In vitro evaluation of 4-phenyl-5-(4′-X-phenyl)-1,3,4-thiadiazolium-2-phenylaminide chlorides and 3[N-4′-X-phenyl]-1,2,3-oxadiazolium-5-olate derivatives on nitric oxide synthase and arginase activities of Leishmania amazonensis

Novel trifluoromethyl sydnone derivatives: Design, synthesis and fungicidal activity

Crop pathogens reduce the yield and quality of agricultural production. The development of new fungicides will help to sustain this protection and overcome fungicide resistance. Sydnone is a kind of mesoionic, which has a wide range of biological activities. The application of sydnones in agriculture is less, and the study of these compounds will lead to the discovery of new active compounds. In this study, we designed and synthesized a series of noval sydnone mesoionic derivatives by active substructure splicing. All compounds were characterized using ¹H and ¹³C NMR spectroscopy. Among them, trifluoromethyl compound D17 showed good bioactivity against Pseudoperonospora cubensis (EC₅₀ = 49 mg L^-1) in vivo, the activity was similar to that of the control Kresoxim-methyl (EC₅₀ = 44 mg L^-1). However, the target of these compounds should not only be tyrosinase, and the mode of action needs to be further studied. In addition, the structure-activity relationship indicated that the trifluoromethyl group was more beneficial for antifungal activity. This is the first report that fluorine-containing N(3)-benzyl sydnone compounds have good fungicidal activity. These results will provide a basis for the development of sydnone mesoionic as new lead fungicidal agents.

Leishmanicidal effect of 1,3,4-thiadiazolium mesoionic salts on Leishmania amazonensis in vitro

Leishmaniasis is a neglected broad clinical spectrum disease caused by protozoa of the genus Leishmania, which affect millions of people annually in the world and the treatment has severe side effects and resistant strains have been reported. Mesoionic salts are a subclass of the betaine group with extensive biological activity such as microbicide and anti-inflammatory In this work, we analyze the cytotoxic effects of mesoionic salts, 4-phenyl-5-(X-phenyl)-1,3,4-thiadiazolium-2-phenylamine chloride (X = 4 Cl; 3,4 diCl and 3,4 diF), on Leishmania amazonensis in vitro. Initially, Mesoionic salts toxicity were evaluated by XTT assay on L. amazonensis promastigotes. Our results show that the mesoionic salts MI-3,4 diCl, MI-4 Cl and MI-3,4 diF were toxic to the promastigote parasite with IC₅₀ values of 14.3, 40.1 and 61.8 μM, respectively. The amastigote survival was evaluated in treated infected-macrophages, and the results demonstrate that MI-4 Cl (IC₅₀ = 33 μM) and MI-3,4 diCl (IC₅₀ = 43 μM) have a toxic effect against these forms. None of the mesoionic compounds tested present host cell toxicity up to the tested concentration of 100 μM. The selectivity index for MI-3,4 diCl and MI-4 Cl were 3.94 and 6.97, respectively. Nitric oxide (NO) production assayed by Griess reagent, in LPS-activated macrophages or not, in the presence of the salts showed that only the MI-3,4 diCl compound reduced NO levels. Lipid profile analysis of treated-promastigotes showed no alteration of neutral lipids. Evaluation of mitochondrial membrane potential (∆Ψm) showed that the MI-4Cl compound was able to reduce (∆Ψm) by 50%. Therefore, our results suggest that the chlorinated compounds are promising biomolecules, which cause inhibition of L.amazonensis promastigotes, amastigotes, leading to mitochondrial damage.

Synthetic (E)-3-Phenyl-5-(phenylamino)-2-styryl-1,3,4-thiadiazol-3-ium Chloride Derivatives as Promising Chemotherapy Agents on Cell Lines Infected with HTLV-1

Synthesis of four compounds belonging to mesoionic class, (E)-3-phenyl-5-(phenylamino)-2-styryl-1,3,4-thiadiazol-3-ium chloride derivatives (5a–d) and their biological evaluation against MT2 and C92 cell lines infected with human T-cell lymphotropic virus type-1 (HTLV-1), which causes adult T-cell leukemia/lymphoma (ATLL), and non-infected cell lines (Jurkat) are reported. The compounds were obtained by convergent synthesis under microwave irradiation and the cytotoxicity was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Results showed IC₅₀ values of all compounds in the range of 1.51–7.70 μM in HTLV-1-infected and non-infected cells. Furthermore, it was observed that 5b could induce necrosis after 24 h for Jurkat and MT2 cell lines. The experimental (fluorimetric method) and theoretical (molecular docking) results suggested that the mechanism of action for 5b could be related to its capacity to intercalate into DNA. Moreover, the preliminary pharmacokinetic profile of the studied compounds (5a–d) was obtained through human serum albumin (HSA) binding affinity using multiple spectroscopic techniques (circular dichroism, steady-state and time-resolved fluorescence), zeta potential and molecular docking calculations. The interaction HSA:5a–d is spontaneous and moderate (K_a ~ 10⁴ M⁻¹) via a ground-state association, without significantly perturbing both the secondary and surface structures of the albumin in the subdomain IIA (site I), indicating feasible biodistribution in the human bloodstream.

Leishmania Spp-Host Interaction: There Is Always an Onset, but Is There an End?

For a long time Leishmaniasis had been considered as a neglected tropical disease. Recently, it has become a priority in public health all over the world for different aspects such as geographic spread, number of population living at risk of infection as well as the potential lethality and/or the development of disfiguring lesions in the, respectively, visceral and tegumentary forms of the disease. As a result, several groups have been bending over this issue and many valuable data have been published. Nevertheless, parasite-host interactions are still not fully known and, consequently, we do not entirely understand the infection dynamics and parasite persistence. This knowledge may point targets for modulation or blockage, being very useful in the development of measures to interfere in the course of infection/ disease and to minimize the risks and morbidity. In the present review we will discuss some aspects of the Leishmania spp-mammalian host interaction in the onset of infection and after the clinical cure of the lesions. We will also examine the information already available concerning the parasite strategy to evade immune response mainly at the beginning of the infection, as well as during the parasite persistence. This knowledge can improve the conditions of treatment, follow-up and cure control of patients, minimizing the potential damages this protozoosis can cause to infected individuals.

Future Prospects in the Treatment of Parasitic Diseases: 2-Amino-1,3,4-Thiadiazoles in Leishmaniasis

Neglected tropical diseases affect the lives of a billion people worldwide. Among them, the parasitic infections caused by protozoan parasites of the Trypanosomatidae family have a huge impact on human health. Leishmaniasis, caused by Leishmania spp., is an endemic parasitic disease in over 88 countries and is closely associated with poverty. Although significant advances have been made in the treatment of leishmaniasis over the last decade, currently available chemotherapy is far from satisfactory. The lack of an approved vaccine, effective medication and significant drug resistance worldwide had led to considerable interest in discovering new, inexpensive, efficient and safe antileishmanial agents. 1,3,4-Thiadiazole rings are found in biologically active natural products and medicinally important synthetic compounds. The thiadiazole ring exhibits several specific properties: it is a bioisostere of pyrimidine or benzene rings with prevalence in biologically active compounds; the sulfur atom increases lipophilicity and combined with the mesoionic character of thiadiazoles imparts good oral absorption and good cell permeability, resulting in good bioavailability. This review presents synthetic 2-amino-1,3,4-thiadiazole derivatives with antileishmanial activity. Many reported derivatives can be considered as lead compounds for the synthesis of future agents as an alternative to the treatment of leishmaniasis.

Novel piperonal 1,3,4-thiadiazolium-2-phenylamines mesoionic derivatives: Synthesis, tyrosinase inhibition evaluation and HSA binding study

A novel series of piperonal mesoionic derivatives (PMI 1-6) was synthesized. Tyrosinase inhibition in the presence of PMI-1, -2, -3, -4, -5 and -6 as well as human serum albumin (HSA) binding studies with PMI-5 and PMI-6 were done by spectroscopic and theoretical methods. The mesoionic compound PMI-5 is the most promising tyrosinase inhibitor with a noncompetitive inhibitory mechanism and an IC₅₀=124μmolL^-1. In accordance with the kinetic profile, molecular docking results show that PMI-5 is able to interact favorably with the tyrosinase active site containing the substrate molecule, L-DOPA, interacting with Val-247, Phe-263 and Val-282 residues. The spectroscopic results for the interaction HSA:PMI-5 and HSA:PMI-6 indicated that these mesoionic compounds can associate with HSA in the ground state and energy transfer can occur with high probability. The binding was moderate, spontaneous and can perturb significantly the secondary structure of the albumin. The molecular docking results suggest that PMI-5 and PMI-6 are able to be accommodated inside the Sudlow's site I in HSA, interacting with hydrophobic and hydrophilic amino acid residues.