Functionalized 1,2,3-triazolium salts as potential agents against visceral leishmaniasis.

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, being fatal if untreated. In search of a more effective treatment for VL, one of the main strategies is the development and screening of new antileishmanial compounds. Here, we reported the synthesis of seven new acetyl functionalized 1,2,3-triazolium salts, together with four 1,2,3-triazole precursors, and investigated their effect against different strains of L. infantum from dogs and humans. The 1,2,3-triazolium salts exhibited better activity than the 1,2,3-triazole derivatives with IC50 range from 0.12 to 8.66 µM and, among them, compound 5 showed significant activity against promastigotes (IC50 from 4.55 to 5.28 µM) and intracellular amastigotes (IC50 from 5.36 to 7.92 µM), with the best selective index (SI ~ 6-9) and reduced toxicity. Our findings, using biochemical and ultrastructural approaches, demonstrated that compound 5 targets the mitochondrion of L. infantum promastigotes, leading to the formation of reactive oxygen species (ROS), increase of the mitochondrial membrane potential, and mitochondrial alteration. Moreover, quantitative transmission electron microscopy (TEM) revealed that compound 5 induces the reduction of promastigote size and cytoplasmic vacuolization. Interestingly, the effect of compound 5 was not associated with apoptosis or necrosis of the parasites but, instead, seems to be mediated through a pathway involving autophagy, with a clear detection of autophagic vacuoles in the cytoplasm by using both a fluorescent marker and TEM. As for the in vivo studies, compound 5 showed activity in a mouse model of VL at 20 mg/kg, reducing the parasite load in both spleen and liver (59.80% and 26.88%, respectively). Finally, this compound did not induce hepatoxicity or nephrotoxicity and was able to normalize the altered biochemical parameters in the infected mice. Thus, our findings support the use of 1,2,3-triazolium salts as potential agents against visceral leishmaniasis.

In silico, in vitro and in vivo studies indicate resveratrol analogue as a potential alternative for neuroinflammatory disorders.

Inflammaging is known as an imbalance between pro-inflammatory and anti-inflammatory immune mechanisms, being related to the onset of neurological disorders, such as major depression and Alzheimer's disease. Considering the known disadvantages regarding the FDA approved drug to manage such illnesses, resveratrol emerges as a natural drug candidate, despite its low bioavailability. In this study, resveratrol analogues were evaluated for their capacity of inhibiting acetylcholinesterase in silico, in vitro, and in vivo. Molecular docking simulations pointed out RSVA1 and RSVA6 as potent inhibitors, even more than resveratrol. Ellman's assay demonstrated RSVA6 as capable of inhibiting 92.4% of the enzyme activity. Further, male Swiss mice were pretreated with RSVA6 (100 mg kg-1) 60 min before receiving scopolamine (1 mg kg-1). The Novel Recognition Object (NOR), Object Location (OLT), and Buried Pellet tests (BPL) demonstrated an RSVA6 neuroprotective effect. In the second round of tests, mice received a single intraperitoneal injection of lipopolysaccharide (0.5 mg kg-1) 24 h before treatment with RSVA6 (1, 10, and 100 mg kg-1). The Open Field (OFT), Tail Suspension (TST), and Splash tests (ST) were evaluated. LPS had no significant effect on the crossing and rearing number, indicating an association between the immobility time and anhedonia observed in the TST and ST, respectively, with depressive-like behavior. RSVA6 significantly reduced the depressive-like behavior triggered by LPS in the TST and ST. Altogether, our data suggest RSVA6 as a potential drug candidate for the treatment of neuroinflammatory conditions.

Human serum albumin-resveratrol complex formation: Effect of the phenolic chemical structure on the kinetic and thermodynamic parameters of the interactions.

The thermodynamics and kinetics of binding between human serum albumin (HSA) and resveratrol (RES) or its analog (RESAn1) were investigated by surface plasmon resonance (SPR). The binding constant and the kinetic constants of association and dissociation indicated that RESAn1 has higher affinity toward HSA than does RES. The formation of these complexes was entropically driven ( [Formula: see text] , [Formula: see text]  KJ mol-1). However, for both polyphenols, the activation energy (Eact) of association (a) of free molecules was higher than that for dissociation (d) of the stable complex ( [Formula: see text]  KJ mol-1), and the rate of association was faster than that of dissociation since the activation Gibbs free energy (ΔG‡) was lower for the former (ΔGaHSA-RES‡â‰…54.73,ΔGdHSA-RES‡â‰…73.83,ΔGaHSA-RESAn1‡â‰…54.14,ΔGdHSA-RESAn1‡â‰…73.97 KJ mol-1). This study showed that small differences in the structure of polyphenols such as RES and RESAn1 influenced the thermodynamics and kinetics of the complex formation with HSA.

Novel functionalized 1,2,3-triazole derivatives exhibit antileishmanial activity, increase in total and mitochondrial-ROS and depolarization of mitochondrial membrane potential of Leishmania amazonensis.

1,2,3-triazolium salts are poorly understood regarding their antileishmanial activity. Hence, as an effort to identify novel chemical scaffolds as antileishmanial agents, a series of 1,2,3-triazolium salts (TS) and corresponding 1,2,3-triazole (T) precursors including new epoxide derivatives were synthesized and assayed against Leishmania amazonensis promastigote and intracellular amastigote forms. Among them, the compound TS-6 exhibited promising activity on promastigotes (IC50 = 3.61 µM) and intracellular amastigotes (IC50 = 7.61 µM) of L. amazonensis, superior to miltefosine (IC50 > 10.0 µM), used as reference drug. In addition, TS-6 showed negligible cytotoxicity on murine peritoneal macrophages with a SI of about 10. Studies on the mode of action of TS-6 indicate mitochondrial dysfunction through an increase in 'total' and mitochondrial-ROS as well as depolarization of mitochondrial membrane potential of L. amazonensis promastigotes. In silico physicochemical studies indicate that the TS-6 could potentially be used as an oral drug.

Resveratrol analogues present effective antileishmanial activity against promastigotes and amastigotes from distinct Leishmania species by multitarget action in the parasites.

OBJECTIVES: The in vitro antileishmanial effect of analogues of resveratrol (AR) present in the N-aryl imines and N-aryl hydrazones series was investigated. In addition, possible parasite targets were evaluated. METHODS: Antipromastigote activity of Leishmania amazonensis, L. braziliensis and L. infantum, as well as the cytotoxicity on macrophages was determined by MTT assay and L. braziliensis-infected macrophages effect by Giemsa stain. After staining, effects on the parasite targets were analysed by flow cytometry or by fluorescence microscopy. KEY-FINDINGS: Among the tested compounds, the derivative AR26 showed the best effect against promastigotes of all Leishmania species (IC50  < 3.0 µg/ml), being more active than miltefosine, the control drug. AR26 was also effective against amastigotes of L. braziliensis (IC50  = 15.9 µg/ml), with low toxicity to mammalian cells. The evaluation of mechanism of action of AR26 on L. braziliensis promastigotes indicates mitochondrial potential depolarization, plasma membrane permeabilization, interference in the progression of the cell cycle and accumulation of autophagic vacuoles. In addition, any increase of the reactive oxygen species levels was detected in the treated L. braziliensis-macrophages. CONCLUSIONS: Data indicate that the antileishmanial activity of AR26 is related to multitarget action, and the resveratrol analogues could be used in future studies as antileishmanial agent.