1,3-Thiazole derivatives as privileged structures for anti-Trypanosoma cruzi activity: Rational design, synthesis, in silico and in vitro studies.

Chagas disease is a deadly and centenary neglected disease that is recently surging as a potential global threat. Approximately 30% of infected individuals develop chronic Chagas cardiomyopathy and current treatment with the reference benznidazole (BZN) is ineffective for this stage. We presently report the structural planning, synthesis, characterization, molecular docking prediction, cytotoxicity, in vitro bioactivity and mechanistic studies on the anti-T. cruzi activity of a series of 16 novel 1,3-thiazoles (2-17) derived from thiosemicarbazones (1a, 1b) in a two-step and reproducible Hantzsch-based synthesis approach. The anti-T. cruzi activity was evaluated in vitro against the epimastigote, amastigote and trypomastigote forms of the parasite. In the bioactivity assays, all thiazoles were more potent than BZN against epimastigotes. We found that the compounds presented an overall increased anti-tripomastigote selectivity (Cpd 8 was 24-fold more selective) than BZN, and they mostly presented anti-amastigote activity at very low doses (from 3.65 µM, cpd 15). Mechanistic studies on cell death suggested that the series of 1,3-thiazole compounds herein reported cause parasite cell death through apoptosis, but without compromising the mitochondrial membrane potential. In silico prediction of physicochemical properties and pharmacokinetic parameters showed promising drug-like results, being all the reported compounds in compliance with Lipinski and Veber rules. In summary, our work contributes towards a more rational design of potent and selective antitripanosomal drugs, using affordable methodology to yield industrially viable drug candidates.

Structural design, synthesis and anti-Trypanosoma cruzi profile of the second generation of 4-thiazolidinones chlorine derivatives.

Chagas disease causes more deaths in the Americas than any other parasitic disease. Initially confined to the American continent, it is increasingly becoming a global health problem. In fact, it is considered to be an "exotic" disease in Europe, being virtually undiagnosed. Benznidazole, the only drug approved for treatment, effectively treats acute-stage Chagas disease, but its effectiveness for treating indeterminate and chronic stages remains uncertain. Previously, our research group demonstrated that 4-thiazolidinones presented anti-T. cruzi activity including in the in vivo assays in mice, making this fragment appealing for drug development. The present work reports the synthesis and anti-T. cruzi activities of a novel series of 4-thiazolidinones derivatives that resulted in an increased anti-T. cruzi activity in comparison to thiosemicarbazones intermediates. Compounds 2c, 2e, and 3a showed potent inhibition of the trypomastigote form of the parasite at low cytotoxicity concentrations in mouse splenocytes. Besides, all the 2c, 2e, and 3a tested concentrations showed no cytotoxic activity on macrophages cell viability. When macrophages were submitted to T. cruzi infection and treated with 2c and 3a, compounds reduced the release of trypomastigote forms. Results also showed that the increased trypanocidal activity induced by 2c and 3a is independent of nitric oxide release. Flow cytometry assay showed that compound 2e was able to induce necrosis and apoptosis in trypomastigotes. Parasites treated with the compounds 2e, 3a, and 3c presented flagellum shortening, retraction and curvature of the parasite body, and extravasation of the internal content. Together, these data revealed a novel series of 4-thiazolidinones fragment-based compounds with potential effects against T. cruzi and lead-like characteristics.

Study of acute oral toxicity of the thiazole derivative N-(1-methyl-2-methyl-pyridine)-N-(p-bromophenylthiazol-2-yl)-hydrazine in a Syrian hamster.

The thiazole derivative N-1-methyl-2-methyl-pyridine)-N-(p-bromophenylthiazol-2-yl)-hydrazine was used to evaluate the acute oral toxicity in Syrian hamsters. The concentration of the doses (300 mg/kg and 2000 mg/kg) were based on the "Class Acute Toxicity Method" displayed in the OECD-423 guide. In addition, renal and liver biochemical tests were performed, as well as histopathological analysis. Our results showed that the compound's lethal dose (LD50) was 1000 mg/kg and classified as category 4 according to the criteria adopted in the experiment's protocol. Biochemical analysis of the liver function's parameters showed that the LD50 values in all animals were higher than the reference values. However, the analyze of the kidney injury parameters showed an increase in the urea's dosage but a decrease in the albumin's dosage in all animals when compared to the reference values. Kidney biochemical analysis also showed that creatinine's level was only higher than the reference values in one animal. Massive damages in the liver were observed, such as hypertrophy and hyperplasia of the hepatocyte, coagulation necrosis, the presence of mononuclear cells in the sinusoidal capillaries, steatosis, cholestasis, and congestion of sinusoidal capillaries and central-lobular veins. The animals presented renal injuries related to congestion of glomerular and interstitial capillaries, nephrosis of contorted proximal and distal tubules and congestion in the medullary region. In conclusion, the thiazole derivative was well tolerated although it caused acute liver and kidney damages. Therefore, these results showed the need of further investigation of this compound in vivo to evaluate the potential therapeutic effects with chronic models.

Dual Parasiticidal Activities of Phthalimides: Synthesis and Biological Profile against Trypanosoma cruzi and Plasmodium falciparum.

Chagas disease and malaria are two neglected tropical diseases (NTDs) that prevail in tropical and subtropical regions in 149 countries. Chagas is also present in Europe, the US and Australia due to immigration of asymptomatic infected individuals. In the absence of an effective vaccine, the control of both diseases relies on chemotherapy. However, the emergence of parasite drug resistance is rendering currently available drugs obsolete. Hence, it is crucial to develop new molecules. Phthalimides, thiosemicarbazones, and 1,3-thiazoles have been used as scaffolds to obtain antiplasmodial and anti-Trypanosoma cruzi agents. Herein we present the synthesis of 24 phthalimido-thiosemicarbazones (3 a-x) and 14 phthalimido-thiazoles (4 a-n) and the corresponding biological activity against T. cruzi, Plasmodium falciparum, and cytotoxicity against mammalian cell lines. Some of these compounds showed potent inhibition of T. cruzi at low cytotoxic concentrations in RAW 264.7 cells. The most active compounds, 3 t (IC50 =3.60 µM), 3 h (IC50 =3.75 µM), and 4 j (IC50 =4.48 µM), were more active than the control drug benznidazole (IC50 =14.6 µM). Overall, the phthalimido-thiosemicarbazone derivatives were more potent than phthalimido-thiazole derivatives against T. cruzi. Flow cytometry assay data showed that compound 4 j was able to induce necrosis and apoptosis in trypomastigotes. Analysis by scanning electron microscopy showed that T. cruzi trypomastigote cells treated with compounds 3 h, 3 t, and 4 j at IC50 concentrations promoted changes in the shape, flagella, and surface of the parasite body similar to those observed in benznidazole-treated cells. The compounds with the highest antimalarial activity were the phthalimido-thiazoles 4 l (IC50 =1.2 µM), 4 m (IC50 =1.7 µM), and 4 n (IC50 =2.4 µM). Together, these data revealed that phthalimido derivatives possess a dual antiparasitic profile with potential effects against T. cruzi and lead-like characteristics.