Synthesis, cytotoxicity and in vitro antileishmanial activity of naphthothiazoles

The leishmaniasis is a spectral disease caused by the protozoan Leishmania spp., which threatens millions of people worldwide. Current treatments exhibit high toxicity, and there is no vaccine available. The need for new lead compounds with leishmanicidal activity is urgent. Considering that many lead leishmanicidal compounds contain a quinoidal scaffold and the thiazole heterocyclic ring is found in a number of antimicrobial drugs, we proposed a hybridization approach to generate a diverse set of semi-synthetic heterocycles with antileishmanial activity. We found that almost all synthesized compounds demonstrated potent activity against promastigotes of Leishmania (Viannia) braziliensis and reduced the survival index of Leishmania amastigotes in mammalian macrophages. Furthermore, the compounds were not cytotoxic to macrophages at fivefold higher concentrations than the EC50 for promastigotes. All molecules fulfilled Lipinski's Rule of Five, which predicts efficient orally absorption and permeation through biological membranes, the in silico pharmacokinetic profile confirmed these characteristics. The potent and selective activity of semi-synthetic naphthothiazoles against promastigotes and amastigotes reveals that the 2-amino-naphthothiazole ring may represent a scaffold for the design of compounds with leishmanicidal properties and encourage the development of drug formulation and new compounds for further studies in vivo. © 2013 John Wiley & Sons A/S

The Semisynthetic Landscape of Aphidicolin: Inspiration Towards Leishmanicidal Compounds

Recent studies have shown that aphidicolin, a secondary metabolite of the endophytic fungus Nigrospora sphaerica, has high activity against the protozoan Leishmania major. Despite its promising leishmanicidal potential, aphidicolin presents a therapeutically unsuitable physico-chemical and pharmacokinetic profile. In this sense, a review of the literature shows the limited types of modification for this terpene. In addition, it gives an idea about the molecular properties of the compounds produced and which were correlated to leishmanicidal derivatives. This analysis provided us a rationale for the development of an oxime derivative. We synthesized the oxime-aphidicolin and a series of derivatives for a preliminary evaluation of the structural requirements for the leishmanicidal activity of aphidicolin and its semisynthetic derivatives. Eight compounds have been synthesized and tested against different species of the Leishmania protozoa. The preliminary evaluation demonstrated high leishmanicidal activity for aphidicolin, while the oxime derivative shows moderate selectivity for the L. braziliensis species, which is commonly found in several South American countries. None of the compounds showed cytotoxicity against mammalian cells.Recentes estudos demonstraram que afidicolina, metabólito secundário do fungo endofítico Nigrospora sphaerica, apresenta alta atividade contra o protozoário Leishmania major. Apesar do promissor potencial leishmanicida, a afidicolina apresenta propriedades físico-químicas e perfil farmacocinético inadequado para terapêutica. Neste sentido, uma revisão da literatura apresenta as limitadas modificações para este terpeno e ainda traz informações sobre as propriedades moleculares dos compostos já descritos e sua correlação com compostos leishmanicidas. Essa revisão forneceu uma análise racional para o desenvolvimento do derivado oxima. Uma série de derivados da afidicolina bem como o análogo oxima foram sintetizados para avaliação preliminar dos requisitos estruturais para atividade leishmanicida da afidicolina e seus derivados semi-sintéticos. Oito compostos foram sintetizados e testados contra diferentes espécies de Leishmania. A avaliação preliminar demonstrou alta atividade leishmanicida da afidicolina enquanto que o derivado oxima apresenta moderada seletividade contra a espécie L. braziliensis, endêmica em diversos países da América do Sul. Nenhum dos compostos apresentou citotoxicidade contra células de mamíferos

Bioactive extracts and chemical constituents of two endophytic strains of Fusarium oxysporum

Ethyl acetate extracts of cultures grown in liquid Czapek and on solid rice media of the fungal endophyte Fusarium oxysporum SS46 isolated from the medicinal plant Smallanthus sonchifolius (Poepp.) H. Rob., Asteraceae, exhibited considerable cytotoxic activity when tested in vitro against human cancer cells. Chromatographic separation yielded anhydrofusarubin (1) and beauvericin (2) that were identified based on their ¹H and 13C NMR data. Compounds 1 and 2 showed the strongest cytotoxic activity against different cancer cell lines. Compound 2 also showed promising activity against Leishmania braziliensis. Hexanic extract of F. oxysporum SS50 grown on solid rice media also afforded a mixture of compounds that displayed cytotoxic activity against different cancer cell lines. Chemical analysis of the mixture of compounds, investigated by gas chromatography-mass spectrometry (GC-MS), showed that there was a predominance of methyl esters of fatty acids and alkanes

Mycoleptones A–C and Polyketides from the EndophyteMycoleptodiscus indicus

Three new azaphilones with an unusual methylene bridge, named mycoleptones A, B, and C (2, 4, and 5), were isolated from cultures of Mycoleptodiscus indicus, a fungus associated with the South American medicinal plant Borreria verticillata. Additionally, four known polyketides, austdiol (1), eugenitin (3), 6-methoxyeugenin (6), and 9-hydroxyeugenin (7), were also isolated. The structural characterization of compounds was carried out by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, electronic circular dichroism spectroscopy, time-dependent density functional theory calculations, and X-ray crystallography. Compounds 1-9 were weakly active when tested in antileishmanial and cytotoxicity assays

Mycoleptones A–C and Polyketides from the Endophyte <i>Mycoleptodiscus indicus</i>

Three new azaphilones with an unusual methylene bridge, named mycoleptones A, B, and C (<b>2</b>, <b>4</b>, and <b>5</b>), were isolated from cultures of <i>Mycoleptodiscus indicus</i>, a fungus associated with the South American medicinal plant <i>Borreria verticillata</i>. Additionally, four known polyketides, austdiol (<b>1</b>), eugenitin (<b>3</b>), 6-methoxyeugenin (<b>6</b>), and 9-hydroxyeugenin (<b>7</b>), were also isolated. The structural characterization of compounds was carried out by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, electronic circular dichroism spectroscopy, time-dependent density functional theory calculations, and X-ray crystallography. Compounds <b>1</b>–<b>9</b> were weakly active when tested in antileishmanial and cytotoxicity assays