Maurício Silva dos Santos

Chagas disease urgently requires the development of new, safe, and effective therapies. We evaluated a series of 6‐hydroxy‐3‐aryl/heteroarylcoumarin derivatives against Trypanosoma cruzi to identify candidates with multistage activity. Our screening revealed that derivatives 1c (2‐pyridyl) and 1f (2,3‐dihydrobenzo[ b ][1,4]dioxine) are highly selective chemotypes toward trypomastigotes over Vero cells (SI = 549.45 and > 625, respectively), demonstrating submicromolar potency (IC ₅₀ = 0.91 and 0.80 μM, respectively), an activity up to 23‐fold higher than benznidazole (Bz). The derivative 1f , like Bz, also exhibited dual‐stage activity, showing intracellular amastigote activity (IC ₅₀ ∼ 10 μM). Mechanistic analysis using a washout assay revealed that, rather than eliminating intracellular forms, 1f prevents the release of new trypomastigotes. Our findings suggest that 1f targets the amastigote‐to‐trypomastigote differentiation pathway. The retention of a high intracellular parasitic load and the absence of trypomastigote release during the washout period strongly suggest that 1f acts as a selective inhibitor of metacyclogenesis. This insight positions the coumarin scaffold bearing a 2,3‐dihydrobenzo[ b ][1,4]dioxine substituent at position 3 as a promising starting point for developing improved multi‐stage therapeutic candidates against Trypanosoma cruzi .

Pyrazole-thiazole hybrids 1-(a-k) were synthesized and fully characterized to investigate their biological activities against Trypanosoma cruzi and Mycobacterium tuberculosis . Physicochemical profiling confirmed favorable drug-like properties across the series. Biological assays identified compound 1g (3-F) as the most active against T. cruzi, with IC₅₀ values of 11.66 μM (SI > 42.8) in trypomastigotes and 26.83 μM (SI > 18.9) in amastigotes. Compound 1h (4-Br) displayed significant antimycobacterial activity, with a MIC of 32.28 μM against the H37Rv strain. In silico analyses suggested preferential stabilization of halogenated derivatives through hydrophobic and π-driven interactions in structurally related enzymatic pockets, used here as an exploratory model. Taken together, these findings demonstrate that halogen substitution strongly modulates affinity and biological performance, supporting pyrazole-thiazole hybrids as promising scaffolds for further optimization against neglected-parasite pathogens. Future studies expanding halogen patterns and probing alternative binding pockets may improve potency and target selectivity across this chemical space.

Background: Chagas disease poses a significant public health challenge, particularly impacting socioeconomically vulnerable populations. Current treatment strategies still rely on two nitro heterocyclic compounds: benznidazole and nifurtimox. Both agents exhibit limited therapeutic efficacy during the chronic phase of the disease and are often linked to severe adverse effects that frequently lead to treatment discontinuation. This urgent need for safer, more effective oral treatments drives the development of novel chemotypes. Objective: In this study, we advanced the preclinical evaluation of 4-imidazoline-1H-pyrazole derivatives, which have been identified as promising candidates against Trypanosoma cruzi. Methods: The candidate compound identified from the reversibility assay underwent further evaluation for its efficacy using a three-dimensional (3D) culture model and a Transwell co-culture system, in addition to the in vivo assessment. Results: Our findings revealed that compound 3m (3-Cl, 4-CH₃) exhibited low cytotoxicity while substantially decreasing the parasite burden in 3Dcardiac spheroid models. The compound effectively permeated Caco-2 cell monolayers and demonstrated the ability to inhibit T. cruzi infection in Vero cell cultures within a co-culture system. Furthermore, the 3m derivative not only controlled parasite resurgence but also showed significant therapeutic benefits in a murine model of acute T. cruzi infection, resulting in marked reductions in parasitemia and tissue parasitism, associated with diminished inflammatory infiltrate and cardiac fibrosis. Treatment with 3m increased the survival rate of infected mice to 40%, comparable to the reference drug benznidazole in several key pathological endpoints. Conclusion: These findings highlight the potential of 4-imidazoline-1H-pyrazole derivatives, particularly compound 3m, in mitigating the pathological effects associated with T. cruzi infection.

Background: Chagas disease (CD), a life-threatening disease caused by Trypanosoma cruzi, remains a significant global public health concern. The limited efficacy of the available drugs (nifurtimox and benznidazole), their severe adverse events, and the unsatisfactory outcomes of clinical trials drive the search for new, effective, and safe drugs. Objective: This study describes the synthesis, structural characterization, and in vitro antiparasitic activity of novel pyrazole-benzimidazole derivatives against mammalian developmental stages of T. cruzi. Methods: Phenotypic screening was used to assess the effect of pyrazole-benzimidazole derivatives against T. cruzi. Three-dimensional cardiac spheroids were employed to evaluate the toxic effect and drug efficacy. Molecular docking and cysteine protease activity were also performed. Results: Pyrazole-benzimidazole derivatives showed activity against both trypomastigotes and intracellular amastigotes. Compounds 1i (IC50 = 6.6 μM) and 1j (IC50 = 9.4 μM) demonstrated the most potent activity with a high selectivity index (SI > 45) against intracellular amastigotes. Both compounds exhibited high efficacy on 3D cardiac spheroids, effectively reducing the parasite load by over 80%. Molecular docking analysis revealed that both compounds target the catalytic domain of cruzain through pi-stacking and hydrogen bonding interactions and inhibit T. cruzi cysteine protease. These derivatives also showed an additive effect in combination with the reference drug (Bz). Conclusion: Our findings emphasize the significance of pyrazole-benzimidazole hybrids in the search for new anti-T. cruzi agents.

Chagas disease, caused by Trypanosoma cruzi, poses a significant public health challenge due to its widespread prevalence, limited therapeutic options, and adverse effects associated with available medications. In this study, we developed 13 novel pyrazole-imidazoline derivatives, inspired by a previously identified cysteine protease inhibitor, and evaluated their antiparasitic activity. Our in silico analyses predicted favorable physicochemical profiles and promising oral bioavailability for these derivatives. Upon phenotypic screening, we observed that these new derivatives exhibited low cytotoxicity (CC₅₀ > 100 µM) and marked efficacy against intracellular amastigotes. Derivative 1k showed high activity (IC₅₀ = 3.3 ± 0.2 µM), selectivity (SI = 73.9), and potency (pIC₅₀ = 5.4). In a 3D cardiac microtissue model, 1k significantly reduced parasite load, matching the efficacy of benznidazole (Bz) even at lower concentrations. Both 1k and Bz effectively prevented parasite recrudescence; however, neither resulted in parasite sterility under the experimental conditions employed. The combination of 1k–Bz yielded an additive interaction, highlighting its potential for in vivo combination therapy. While structural changes abolished cysteine protease inhibition, incorporating a CF₃ substituent at the para position and excluding the amino group enhanced antiparasitic activity. These findings reinforce the promise of the pyrazole-imidazoline scaffold and support further structural optimizations to develop innovative candidates for treating Chagas disease.

Oxazolines are important heterocyclic systems due to their biological activities, such as antibacterial, antimalarial, anticancer, antiviral, anti-inflammatory, antifungal, antipyretic, and antileishmanial. They have been widely applied as chiral auxiliaries, polymers, catalysts, protecting groups, building blocks, and ligands in asymmetric synthesis. Due to their importance, many synthetic routes to prepare oxazoline moieties have been investigated and developed by researchers around the world. In this review, we summarized several synthetic methodologies published in the literature. The main substrates are nitriles, carboxylic acids, and acid derivatives, which react with a variety of reactants under conventional heating, microwave irradiation or ultrasound irradiation conditions. Syntheses via intramolecular cyclisation from amides have also been reported. Many publications have highlighted procedures based on solvent-free conditions using eco-friendly, reusable, and easy-availability catalysts.

Imidazole is one of the most important heterocyclic rings. This nucleus can be found in a plethora of substances in different knowledge areas such as medicinal, agrochemical, polymer, and dyestuff. N‐alkylation reactions involving N − 1 atom is a remarkable tool to synthesize many imidazole derivatives which can be attached to a great variety of functional groups. In this work, we synthesized 10 new intermediates 4‐chlorobutyl 1‐aryl‐1H‐pyrazole‐4‐carboxylates 3(a–j) from 1‐aryl‐1H‐pyrazole‐4‐carbonyl chlorides, obtained from 1‐aryl‐1H‐pyrazole‐4‐carboxylic acids 4(a–j), and 4‐chlorobutan‐1‐ol 1, generated by THF ring‐opening promoted by hydrochloric acid. Compounds 3(a–j) promoted N‐alkylation of 4(5)‐nitro‐1H‐imidazole to afford the targets 4‐(4‐nitro‐1H‐imidazol‐1‐yl)butyl 1‐aryl‐1H‐pyrazole‐4‐carboxylates 2(a–j) in 18%–85% yields.

Chagas disease, a silent but widespread disease that mainly affects a socioeconomically vulnerable population, lacks innovative safe drug therapy. The available drugs, benznidazole and nifurtimox, are more than fifty years old, have limited efficacy, and carry harmful side effects, highlighting the need for new therapeutics. This study presents two new series of pyrazole-thiadiazole compounds evaluated for trypanocidal activity using cellular models predictive of efficacy. Derivatives 1c (2,4-diCl) and 2k (4-NO₂) were the most active against intracellular amastigotes. Derivative 1c also showed activity against trypomastigotes, with the detachment of the flagellum from the parasite body being a predominant effect at the ultrastructural level. Analogs have favorable physicochemical parameters and are predicted to be orally available. Drug efficacy was also evaluated in 3D cardiac microtissue, an important target tissue of Trypanosoma cruzi, with derivative 2k showing potent antiparasitic activity and a significant reduction in parasite load. Although 2k potentially reduced parasite load in the washout assay, it did not prevent parasite recrudescence. Drug combination analysis revealed an additive profile, which may lead to favorable clinical outcomes. Our data demonstrate the antiparasitic activity of pyrazole-thiadiazole derivatives and support the development of these compounds using new optimization strategies.

Background: A series of new eight 2-(1-aryl-3-methyl-1H-pyrazol-4-yl)-1,4,5,6-tetrahydropyrimidines 1(a-h) were synthesized by microwave irradiation technique. In vitro phenotypic screening was performed to evaluate the effect of these compounds on intracellular amastigotes forms of Trypanosoma cruzi, the etiological agent of Chagas disease. Methods: Compounds 1(a-h) were synthesized from pyrazole-carbonitriles 2(a-h) employing microwave irradiation (50W) for 10-20 minutes. Physicochemical properties were calculated using OSIRIS DataWarrior. The toxic effect on mammalian cells (Vero Cells) and the trypanocidal activity against Trypanosoma cruzi (Dm28c-Luc) were also evaluated. Results: Compounds 1(a-h) were obtained in 24-94% yields. They were completely characterized by Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and High-Resolution Mass Spectrometry (HRMS) analyses. The derivatives showed low trypanocidal activity, with IC50 ranging from 47.16 to > 100 μM, with lower activity than benznidazole (1.93 μM) used as reference drug. Conclusion: The attractive features of this synthetic methodology are mild conditions, short reaction time, and low power. All derivatives showed low toxicity in mammalian cells, good oral bioavailability, and did not violate Lipinski´s rule of 5.