Discovery of 1,3,4,5-tetrasubstituted pyrazoles as anti-trypanosomatid agents: Identification of alterations in flagellar structure of L. amazonensis

Drug Discovery for Cutaneous Leishmaniasis: A Review of Developments in the Past 15 Years

Leishmaniasis is a group of vector-borne, parasitic diseases caused by over 20 species of the protozoan Leishmania spp. The three major disease classifications, cutaneous, visceral, and mucocutaneous, have a range of clinical manifestations from self-healing skin lesions to hepatosplenomegaly and mucosal membrane damage to fatality. As a neglected tropical disease, leishmaniasis represents a major international health challenge, with nearly 350 million people living at risk of infection a year. The current chemotherapeutics used to treat leishmaniasis have harsh side effects, prolonged and costly treatment regimens, as well as emerging drug resistance, and are predominantly used for the treatment of visceral leishmaniasis. There is an undeniable need for the identification and development of novel chemotherapeutics targeting cutaneous leishmaniasis (CL), largely ignored by concerted drug development efforts. CL is mostly non-lethal and the most common presentation of this disease, with nearly 1 million new cases reported annually. Recognizing this unaddressed need, substantial yet fragmented progress in early drug discovery efforts for CL has occurred in the past 15 years and was outlined in this review. However, further work needs to be carried out to advance early discovery candidates towards the clinic. Importantly, there is a paucity of investment in the translation and development of therapies for CL, limiting the emergence of viable solutions to deal with this serious and complex international health problem.

A Review of the Recent Development in the Synthesis and Biological Evaluations of Pyrazole Derivatives

Pyrazoles are five-membered heterocyclic compounds that contain nitrogen. They are an important class of compounds for drug development; thus, they have attracted much attention. In the meantime, pyrazole derivatives have been synthesized as target structures and have demonstrated numerous biological activities such as antituberculosis, antimicrobial, antifungal, and anti-inflammatory. This review summarizes the results of published research on pyrazole derivatives synthesis and biological activities. The published research works on pyrazole derivatives synthesis and biological activities between January 2018 and December 2021 were retrieved from the Scopus database and reviewed accordingly.

Bioactivity of Novel Pyrazole-Thiazolines Scaffolds against Trypanosoma cruzi: Computational Approaches and 3D Spheroid Model on Drug Discovery for Chagas Disease

Chagas disease, a century-old disease that mainly affects the impoverished population in Latin America, causes high morbidity and mortality in endemic countries. The available drugs, benznidazole (Bz) and nifurtimox, have limited effectiveness and intense side effects. Drug repurposing, and the development of new chemical entities with potent activity against Trypanosoma cruzi, are a potential source of therapeutic options. The present study describes the biological activity of two new series of pyrazole-thiazoline derivatives, based on optimization of a hit system 5-aminopyrazole-imidazoline previously identified, using structure−activity relationship exploration, and computational and phenotype-based strategies. Promising candidates, 2c, 2e, and 2i derivatives, showed good oral bioavailability and ADMET properties, and low cytotoxicity (CC50 > 100 µM) besides potent activity against trypomastigotes (0.4−2.1 µM) compared to Bz (19.6 ± 2.3 µM). Among them, 2c also stands out, with greater potency against intracellular amastigotes (pIC50 = 5.85). The selected pyrazole-thiazoline derivatives showed good permeability and effectiveness in the 3D spheroids system, but did not sustain parasite clearance in a washout assay. The compounds’ mechanism of action is still unknown, since the treatment neither increased reactive oxygen species, nor reduced cysteine protease activity. This new scaffold will be targeted to optimize in order to enhance its biological activity to identify new drug candidates for Chagas disease therapy.

Microwave Assisted Biology-Oriented Drug Synthesis (BIODS) of NewN, N′-Disubstituted Benzylamine Analogous of 4-Aminoantipyrine against Leishmaniasis -In VitroAssay and In silico-Predicted Molecular Interactions with Key Metabolic Targets

Biology-Oriented Drug Synthesis (BIODS) deals with the simple chemical transformations on the commercially available drugs in order to enhance their new and diversified pharmacological profile. It opens new avenues for the rapid development of drug candidates for neglected tropical diseases (NTDs). Leishmaniasis is one of the NTDs which spread by the bite of sandflies (plebotomine). It ranges from cutaneous self-healing leishmaniasis to life threatening visceral leishmaniasis, known as kala-azar. The current treatment options include the use of pentamidine, miltefosine, and amphotericin B drugs. Unfortunately, all currently available drugs are associated with adverse effects, such as severe nephron- and cardiotoxicity, pancreatitis, and hepatotoxicity. This warrants the development of new drugs against leishmaniasis. Moreover, emergence of resistance against the current medications further worsens the conditions. With this objective, new N, N'-disubstituted benzylamine derivatives of ampyrone (4-aminoantipyrine) were synthesized by using ultrasonication, and microwave assistance. All derivatives were found to be new, except 1, 4, and 11. All the compounds were evaluated for their anti-leishmanial activity, and cellular cytotoxicity. Among them, compounds 4, 5, 8, and 9 showed a significant anti-leishmanial activity in vitro, in comparison to standard drug, miltefosine (IC₅₀ = 25.78 ± 0.2 µM). These compounds were also docked against various metabolic enzymes to predict their interactions and mechanism of action, and were found to act via targeting important enzymes of various metabolic pathways.

Synthesis, Structural Characterization, and In Vitro and In Silico Antifungal Evaluation of Azo-Azomethine Pyrazoles (PhN2(PhOH)CHN(C3N2(CH3)3)PhR, R = H or NO2)

The azo-azomethine imines, R¹-N=N-R²-CH=N-R³, are a class of active pharmacological ligands that have been prominent antifungal, antibacterial, and antitumor agents. In this study, four new azo-azomethines, R¹ = Ph, R² = phenol, and R³ = pyrazol-Ph-R’ (R = H or NO₂), have been synthesized, structurally characterized using X-ray, IR, NMR and UV–Vis techniques, and their antifungal activity evaluated against certified strains of Candida albicans and Cryptococcus neoformans. The antifungal tests revealed a high to moderate inhibitory activity towards both strains, which is regulated as a function of both the presence and the location of the nitro group in the aromatic ring of the series. These biological assays were further complemented with molecular docking studies against three different molecular targets from each fungus strain. Molecular dynamics simulations and binding free energy calculations were performed on the two best molecular docking results for each fungus strain. Better affinity for active sites for nitro compounds at the “meta” and “para” positions was found, making them promising building blocks for the development of new Schiff bases with high antifungal activity.