Antileishmanial activity of a naphthoquinone derivate against promastigote and amastigote stages of Leishmania infantum and Leishmania amazonensis and its mechanism of action against L. amazonensis species.

Leishmaniasis has become a significant public health issue in several countries in the world. New products have been identified to treat against the disease; however, toxicity and/or high cost is a limitation. The present work evaluated the antileishmanial activity of a new naphthoquinone derivate, Flau-A [2-(2,3,4-tri-O-acetyl-6-deoxy-ß-L-galactopyranosyloxy)-1,4-naphthoquinone], against promastigote and amastigote-like stages of Leishmania amazonensis and L. infantum. In addition, the cytotoxicity in murine macrophages and human red cells was also investigated. The mechanism of action of Flau-A was assessed in L. amazonensis as well as its efficacy in treating infected macrophages and inhibiting infection of pretreated parasites. Results showed that Flau-A was effective against promastigotes and amastigote-like forms of both parasite species, as well as showed low toxicity in mammalian cells. Results also highlighted the morphological and biochemical alterations induced by Flau-A in L. amazonensis, including loss of mitochondrial membrane potential, as well as increased reactive oxygen species production, cell shrinkage, and alteration of the plasma membrane integrity. The present study demonstrates for the first time the antileishmanial activity of Flau-A against two Leishmania species and suggests that the mitochondria of the parasites may be the main target organelle. Data shown here encourages the use of this molecule in new studies concerning treatment against Leishmania infection in mammalian hosts.

Novel steroid derivatives: synthesis, antileishmanial activity, mechanism of action, and in silico physicochemical and pharmacokinetics studies.

The search for new drugs for the treatment of leishmaniasis is an important strategy for improving the current therapeutic arsenal for the disease. There are several limitations to the available drugs including high toxicity, low efficacy, prolonged parenteral administration, and high costs. Steroids are a diverse group of compounds with various applications in pharmacology. However, the antileishmanial activity of this class of molecules has not yet been explored. Therefore, in the present study, we investigated the antileishmanial activity and cytotoxicity of novel steroids against murine macrophages with a focus on the derivatives of cholesterol (CD), cholic acid (CA), and deoxycholic acid (DA). Furthermore, the mechanism of action of the best compound was assessed, and in silico studies to evaluate the physicochemical and pharmacokinetic properties were also conducted. Among the sixteen derivatives, schiffbase2, CD2 and deoxycholic acid derivatives (DOCADs) were effective against promastigotes of Leishmania species. Despite their low toxicity to macrophages, the majority of DOCADs were active against intracellular amastigotes of L. amazonensis, and DOCAD5 exhibited the best biological effect against these parasitic stages (IC50 = 15.34 µM). Neither the CA derivatives (CAD) nor DA alone inhibited the intracellular parasites. Thus, the absence of hydroxyl in the C-7 position of the steroid nucleus, as well as the modification of the acid group in DOCADs were considered important for antileishmanial activity. The treatment of L. amazonensis promastigote forms with DOCAD5 induced biochemical changes such as depolarization of the mitochondrial membrane potential, increased ROS production and cell cycle arrest. No alterations in parasite plasma membrane integrity were observed. In silico physicochemical and pharmacokinetic studies suggest that DOCAD5 could be a good candidate for an oral drug. The data demonstrate the potential antileishmanial effect of certain steroid derivatives and encourage new in vivo studies.

Novel organic salts based on quinoline derivatives: The in vitro activity trigger apoptosis inhibiting autophagy in Leishmania spp.

Leishmaniases are infectious diseases, caused by protozoa of the Leishmania genus. These drugs present high toxicity, long-term administration, many adverse effects and are expensive, besides the identification of resistant parasites. In this work, the antileishmanial activity of quinoline derivative salts (QDS) was evaluated, as well as the toxicity on mammalian cells and the mechanism of action of the most promising compound. Among the compound tested, only the compound QDS3 showed activity against promastigotes and amastigotes of Leishmania spp., being more active against the intracellular amastigotes of L. amazonensis-GFP (IC50 of 5.48 µM). This value is very close to the one observed for miltefosine (IC50 of 4.05 µM), used as control drug. Furthermore, the compound QDS3 exhibited a selective effect, being 40.35 times more toxic to the amastigote form than to the host cell. Additionally, promastigotes of L. amazonensis treated with this compound exhibited characteristics of cells in the process of apoptosis such as mitochondrial membrane depolarization, mitochondrial swelling, increase of ROS production, phosphatidylserine externalization, reduced and rounded shape, and cell cycle alteration. The integrity of the plasma membrane remained unaltered, excluding necrosis in treated promastigotes. The compound QDS3 inhibited the formation of autophagic vacuoles, which may have contributed to parasite death by preventing autophagic mechanisms in the removal of damaged organelles, intensifying the damage caused by the treatment, highlighting the antileishmanial effect of this compound. In addition, treatment with QDS3 induced increased ROS levels in L. amazonensis-infected macrophages, but not in uninfected host cell. These data reinforce that the induction of oxidative stress is one of the main toxic effects caused by the treatment with the compound QDS3 in L. amazonensis, causing irreversible damage and triggering a selective death of intracellular parasites. Data shown here confirm the biological activity of quinoline derivatives and encourage future in vivo studies with this compound in the murine model.

Studies with emulsion containing trans-resveratrol: in vitro release profile and ex vivo human skin permeation.

Resveratrol is a phenolic compound that has been widely studied in the last years because of its extensive pharmacological properties. It also has physicochemical properties that are adequate for diffusion through the human skin. An analytical method by high performance liquid chromatography was developed and validated for its determination in transdermal emulsion, as well in receptor media and skin layers. The trans-resveratrol release kinetic followed the Higushi's model (R(2) = 0.9926) with steady-state diffusion flux and lag time of 138.5 µg cm(-2) h(-1) and 0.49 h, respectively. It showed a percentage at 64.96 % for permeation. Thus, the results suggest that the emulsion studied is a potential vehicle for transresveratrol administration by transdermal route.