Wilson Cardona

Five new steroids from Solanum nudum

Abstract Five new steroids, the cholest-4-ene-3,22-diones: tumacone A ( 1 ), tumacone B ( 2 ), tumacoside A ( 3 ), tumacoside B ( 4 ), and a furostenone: tumaquenone ( 5 ), besides diosgenone ( 6 ), were isolated from the aerial parts of Solanum nudum . Their structures were determined by 2D NMR, MS analyses and chemical correlations. Steroid 3 and 5 displayed in vitro antimalarial activity against a Plasmodium falciparum chloroquine-resistant FCB-1 strain (IC 50 27 and 16 μM). The observed stereodependent cyclization into spiroketals of two 16-O isomers is discussed.

Synthesis, leishmanicidal, trypanocidal and cytotoxic activity of quinoline-hydrazone hybrids

Cutaneous leishmaniasis and Chagas disease are vector-borne parasitic disease causing serious risks to million people living in poverty-stricken areas. Both diseases are a major health problem in Latin America, and currently drugs for the effective treatment of these diseases have important concerns related with efficacy or toxicity than need to be addressed. We report herein the synthesis and biological activities (cytotoxicity, leishmanicidal and trypanocidal activities) of ten quinolone-hydrazone hybrids. The structure of the products was elucidated by spectrometric analyses. The synthesized compounds were evaluated against amastigotes forms of L. (V) panamensis which is the most prevalent Leishmania species in Colombia and Trypanosoma cruzi that is the major pathogenic species to humans; in turn, cytotoxicity was evaluated against human U-937 macrophages. Compounds 6b, 6c and 8 showed activity against L. (V) panamensis with EC50 of 6.5 ± 0.8 μg/mL (21.2 μM), 0.8 ± 0.0 μg/mL (2.6 μM) and 3.4 ± 0.6 μg/mL (11.1 μM), respectively, while compounds 6a and 6c had activity against T. cruzi. with EC50 values of 1.4 ± 0.3 μg/mL (4.8 μM) and 6.6 ± 0.3 μg/mL (4.6 μM), respectively. Even compound 6a showed better activity against T. cruzi than the standard drug benznidazole with EC50 = 10.5 ± 1.8 μg/mL (40.3 μM). Analysis of the results obtained against leishmaniasis indicates that antiparasite activity is related to the presence of 2-substituted quinoline (isoquinolinic core) and the hydroxyl group in positions 3 and 4 of the aromatic ring. Although the majority of these compounds were highly cytotoxic, the antiparasite activity was higher than cytotoxicity and therefore, they still have potential to be considered as hit molecules for leishmanicidal and trypanocidal drug development.

Synthesis and leishmanicidal activity of cinnamic acid esters: structure–activity relationship

Several cinnamic acid esters were obtained via Fischer esterification of cinnamic acids derivatives with aliphatic alcohols. Structures of the products were elucidated by spectroscopic analysis. The synthesized compounds were evaluated for antileishmanial activity against L. (V) panamensis amastigotes and cytotoxic activity was evaluated against mammalian U-937 cells. The compounds 11, 15–17, and 23, were active against Leishmania parasite and although toxic for mammalian cells, they still are potential candidates for antileishmanial drug development. A SAR analysis indicates that first, while smaller alkyl chains lead to higher selectivity indices (10, 11 vs. 12–17); second, the degree of oxygenation is essential for activity, primarily in positions 3 and 4 (17 vs. 18–20 and 22); and third, hydroxyl groups increase both activity and cytotoxicity (14 vs. 23). On the other hand, the presence of a double bond in the side chain is crucial for cytotoxicity and leishmanicidal activity (12 vs. 21). However, further studies are required to optimize the structure of the promising molecules and to validate the in vitro activity against Leishmania demonstrated here with in vivo studies.

Reactivity of δ-substituted α,β-unsaturated cyclic lactones with antileishmanial activity

The present study examines a set of 43 compounds for their antileishmanial activities and cytotoxicities. Negative lowest unoccupied molecular orbitas and similar values for the electrophilic Fukui function condensed at the β-position for a subset of δ-substituted α,β-unsaturated cyclic lactones classify them as strong Michael acceptors. There was a well-defined trend of increasing antileishmanial activity with increasing cytotoxicity and large selectivity indices for the most active compounds. Softer compounds were more active than harder ones as observed from the experimental data and rationalised by calculated reactivity indices.

SYNTHESIS AND LEISHMANICIDAL ACTIVITY OF NEW BIS-ALKYLQUINOLINES

ABSTRACT Bis-alkylquinolines 1-6 were synthetized via Williamson reaction between 8-hydroxyquinaldine with different 1,ω-dihaloalkanes. Structures of all the products were elucidated by spectroscopic analysis. Cytotoxic and antileishmanial activities of synthesized compounds were determinated on U-937 cells and L. (V) panamensis amastigotes, respectively. Compound 5 , 1,9-bis[(2-methylquinolin-8-yl)oxy]nonane , was the most selective against axenic and intracellular amastigotes (EC 50 = 11.3 and 22.6, μg/mL), with selectivity indices greater than 17.7 and 8.8, respectively; which makes this compound promising for the developing of new leishmanicidal drugs. Keywords: Leishmania, antiprotozoal, quinoline. e-mail: wcardona@matematicas.udea.edu.co INTRODUCTION Leishmaniasis is one of the world’s most neglected diseases, affecting largely the poorest of the poor, mainly in developing countries; 350 million people are considered at risk of contracting leishmaniasis, and around 2 million new cases occur yearly

Synthesis, leishmanicidal, trypanocidal and cytotoxic activities of quinoline-chalcone and quinoline-chromone hybrids

We report herein the synthesis and biological activities (cytotoxicity, leishmanicidal and trypanocidal) of six quinoline-chalcone and five quinoline-chromone hybrids. The synthesized compounds were evaluated against amastigotes forms of Leishmania (V) panamensis, which is the most prevalent Leishmania species in Colombia and Trypanosoma cruzi, which is the major pathogenic species to humans. Cytotoxicity was evaluated against human U-937 macrophages. Compounds 8–12, 20, 23 and 24 showed activity against Leishmania (V) panamensis, while compounds 9, 10, 12, 20 and 23 had activity against Trypanosoma cruzi with EC50 values lower than 18 mg mL−1. 20 was the most active compound for both Leishmania (V) panamensis and Trypanosoma cruzi with EC50 of 6.11 ± 0.26 μg mL−1 (16.91 μM) and 4.09 ± 0.24 (11.32 μM), respectively. All hybrids compounds showed better activity than the anti-leishmanial drug meglumine antimoniate. Compounds 20 and 23 showed higher activity than benznidazole, the current anti-trypanosomal drug. Although these compounds showed toxicity for mammalian U-937 cells,they still have the potential to be considered as candidates to antileishmanial or trypanocydal drug development.

Inversion of the stereochemical configuration (3S, 5S)-clavaminic acid into (3R, 5R)-clavulanic acid: A computationally-assisted approach based on experimental evidence

Clavulanic acid (CA), a potent inhibitor of β-lactamase enzymes, is produced by Streptomyces clavuligerus (Sc) cultivation processes, for which low yields are commonly obtained. Improved knowledge of the clavam biosynthetic pathway, especially the steps involved in the inversion of 3S-5S into 3R-5R stereochemical configuration, would help to eventually identify bottlenecks in the pathway. In this work, we studied the role of acetate in CA biosynthesis by a combined continuous culture and computational simulation approach. From this we derived a new model for the synthesis of N-acetyl-glycyl-clavaminic acid (NAG-clavam) by Sc. Acetylated compounds, such as NAG-clavam and N-acetyl-clavaminic acid, have been reported in the clavam pathway. Although the acetyl group is present in the β-lactam intermediate NAG-clavam, it is unknown how this group is incorporated. Hence, under the consideration of the experimentally proven accumulation of acetate during CA biosynthesis, and the fact that an acetyl group is present in the NAG-clavam structure, a computational evaluation of the tentative formation of NAG-clavam was performed for the purpose of providing further understanding. The proposed reaction mechanism consists of two steps: first, acetate reacts with ATP to produce a reactive acylphosphate intermediate; second, a direct nucleophilic attack of the terminal amino group of N-glycyl-clavaminic on the carbonyl carbon of the acylphosphate intermediate leads to a tetrahydral intermediate, which collapses and produces ADP and N-acetyl-glycyl-clavaminic acid. The calculations suggest that for the proposed reaction mechanism, the reaction proceeds until completion of the first step, without the direct action of an enzyme, where acetate and ATP are involved. For this step, the computed activation energy was ≅2.82kcal/mol while the reaction energy was ≅2.38kcal/mol. As this is an endothermic chemical process with a relatively small activation energy, the reaction rate should be considerably high. The calculations offered in this work should not be considered as a definite characterization of the potential energy surface for the reaction between acetate and ATP, but rather as a first approximation that provides valuable insight about the reaction mechanism. Finally, a complete route for the inversion of the stereochemical configuration from (3S, 5S)-clavaminic acid into (3R, 5R)-clavulanic acid is proposed, including a novel alternative for the double epimerization using proline racemase and NAG-clavam formation.

Synthesis and antiprotozoal activity of furanchalcone–quinoline, furanchalcone–chromone and furanchalcone–imidazole hybrids

We report herein the synthesis and biological activities (cytotoxicity, leishmanicidal, and trypanocidal) of several furanchalcone–quinoline, furanchalcone–chromone, and furanchalcone–imidazole hybrids. The synthesized compounds were evaluated against amastigotes forms of L. (V) panamensis, which is the most prevalent Leishmania species in Colombia and against Trypanosoma cruzi, which is the major pathogenic species to humans. Cytotoxicity was evaluated against human U-937 macrophages. Compounds (6e, 8a–8f, 11b, and 11c) were active against both L. (V) panamensis and T. cruzi being 8e and 8f the most active compounds with an EC50 of 0.78 and 2.16 µM against L. (V) panamensis, respectively, and 0.66 and 0.72 µM against T. cruzi, respectively. Seven hybrid compounds showed better activity than meglumine antimoniate and the anti-trypanosomal activity of nine compounds were higher than benznidazole. Although these compounds showed toxicity for mammalian U-937 cells, they still have the potential to be considered as candidates for antileishmanial or trypanocydal drug development. There is not a clear relationship between the antiprotozoal activity and the length of the alkyl linker. However, we obtained higher bioactivity when the alkyl linker has nine and twelve carbon atoms. Furanchalcone-imidazole hybrids were the most active of all compounds, showing that the imidazole salt moiety is important for their biological actions.