In vitro cytotoxic and leishmanicidal activity of isolated and semisynthetic ent-pimaranes from Aldama arenaria

Two pimaranes ent-pimara -8(14),15-dien-19-oic acid (1) and ent-8(14),15-pimaradien-3β-ol (2), isolated from Aldama arenaria, and six semi-synthetic derivatives methyl ester of the ent-pimara-8(14),15-dien-19-oic acid (3), ent-pimara-8(14),15-dien-19-ol (4), acetate of ent-pimara-8(14),15-dien-19-ol (5), ent-pimara-8(14),15-dien-19-ol succinic acid (6), acetate of ent-8(14),15-pimaradien-3β-ol (7), ent-8(14),15-pimaradien-3β-ol succinic acid (8) were evaluated in vitro for their cytotoxic activities to childhood leukemia cell lines and leishmanicidal activity against the parasite Leishmania amazonensis. Among these compounds, 1 to 6 presented moderate cytotoxic activity, with compound 4 being the most active (GI50 of 2.6 µM for the HL60 line) and the derivatives 7 and 8 inactive. Against the parasite Leishmania amazonensis, the most promising derivative was acetate of ent-pimara-8(14),15-dien-19-ol (5), with EC50 of 20.1 µM, selectivity index of 14.3, and significant reduction in the parasite load. Pimarane analogues 1, ent-pimara-8(14),15-dien-19-oic acid, and 2, ent-8(14),15-pimaradien-3β-ol, presented different activities, corroborating the application of such molecules as prototypes for the design of other derivatives that have greater cytotoxic or leishmanicidal potential.

Discovery of New Chemical Tools against Leishmania amazonensis via the MMV Pathogen Box

The protozoan parasite Leishmania causes a spectrum of diseases and there are over 1 million infections each year. Current treatments are toxic, expensive, and difficult to administer, and resistance to them is emerging. In this study, we screened the antileishmanial activity of the Pathogen Box compounds from the Medicine for Malaria Venture against Leishmania amazonensis, and compared their structures and cytotoxicity. The compounds MMV676388 (3), MMV690103 (5), MMV022029 (7), MMV022478 (9) and MMV021013 (10) exerted a significant dose-dependent inhibition effect on the proliferation of L. amazonensis promastigotes and intracellular amastigotes. Moreover, studies on the mechanism of cell death showed that compounds 3 and 5 induced an apoptotic process while the compounds 7, 9 and 10 seem to induce an autophagic mechanism. The present findings underline the potential of these five molecules as novel therapeutic leishmanicidal agents.

7,8-dihydroxyflavone-functionalized gold nanoparticles target the arginase enzyme of Leishmania donovani

Aim: To analyze the efficacy and possible mechanism of action of 7,8-dihydroxyflavone (DHF) and DHF synthesized gold nanoparticles (GNPs) against the parasite Leishmania donovani. Methods: GNPs were synthesized using DHF and characterized by dynamic light scattering, ζ potential, Fourier transform infrared spectroscopy, transmission electron microscopy and x-ray diffraction. The efficacy of DHF and DHF-GNP were tested against sensitive and drug-resistant parasites. GNP uptake was measured on macrophages by atomic absorption spectroscopy. Results: DHF and DHF-GNP (∼35 nm) were equally effective against sensitive and drug-resistant strains and inhibited the arginase activity of parasites. Increased IFN-γ and reduced IL-12 cytokine response showed a Th1/Th2-mediated cell death in macrophages. Conclusion: The low cytotoxicity and high biological activity of DHF-GNP may be useful for chemotherapy of leishmaniasis.

Alkyl-Resorcinol Derivatives as Inhibitors of GDP-Mannose Pyrophosphorylase with Antileishmanial Activities

Leishmaniasis is a vector-borne disease caused by the protozoan parasite Leishmania found in tropical and sub-tropical areas, affecting 12 million people around the world. Only few treatments are available against this disease and all of them present issues of toxicity and/or resistance. In this context, the development of new antileishmanial drugs specifically directed against a therapeutic target appears to be a promising strategy. The GDP-Mannose Pyrophosphorylase (GDP-MP) has been previously shown to be an attractive therapeutic target in Leishmania. In this study, a chemical library of 5000 compounds was screened on both L. infantum (LiGDP-MP) and human (hGDP-MP) GDP-MPs. From this screening, oncostemonol D was found to be active on both GDP-MPs at the micromolar level. Ten alkyl-resorcinol derivatives, of which oncostemonols E and J (2 and 3) were described for the first time from nature, were then evaluated on both enzymes as well as on L. infantum axenic and intramacrophage amastigotes. From this evaluation, compounds 1 and 3 inhibited both GDP-MPs at the micromolar level, and compound 9 displayed a three-times lower IC50 on LiGDP-MP, at 11 µM, than on hGDP-MP. As they displayed mild activities on the parasite, these compounds need to be further pharmacomodulated in order to improve their affinity and specificity to the target as well as their antileishmanial activity.

Prevalence of Cutaneous leishmaniasis in Khartoum State-Sudan

Cutaneous leishmaniasis is the known form of leishmaniasis affecting humans. It is a skin infection caused by the protozoan parasite Leishmania from animals to humans by the bite of a vector phlebotomine sandfly. About 21 species causing leishmaniasis depending on geographical distribution and host immunity. Populations of northern areas of Sudan are commonly affected by the disease.

The In Silico Identification of Potential Members of the Ded1/DDX3 Subfamily of DEAD-Box RNA Helicases from the Protozoan Parasite Leishmania infantum and Their Analyses in Yeast

DEAD-box RNA helicases are ubiquitous proteins found in all kingdoms of life and that are associated with all processes involving RNA. Their central roles in biology make these proteins potential targets for therapeutic or prophylactic drugs. The Ded1/DDX3 subfamily of DEAD-box proteins is of particular interest because of their important role(s) in translation. In this paper, we identified and aligned the protein sequences of 28 different DEAD-box proteins from the kinetoplast-protozoan parasite Leishmania infantum, which is the cause of the visceral form of leishmaniasis that is often lethal if left untreated, and compared them with the consensus sequence derived from DEAD-box proteins in general, and from the Ded1/DDX3 subfamily in particular, from a wide variety of other organisms. We identified three potential homologs of the Ded1/DDX3 subfamily and the equivalent proteins from the related protozoan parasite Trypanosoma brucei, which is the causative agent of sleeping sickness. We subsequently tested these proteins for their ability to complement a yeast strain deleted for the essential DED1 gene. We found that the DEAD-box proteins from Trypanosomatids are highly divergent from other eukaryotes, and consequently they are suitable targets for protein-specific drugs.

The Leishmania donovani SENP Protease Is Required for SUMO Processing but Not for Viability

The protozoan parasite Leishmania donovani is part of an early eukaryotic branch and depends on post-transcriptional mechanisms for gene expression regulation. This includes post-transcriptional protein modifications, such as protein phosphorylation. The presence of genes for protein SUMOylation, i.e., the covalent attachment of small ubiquitin-like modifier (SUMO) polypeptides, in the Leishmania genomes prompted us to investigate the importance of the sentrin-specific protease (SENP) and its putative client, SUMO, for the vitality and infectivity of Leishmania donovani. While SENP null mutants are viable with reduced vitality, viable SUMO null mutant lines could not be obtained. SUMO C-terminal processing is disrupted in SENP null mutants, preventing SUMO from covalent attachment to proteins and nuclear translocation. Infectivity in vitro is not affected by the loss of SENP-dependent SUMO processing. We conclude that SENP is required for SUMO processing, but that functions of unprocessed SUMO are critical for Leishmania viability.