Modes of action of arjunolic acid and derivatives on Trypanosoma cruzi cells.

Chagas disease causes considerable morbimortality in the Americas, with circa 7 to 8 million infected people, causing at least 12,000 annual deaths and 100 million people at risk. Its chemotherapy is poorly selective and effective, associated to severe side effects and unresponsive cases. Thus, R&D on therapeutic alternatives is undoubtedly required. The Brazilian poorly studied biodiversity offers uncountable bioagents, which may be exploited for chemotherapy. The triterpene arjunolic acid (AA), reduced the Trypanosoma cruzi epimastigote in vitro proliferation with an apparent IC50 of 171 µM. Electron microscopy analysis revealed remarkable effects on the parasite surface and architecture. AA-treated parasites displayed minutely corrugated plasma membranes devoid of subpellicular microtubules as well as biogenesis of multiple basal bodies. As the AA effects appeared mainly restricted or originated at the parasite peripheral cytoplasm, including the cytoskeleton membrane linkage, we inferred that the compound targeted primarily the lipid bilayer; therefore, we performed synthetic modification to increase the molecule lipophilicity and thus membrane permeability. The methyl ester (MeAA) and tri-acetylated derivatives (3AcAA) had potentiated trypanocidal activity, producing IC50 values of 21.9 and 15.8 µM, respectively. Both derivatives were able to produce remarkable ultrastructural alterations in the parasites, including inner compartments such as Golgi apparatus and the endocytic/autophagic pathway. Parasites cultured with both derivatives displayed numerous and large autophagic vacuoles, altered flagellar length and cell body connection. These data indicate that synthetically-modified natural products comprise valuable tools in antiparasitic chemotherapy and that electron microscopy may be useful not only in determining the mechanisms of action but also in directing such modifications for rational drug design.

Effects of seco-steroids purified from Physalis angulata L., Solanaceae, on the viability of Leishmania sp / Efeitos de seco-esteróides purificados de Physalis angulata L., Solanaceae na viabilidade de Leishmania sp

Physalis angulata L., Solanaceae, is an annual herb commonly used in popular medicine in many tropical and subtropical countries. P. angulata extracts contain a variety of substances, but little is known about their pharmacological activities. In this work we investigated the in vitro antileishmanial activity of seco-steroids (physalins) purified from P. angulata. Addition of physalins B, F, and G caused a concentration-dependent inhibition in the growth of L. amazonensis promastigotes, being the IC50 values were 6.8, 1.4, and 9.2 μM, respectively. Physalin D was less active and had an IC50 value of 30.5 μM. Physalins were also active in cultures of other Leishmania species (L. major, L. braziliensis, and L. chagasi). Our results demonstrate the potent antileishmanial activity of physalins in cultures of Leishmania species of the New and Old Worlds and suggest the therapeutic potential of these seco-steroids in leishmaniasis.

Physalis angulata L., Solanaceae, é uma erva anual utilizada na medicina popular em muitos países tropicais e subtropicais. Apesar dos extratos da P. angulata apresentarem uma grande variedade de substâncias, pouco é conhecido sobre a sua atividade farmacológica. Neste trabalho foi investigado a atividade antileishmania in vitro de seco-esteroides (fisalinas) purificados da P. angulata. O tratamento com as fisalinas B, F e G causou uma inibição concentração-dependente do crescimento de promastigotas de Leishmania amazonensis em cultura axênica, com valores de IC50 de 6,8, 1,4, e 9,2 μM respectivamente. A fisalina D foi menos ativa, com valores de IC50 de 30,5 μM. Foi também observada uma atividade leishmanicida em culturas de outras espécies de Leishmania (L. major, L. braziliensis e L. chagasi). Nossos resultados demonstram que as fisalinas inibem o crescimento dos promastigotas com o tratamento de espécies de Leishmania do Velho e do Novo Mundos e sugerem o potencial terapêutico destas moléculas na leishmaniose.

Design, synthesis and cruzain docking of 3-(4-substituted-aryl)-1,2,4-oxadiazole-N-acylhydrazones as anti-Trypanosoma cruzi agents.

Research in recent years has demonstrated that the Trypanosoma cruzi cysteine protease cruzain (TCC) is a valid chemotherapeutic target, since inhibitors of this protease affect the pathology appropriately. By exploring the N-acylhydrazones (NAH) as privileged structures usually present in antiparasitic agents, we investigated a library of 16 NAH bearing the 3-(4-substituted-aryl)-1,2,4-oxadiazole scaffold (NAH 3a-h, 4a-h). The in vitro bioactivity against epimastigote and trypomastigote forms of T. cruzi was evaluated, and some NAH under study exhibited antitrypanosomal activity at concentrations that are not toxic to mammalian cells. The series of compounds based on the 3-(4-substituted-aryl)-1,2,4-oxadiazole scaffold revealed the remarkable importance of each substituent at the phenyl's 4-position for the inhibitory activity. Non-nitrated compounds 3a and 4e were found to be as potent as the reference drug, Benznidazole. In addition, the molecular origin of the antitrypanosomal properties for these series was investigated using docking studies of the TCC structure.

Activity of physalins purified from Physalis angulata in in vitro and in vivo models of cutaneous leishmaniasis.

OBJECTIVES: We have previously demonstrated the immunomodulatory effects of physalins, secosteroids purified from Physalis angulata. Here we investigate the antileishmanial activity of physalins in vitro and in vivo in a model of cutaneous leishmaniasis. METHODS: The antileishmanial activity of physalins B, D and F was tested in Leishmania-infected macrophage cultures. For the in vivo studies, BALB/c mice were infected with Leishmania amazonensis subcutaneously in the ear pinna and treated with physalin F by topical administration. RESULTS: Physalins B and F were able to reduce the percentage of Leishmania-infected macrophages and the intracellular parasite number in vitro at concentrations non-cytotoxic to macrophages. More importantly, topical treatment with physalin F significantly reduced the lesion size, the parasite load and histopathological alterations in BALB/c mice infected with L. amazonensis. CONCLUSIONS: Our results demonstrate the potent antileishmanial activity of physalins, especially physalin F, and suggest these molecules as the basis for the development of new therapeutic options for cutaneous leishmaniasis.