Patrícia A. Machado

High selective antileishmanial activity of vanadium complex with stilbene derivative

Leishmaniasis is a group of disease caused by different species of the parasite Leishmania affecting millions of people worldwide. Conventional therapy relies on multiple parenteral injections with pentavalent antimonials which exhibit high toxicity and various side effects have been reported. Hence, the research for an effective and low toxic effect drug is necessary. In the present work, the synthesis, spectroscopic and analytical characterizations of stilbene derivative (H2Salophen) and its vanadium complex (VOSalophen) are reported. Besides the chemical ancillary information, investigation of the leishmanicidal effects of these compounds were provided. The biological assays against promastigote and amastigote forms of L. amazonensis have been shown that VOSalophen exhibited a strong antiparasitic activity (IC50 of 6.65 and 3.51 μM, respectively). Furthermore, the leishmanicidal activity was concentration and time-dependent. Regarding toxicity and selectivity on mammalian cells, VOSalophen have not caused significant damage to human erythrocytes in all concentrations tested and VOSalophen was almost seven times more destructive for the intracellular parasite than for macrophages. Furthermore, the leishmanicidal activity of VOSalophen in promastigote forms of L. amazonensis could be associated to mitochondrial dysfunction and increase of the reactive oxygen species (ROS) production. In L. amazonensis-infected macrophages, VOSalophen induces ROS production and a microbicidal action NO-dependent. Our biological results indicate the effective and selective action of VOSalophen against L. amazonensis and the leishmanicidal effect can be associated to parasite disorders and immumodulatory effects.

Synthesis, cytotoxicity and antileishmanial activity of some N-(2-(indol-3-yl)ethyl)-7-chloroquinolin-4-amines.

We report herein the condensation of 4,7‐dichloroquinoline (1) with tryptamine (2) and D‐tryptophan methyl ester (3). Hydrolysis of the methyl ester adduct (5) yielded the free acid (6). The compounds were evaluated in vitro for activity against four different species of Leishmania promastigote forms and for cytotoxic activity against Kb and Vero cells. Compound (5) showed good activity against the Leishmania species tested, while all three compounds displayed moderate activity in both Kb and Vero cells.

Effect of 3‐Alkylpyridine Marine Alkaloid Analogues in Leishmania Species Related to American Cutaneous Leishmaniasis

A series of oxygenated analogues of marine 3‐alkylpyridine alkaloids were synthesized, and their leishmanicidal activity was assayed. All compounds were prepared from 3‐pyridinepropanol in few steps and in good yields. The key step for the synthesis of these compounds was a classic Williamson etherification under phase‐transfer conditions. Besides toxicity in peritoneal macrophages, the compounds exhibited a significant leishmanicidal activity. Of twelve compounds tested, five showed a strong leishmanicidal activity against promastigote forms of Leishmania amazonensis and L. braziliensis with IC50 below 10 μm. Compounds 11, 14, 15, and 16 showed a strong leishmanicidal activity on intracellular amastigotes (IC50 values of 2.78; 0.27; 1.03, and 1.33 μm, respectively), which is unlikely to be owing to the activation of nitric oxide production by macrophages.

Synthesis, Antitubercular and Leishmanicidal Evaluation of Resveratrol Analogues

In this paper we continue our efforts in the search for new Schiff bases as resveratrol analogues as promising antitubercular and antileishmanial agents. Compounds were evaluated in vitro against Mycobacterium tuberculosis and Leishmania species. Compounds showed varying activity against promastigotes of all Leishmania species tested (concentration leading to reduction of 50% of parasite growth-IC50 values ranging from 1.60 to 15.53 µg mL -1 ). Majority of compounds exhibited good results against Leishmania species with IC50 values below 10.00 µg mL -1 , with no cytotoxicity against macrophages. One of the analogues showed the best activity against amastigotes of L. amazonensis (IC50 = 5.73 µg mL -1 ). Furthermore, the compounds showed comparable or better effect than drugs commonly used in tuberculosis treatment such as Cycloserine®. The analogue that was the most active for M. tuberculosis had minimal inhibitory concentration MIC90 = 0.78 µg mL -1 . The in vitro cytotoxicity on Vero cells (CC50), as well as the selectivity index (SI = CC50/MIC) were also evaluated, and showed that the synthesized analogues are not cytotoxic.

Insights about resveratrol analogues against trypanothione reductase of Leishmania braziliensis: molecular modeling, computational docking and in vitro antileishmanial studies

Abstract In this work, we combined molecular modeling, computational docking and in vitro analysis to explore the antileishmanial effect of some resveratrol analogs (ResAn), focusing on their pro-oxidant effect. The molecular target was the trypanothione reductase of Leishmania braziliensis (LbTryR), an essential component of the antioxidant defenses in trypanosomatid parasites. Three-dimensional structures of LbTryR were modeled and molecular docking studies of ResAn1-5 compounds showed the following affinity: ResAn1 > ResAn2 > ResAn4 > ResAn5 > ResAn3. Positive correlation was observed between these compounds’ affinity to the LbTryR and the IC50 values against Leishmania sp (ResAn1 < ResAn2 < ResAn4), which allows for TryR being considered an important target for them. As the compound ResAn1 showed the best antileishmanial activity, and docking studies showed its high affinity for NADP binding site (NS) of TryR, plus having been able to induce ROS production in L. braziliensis promastigotes treated, ResAn1 probably occupies NS interfering in the electron transfer processes responsible for the catalytic reaction. The in silico prediction of ADMET properties suggests that ResAn1 may be a promising drug candidate with properties to cross biological membranes and high gastrointestinal absorption, not violating Lipinski’s rules. Ultimately, the antileishmanial effect of ResAn can be associated with a pro-oxidant effect which, in turn, can be exploited as an antimicrobial agent. Communicated by Ramaswamy H. Sarma