Synthesis, characterization, and NMR studies of 1,2,3-triazolium ionic liquids: a good perspective regarding cytotoxicity.

Ionic liquids (ILs) have been extensively studied and are considered green solvents capable of replacing traditional organic solvents. In this study, seven 1,2,3-triazolium derivative ILs have been synthesized. In order to study the effect of the cation nature on the ILs cytotoxicity, their structures were first identified by 1H, 13C NMR 1D, and 2D spectroscopy. DFT calculations have also been performed in a way to help to provide an insightful structural analysis from 13C NMR spectroscopy. The comparison made with the NMR experimental shifts was quite important to show that the 1,2,3-triazolium derivatives have the expected structure shown here. The in vitro cytotoxicity of ILs toward macrophages showed that among the compounds tested, five did not exhibit expressive cytotoxicity on mammalian cells. Besides the well-established relationship between the carbonic chain size of the cation and the cytotoxicity, the log P of the compounds predicts that the toxicity increases with the size of the carbon chain, demonstrating that the most cytotoxic compound is also the most lipophilic one. The low cytotoxicity effect of ILs on mammalian cells points to their potential application in large-scale by industry. Graphical abstract Seven triazolium ILs were synthesized and their in vitro cytotoxicity on murine macrophages showed a relationship with the carbonic chain size.

Effect of 1,2,3-triazole salts, non-classical bioisosteres of miltefosine, on Leishmania amazonensis.

Here, we report the effect of new non-classical bioisosteres of miltefosine on Leishmania amazonensis. Fifteen compounds were synthesized and the compound dhmtAc, containing an acetate anion, a side chain of 10 carbon atoms linked to N-1 and a methyl group linked to N-3, showed high and selective biological activity against L. amazonensis. On the intracellular amastigotes, stages of the parasite related to human disease, the IC50 values were near or similar to the 1.0µM (0.9, 0.8 and 1.0µM on L. amazonensis-WT, and two transgenic L. amazonensis expressing GFP and RFP, respectively), being more active than miltefosine. Furthermore, dhmtAc did not show toxic effects on human erythrocytes and macrophages (CC50=115.9µM) being more destructive to the intracellular parasites (selectivity index>115). Promastigotes and intramacrophage amastigotes treated with dhmtAc showed low capacity for reversion of the effect of the compound. A study of the mechanism of action of this compound showed some features of metazoan apoptosis, including cell volume decreases, loss of mitochondrial membrane potential, ROS production, an increase in the intracellular lipid bodies, in situ labeling of DNA fragments by TUNEL labeling and phosphatidylserine exposure to the outerleaflet of the plasma membrane. In addition, the plasma membrane disruption, revealed by PI labeling, suggests cell death by necrosis. No increase in autophagic vacuoles formation in treated promastigotes was observed. Taken together, the data indicate that the bioisostere of miltefosine, dhmtAc, has promising antileishmanial activity that is mediated via apoptosis and necrosis.

Antiplasmodial activity of chloroquine analogs against chloroquine-resistant parasites, docking studies and mechanisms of drug action.

BACKGROUND: Given the threat of resistance of human malaria parasites, including to artemisinin derivatives, new agents are needed. Chloroquine (CQ) has been the most widely used anti-malarial, and new analogs (CQAns) presenting alkynes and side chain variations with high antiplasmodial activity were evaluated. METHODS: Six diaminealkyne and diaminedialkyne CQAns were evaluated against CQ-resistant (CQ-R) (W2) and CQ-sensitive (CQ-S) (3D7) Plasmodium falciparum parasites in culture. Drug cytotoxicity to a human hepatoma cell line (HepG2) evaluated, allowed to calculate the drug selectivity index (SI), a ratio of drug toxicity to activity in vitro. The CQAns were re-evaluated against CQ-resistant and -sensitive P. berghei parasites in mice using the suppressive test. Docking studies with the CQAns and the human (HssLDH) or plasmodial lactate dehydrogenase (PfLDH) enzymes, and, a ß-haematin formation assay were performed using a lipid as a catalyst to promote crystallization in vitro. RESULTS: All tested CQAns were highly active against CQ-R P. falciparum parasites, exhibiting half-maximal inhibitory concentration (IC(50)) values below 1 µΜ. CQAn33 and CQAn37 had the highest SIs. Docking studies revealed the best conformation of CQAn33 inside the binding pocket of PfLDH; specificity between the residues involved in H-bonds of the PfLDH with CQAn37. CQAn33 and CQAn37 were also shown to be weak inhibitors of PfLDH. CQAn33 and CQAn37 inhibited ß-haematin formation with either a similar or a 2-fold higher IC(50) value, respectively, compared with CQ. CQAn37 was active in mice with P. berghei, reducing parasitaemia by 100%. CQAn33, -39 and -45 also inhibited CQ-resistant P. berghei parasites in mice, whereas high doses of CQ were inactive. CONCLUSIONS: The presence of an alkyne group and the size of the side chain affected anti-P. falciparum activity in vitro. Docking studies suggested a mechanism of action other than PfLDH inhibition. The ß-haematin assay suggested the presence of an additional mechanism of action of CQAn33 and CQAn37. Tests with CQAn34, CQAn37, CQAn39 and CQAn45 confirmed previous results against P. berghei malaria in mice, and CQAn33, 39 and 45 were active against CQ-resistant parasites, but CQAn28 and CQAn34 were not. The result likely reflects structure-activity relationships related to the resistant phenotype.

4-aminoquinoline analogues and its platinum (II) complexes as antimalarial agents.

The high incidence of malaria and drug-resistant strains of Plasmodium have turned this disease into a problem of major health importance. One of the approaches used to control it is to search for new antimalarial agents, such as quinoline derivates. This class of compounds composes a broad group of antimalarial agents, which are largely employed, and inhibits the formation of ß-haematin (malaria pigment), which is lethal to the parasite. More specifically, 4-aminoquinoline derivates represent potential sources of antimalarials, as the example of chloroquine, the most used antimalarial worldwide. In order to assess antimalarial activity, 12 4-aminoquinoline derived drugs were obtained and some of these derivatives were used to obtain platinum complexes platinum (II). These compounds were tested in vivo in a murine model and revealed remarkable inhibition of parasite multiplication values, whose majority ranged from 50 to 80%. In addition they were not cytotoxic. Thus, they may be object of further research for new antimalarial agents.

Synthesis of 4-aminoquinoline analogues and their platinum(II) complexes as new antileishmanial and antitubercular agents.

A series of 4-amino-7-chloroquinoline derivatives were synthesized by the reaction of 4,7-dichloro-quinoline with the corresponding diamine and then with propargyl bromide. In addition, platinum(II) complexes were obtained by reacting some of the organic derivatives with K(2)PtCl(4). Several of the synthesized compounds displayed antituberculosis activities. Compound 3 was 47.5 times more active than amphotericin B against Leishmania chagasi (IC(50)=0.04 µg/mL). Compounds 5, 6, 7, 9, 10, 11 and 13 presented promising results against Mycobacterium tuberculosis, with MIC values ranging from 12.5 to 15.6 µg/mL, comparable to the "first and second line" drugs used to treat tuberculosis.

Modulatory effects of 6-carboxymethylthiopurine on activated murine macrophages.

The immunological activity of macrophages against pathogens in hosts includes the phagocytosis and the production of nitric oxide. We report herein the investigation of the effect of 6-carboxymethylthiopurine on nitric oxide production by murine macrophages as well as its effect on the cell viability and proliferation after stimulus with Mycobacterium bovis bacille Calmette-Guérin, interferon-gamma or a combination of both. J774A.1 macrophages stimulated or not by bacille Calmette-Guérin (20 microg/mL), interferon-gamma or both, were cultured in the presence of 6-carboxymethylthiopurine (125, 250 and 500 microm). Nitric oxide production was measured by the Griess method and cell viability/proliferation by the diphenyltetrazolium assay [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide]. We observed an increase of J774A.1 cell proliferation after stimulus with bacille Calmette-Guérin at 125, 250 and 500 microm (69.1, 124.0 and 89.7%, respectively) and with interferon-gamma at 125 and 250 microm (64.8% and 61.7%, respectively) (p < 0.05). In all cultures treated with 6-carboxymethylthiopurine, interferon-gamma-activated nitric oxide production by J774A.1 cells decreased as well as when subjected to interferon-gamma plus bacille Calmette-Guérin stimuli at 500 microm (p < 0.05). Altogether these data point to an anti-inflammatory effect of 6-carboxymethylthiopurine on stimulated macrophages.