of indazole and its N-oxide derivatives is very well-known. Indazole derivatives were extensively studied as bioactive compounds, such as anti-aggregatory and vasorelaxant activity by NO release and increase of cGMP levels and anticancer effects, antimicrobial and antiparasitic properties, among others. Recently, the research and development in the medicinal chemistry of these systems have produced compounds with contraceptive activities for men, for the treatment of osteoporosis, inflammatory disorders and neurodegenerative diseases. On the other hand, indazole N-oxide derivatives were poorly studied as bioactive compounds, but recently compounds with antiparasitic properties were produced. In this presentation, recent developments in the chemistry and medicinal chemistry of indazole and its N-oxide derivatives will be reviewed.

Pharmacological Properties of Furoxans and Benzofuroxans: Recent Developments

The chemistry of furoxans (1, 2, 5-oxadiazole-2-oxides) and benzofuroxans (benzo[1, 2-c]1, 2, 5-oxadiazole-1-oxides) is very well known. These systems are widely used in organic chemistry as intermediate compounds for the synthesis of numerous heterocycles. In the other hand, furoxan and benzofuroxan derivatives were extensively studied as bioactive compounds. They possess remarkable biological activities, such as anti-microbial and anti-parasitic properties, mutagenic, immunosuppressive and anticancer effects, anti-aggregating and vasorelaxant activity, among others. In some cases, molecular mode of action was proposed. Recently, the research and development in the medicinal chemistry of these systems have produced hybrid compounds in which furoxan or benzofuroxan moieties together with a classical drug moieties are present in a single molecule. So, new anti-ulcer drugs, calcium channel modulators and vasodilator derivatives were described and they are currently in study. In this presentation recent developments in the medicinal chemistry of furoxans and benzofuroxans will be reviewed.

Synthesis and antitrypanosomal evaluation of E-isomers of 5-nitro-2-furaldehyde and 5-nitrothiophene-2-carboxaldehyde semicarbazone derivatives. Structure-activity relationships.

Several novel semicarbazone derivatives were prepared from 5-nitro-2-furaldehyde or 5-nitrothiophene-2-carboxaldehyde and semicarbazides bearing a spermidine-mimetic moiety. All derivatives presented the E-configuration, as determined by NMR-NOE experiments. These compounds were tested in vitro as potential antitrypanosomal agents, and some of them, together with the parent compounds, 5-nitro-2-furaldehyde and 5-nitrothiophene-2-carboxaldehyde semicarbazone derivatives, were also evaluated in vivo using infected mice. Structure-activity relationship studies were carried out using voltammetric response and lipophilic-hydrophilic balance as parameters. Two of the compounds (1 and 3) displayed the highest in vivo activity. A correlation was found between lipophilic-hydrophilic properties and trypanocidal activity, high R(M) values being associated with low in vivo effects.

Synthesis, trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazones, designed as cruzain inhibitors candidates

In this paper, we report the structural design, synthesis, trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazone (NAH) derivatives, planned as cruzain inhibitors candidates, a cysteine protease essential for the survival of Trypanosoma cruzi within the host cell. The salicylaldehyde N-acylhydrazones 7a and 8a presented IC(50) values of the same magnitude order than the standard drug nifurtimox (Nfx), when tested in vitro against epimastigote forms of Trypanosoma cruzi (Tulahuen 2 strain) and were non-toxic at the highest assayed doses rendering selectivity indexes (IC(50) (macrophages)/IC(50) (Trypanosoma cruzi)) of >25 for 7a and >20 for 8a, with IC(50) values in macrophages >400 microM.

Mode of action of Nifurtimox and N-oxide-containing heterocycles against Trypanosoma cruzi: Is oxidative stress involved?

Chagas disease is caused by the trypanosomatid parasite Trypanosoma cruzi and threatens millions of lives in South America. As other neglected diseases there is almost no research and development effort by the pharmaceutical industry and the treatment relies on two drugs, Nifurtimox and Benznidazole, discovered empirically more than three decades ago. Nifurtimox, a nitrofurane derivative, is believed to exert its biological activity through the bioreduction of the nitro-group to a nitro-anion radical which undergoes redox-cycling with molecular oxygen. This hypothesis is generally accepted, although arguments against it have been presented. In the present work we studied the ability of Nifurtimox and five N-oxide-containing heterocycles to induce oxidative stress in T. cruzi. N-Oxide-containing heterocycles represent a promising group of new trypanosomicidal agents and their mode of action is not completely elucidated. The results here obtained argue against the oxidative stress hypothesis almost for all the studied compounds, including Nifurtimox. A significant reduction in the level of parasitic low-molecular-weight thiols was observed after Nifurtimox treatment; however, it was not linked to the production of reactive oxidant species. Besides, redox-cycling is only observed at high Nifurtimox concentrations (>400microM), two orders of magnitude higher than the concentration required for anti-proliferative activity (5microM). Our results indicate that an increase in oxidative stress is not the main mechanism of action of Nifurtimox. Among the studied N-oxide-containing heterocycles, benzofuroxan derivatives strongly inhibited parasite dehydrogenase activity and affected mitochondrial membrane potential. The indazole derivative raised intracellular oxidants production, but it was the least effective as anti-T. cruzi.

Platinum-based complexes of bioactive 3-(5-nitrofuryl)acroleine thiosemicarbazones showing anti-Trypanosoma cruzi activity.

Eight new platinum(II) complexes with 3-(5-nitrofuryl)acroleine thiosemicarbazones showing anti-trypanosomal activity were synthesized, characterized and in vitro evaluated. Most of the complexes showed IC(50) values in the micromolar range against two different strains of Trypanosoma cruzi, causative agent of Chagas disease (American Trypanosomiasis). In addition, most of the newly developed complexes, together with the analogous platinum 5-nitrofuraldehyde containing thiosemicarbazones previously reported, resulted more active than the reference trypanocidal drug nifurtimox on the infective trypomastigote form of the parasite. Their capacity to produce free radicals that could lead to parasite death was evaluated by ESR experiments in the parasite and by respiration measurements. Compounds were tested for their DNA interaction ability. Results showed that some of the compounds could act as dual inhibitors in the parasite, through production of toxic free radicals and interaction with DNA. All the results were compared with those previously reported for the free ligands, the analogous palladium(II) compounds and the previously reported series of platinum(II) compounds.

Synthesis and anti-trypanosomal activity of novel 5-nitro-2-furaldehyde and 5-nitrothiophene-2-carboxaldehyde semicarbazone derivatives

Several novel semicarbazones derivatives were prepared from 5-nitro-2-furaldehyde or 5-nitrothiophene-2-carboxaldehyde, and tested in vitro as potential anti-trypanosomal agents. The compounds were prepared in good to excellent yields in 2-3 steps from readily available starting materials. Some derivatives were found to be active against Trypanosoma cruzi with an activity similar to that of Nifurtimox.

Risedronate metal complexes potentially active against Chagas disease.

In the search for new metal-based drugs for the treatment of Chagas disease, the most widespread Latin American parasitic disease, novel complexes of the bioactive ligand risedronate (Ris, (1-hydroxy-1-phosphono-2-pyridin-3-yl-ethyl)phosphonate), [M(II)(Ris)(2)]·4H(2)O, where M═Cu, Co, Mn and Ni, and [Ni(II)(Ris)(2)(H(2)O)(2)]·H(2)O were synthesized and characterized by using analytical measurements, thermogravimetric analyses, cyclic voltammetry and infrared and Raman spectroscopies. Crystal structures of [Cu(II)(Ris)(2)]·4H(2)O and [Ni(II)(Ris)(2)(H(2)O)(2)]·H(2)O were solved by single crystal X-ray diffraction methods. The complexes, as well as the free ligand, were evaluated in vitro against epimastigotes and intracellular amastigotes of the parasite Trypanosoma cruzi, causative agent of Chagas disease. Results demonstrated that the coordination of risedronate to different metal ions improved the antiproliferative effect against T. cruzi, exhibiting growth inhibition values against the intracellular amastigotes ranging the low micromolar levels. In addition, this strong activity could be related to high inhibition of farnesyl diphosphate synthase enzyme. On the other hand, protein interaction studies showed that all the complexes strongly interact with albumin thus providing a suitable means of transporting them to tissues in vivo.

1,2,5-Oxadiazole N-oxide derivatives as potential anti-cancer agents: synthesis and biological evaluation. Part IV

Several new 1,2,5-oxadiazole N-oxide derivatives and some deoxygenated analogues were synthesized to be tested as potential selective hypoxic cell cytotoxins. Compounds prepared were designed in order to gain insight into the mechanism of action of this kind of cytotoxin. Compounds were tested in oxia and hypoxia and they proved to be non-selective. 3-Cyano-N(2)-oxide-4-phenyl-1,2,5-oxadiazole showed the best cytotoxic activity in oxia. The cytotoxicity observed for these derivatives could be explained in terms of the electronic characteristics of the 1,2,5-oxadiazole substituents. Electrochemical and ESR studies were performed on the more cytotoxic derivative.

Synthetic Medicinal Chemistry in Chagas’ Disease: Compounds at The Final Stage of “Hit-To-Lead” Phase

Chagas’ disease, or American trypanosomosiasis, has been the most relevant illness produced by protozoa in Latin America. Synthetic medicinal chemistry efforts have provided an extensive number of chemodiverse hits at the “active-to-hit” stage. However, only a more limited number of these have been studied in vivo in models of Chagas’ disease. Herein, we survey some of the cantidates able to surpass the “hit-to-lead” stage discussing their limitations or merit to enter in clinical trials in the short term.