Adriana Oliveira dos Santos

Recent advances in leishmaniasis treatment

About 1.5 million new cases of cutaneous leishmaniasis and 500,000 new cases of visceral leishmaniasis occur each year around the world. For over half a century, the clinical forms of the disease have been treated almost exclusively with pentavalent antimonial compounds. In this review, we describe the arsenal available for treating Leishmania infections, as well as recent advances from research on plants and synthetic compounds as source drugs for treating the disease. We also review some new drug-delivery systems for the development of novel chemotherapeutics. We observe that the pharmaceutical industry should employ its modern technologies, which could lead to better use of plants and their extracts, as well as to the development of synthetic and semi-synthetic compounds. New studies have highlighted some biopharmaceutical technologies in the design of the delivery strategy, such as nanoparticles, liposomes, cochleates, and non-specific lipid transfer proteins. These observations serve as a basis to indicate novel routes for the development and design of effective anti-Leishmania drugs.

Effect of Elatol, Isolated from Red Seaweed Laurencia dendroidea, on Leishmania amazonensis

In the present study, we investigated the antileishmanial activity of sesquiterpene elatol, the major constituent of the Brazilian red seaweed Laurencia dendroidea (Hudson) J.V. Lamouroux, against L. amazonensis. Elatol after 72 h of treatment, showed an IC50 of 4.0 μM and 0.45 μM for promastigote and intracellular amastigote forms of L. amazonensis, respectively. By scanning and transmission electron microscopy, parasites treated with elatol revealed notable changes compared with control cells, including: pronounced swelling of the mitochondrion; appearance of concentric membrane structures inside the organelle; destabilization of the plasma membrane; and formation of membrane structures, apparently an extension of the endoplasmic reticulum, which is suggestive of an autophagic process. A cytotoxicity assay showed that the action of the isolated compound is more specific for protozoa, and it is not toxic to macrophages. Our studies indicated that elatol is a potent antiproliferative agent against promastigote and intracellular amastigote forms, and may have important advantages for the development of new anti-leishamanial chemotherapies.

4-Acetoxydolastane Diterpene from the Brazilian Brown Alga Canistrocarpus cervicornis as Antileishmanial Agent

Natural marine products have shown an interesting array of diverse and novel chemical structures with potent biological activities. Our study reports the antiproliferative assays of crude extracts, fraction and pure compound (4R,9S,14S)-4α-acetoxy-9β,14α-dihydroxydolast-1(15),7-diene (1) obtained from brown alga Canistrocarpus cervicornis showing the antileishmanial activity. We showed that 1 had a dose-dependent activity during 72 h of treatment, exhibiting IC50 of 2.0 μg/mL, 12.0 μg/mL, and 4.0 μg/mL for promastigote, axenic amastigote and intracellular amastigote forms of Leishmania amazonensis, respectively. A cytotoxicity assay showed that the action of the isolated compound 1 was 93.0 times less toxic to the macrophage than to the protozoan. Additionally, compound 1 induced ultrastructural changes, including extensive mitochondrial damage; decrease in Rh123 fluorescence, suggesting interference with the mitochondrial membrane potential; and lipid peroxidation in parasite cells. The use of 1 from C. cervicornis against L. amazonensis parasites might be of great interest as a future alternative to the development of new antileishmanial drugs.

Effects of (-) mammea A/BB isolated from Calophyllum brasiliense leaves and derivatives on mitochondrial membrane of Leishmania amazonensis.

We have previously demonstrated antileishmanial activity on Leishmania amazonensis of the natural (1-2), synthetic (7) and derivatives of coumarin (-) mammea A/BB (3-6) isolated from the dichloromethane extract of Calophyllum brasiliense leaves. The aim of the present study was to evaluate morphological and ultrastructural alterations in Leishmania amazonensis induced by these compounds. In promastigote forms, all seven compounds produced significant morphological and ultrastructural alterations, as revealed by scanning and transmission electron microscopy. The compound 5,7-dihydroxy-8-(2-methylbutanoyl)-6-(3-methylbutyl)-4-phenyl-chroman-2-one (3), the most active antileishmanial with LD₅₀ of 0.9 μM), induced cell shrinkage and a rounded appearance of the cells. Parasites incubated in the presence of compound (3) showed ultrastructural changes, such as the appearance of mitochondrial swelling with a reduction in the density of the mitochondrial matrix and the presence of vesicles inside the mitochondrion, indicating damage and significant change in this organelle; abnormal chromatin condensation, alterations in the nuclear envelope, intense atypical cytoplasmic vacuolization, and the appearance of autophagic vacuoles were also observed. In addition, the compound (3) may be acting to depolarize the mitochondrial membrane potential of the cells, leading to death of the parasite.

Copaiba Oil: An Alternative to Development of New Drugs against Leishmaniasis

Leishmaniasis is a neglected disease that is increasing globally at an alarming rate. Glucantime has been the therapy of choice for more than 50 years. A recent study reported the antileishmanial activity of copaiba oil against Leishmania amazonensis. These results led us to investigate morphological and ultrastructural changes in L. amazonensis treated with copaiba oil, using electron microscopy and flow cytometry to assess specific organelles as targets for copaiba oil. In the promastigote and axenic amastigote forms, this copaiba oil caused notable morphological and ultrastructural changes, including extensive mitochondrial damage and denaturation of the plasma membrane. Copaiba oil treatment also induced a decrease in Rh123 fluorescence, suggesting interference with the mitochondrial membrane potential and loss of cell viability with an increase in plasma membrane permeability, as observed by flow cytometry after staining with propidium iodide. In conclusion, copaiba oil could be exploited for the development of new antileishmanial drugs.

Atividade antileishmania do extrato hidroalcoólico e de frações obtidas de folhas de Piper regnellii (Miq.) C. DC. var. pallescens (C. DC.) Yunck

Biological activity of the crude extract and several fractions obtained from Piper regnellii var. pallescens was assessed on Leishmania amazonensis. This study included the extraction process and bioassay-guided fractionation by the adsorption chromatography method. A progressive increase in the antileishmanial effect was observed in the course of the purification process. The hydroalcoholic extract water soluble (EBA) had a 50% inhibitory concentration (IC50) at 167 µg/mL whereas the hydroalcoholic extract acetate soluble (EBAcOEt) showed an IC50 of 30 µg/mL against the growth of promastigote forms after 48 h of culturing. The hexan fraction (FHex) showed an antileishmanial activity greater than EBAcOEt with IC50 at 21.5 µg/mL. Analysis of cytotoxicity indicated that the toxic concentrations of the EBA, EBAcOEt, and fractions were higher for J774G8 macrophages than for the protozoans.