RESUMO
During the last years, the progression to control malaria disease seems to be slowed and WHO (World Health Organization) reported a modeling analysis with the prediction of the increase in malaria morbidity and mortality in sub-Saharan Africa during the COVID-19 pandemic. A rapid way to the discovery of new drugs could be carried out by performing investigations to identify drugs based on repurposing of "old" drugs. The 5-nitrothiazole drug, Nitazoxanide was shown to be active against intestinal protozoa, human helminths, anaerobic bacteria, viruses, etc. In this work, Nitazoxanide and analogs were prepared using two methodologies and evaluated against P. falciparum 3D7. A bithiazole analog, showed attractive inhibitory activity with an EC50 value of 5.9 µM, low propensity to show toxic effect against HepG2 cells at 25 µM, and no cross-resistance with standard antimalarials.
RESUMO
The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin's antiparasitic activities were assessed against both the epimastigote (IC50 value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC50 value of 9 ± 2 µM), as well as against P. falciparum (IC50 value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC50 > 50 µM) and peritoneal macrophage (CC50 = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development.
Assuntos
Antibacterianos/farmacologia , Antiprotozoários/farmacologia , Ascomicetos/química , Macrófagos Peritoneais/citologia , Xantonas/farmacologia , Animais , Antibacterianos/química , Antiprotozoários/química , Produtos Biológicos/química , Produtos Biológicos/farmacologia , Biomassa , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Cromatografia Líquida de Alta Pressão , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Células Hep G2 , Humanos , Macrófagos Peritoneais/efeitos dos fármacos , Macrófagos Peritoneais/parasitologia , Espectroscopia de Ressonância Magnética , Camundongos , Camundongos Endogâmicos BALB C , Testes de Sensibilidade Microbiana , Estrutura Molecular , Plasmodium falciparum/efeitos dos fármacos , Trypanosoma cruzi/efeitos dos fármacos , Xantonas/químicaRESUMO
BACKGROUND: Artemisinin-based combination therapy (ACT) is used as the first-line treatment of uncomplicated malaria caused by the Plasmodium falciparum parasite and chloroquine-resistant Plasmodium vivax parasites. Evidence of resistance to ACT has been reported in Cambodia, and without new and effective anti-malarial agents, malaria burden and mortality will rise. METHODS: The used MolPrint 2D fingerprints and the Tanimoto similarity index were used to perform a structural similarity search within the Malaria Box collection to select diverse molecular scaffolds that are different from artesunate. Next, the inhibitory potency against the P. falciparum 3D7 strain (SYBR Green I inhibition assay) and the cytotoxicity against HepG2 cells (MTT and neutral red assays) were evaluated. Then, the speed of action, the combination profile of selected inhibitors with artesunate, and the P. berghei in vivo activity of the best compounds were assessed. RESULTS: A set of 11 structurally diverse compounds from the Malaria Box with a similarity threshold of less than 0.05 was selected and compared with artesunate. The in vitro inhibitory activity of each compound confirmed the reported potencies (IC50 values ranging from 0.005 to 1 µM). The cytotoxicity of each selected compound was evaluated and used to calculate the selectivity index (SI values ranging from 15.1 to 6100). Next, both the speed of action and the combination profile of each compound with artesunate was assessed. Acridine, thiazolopyrimidine, quinoxaline, benzimidazole, thiophene, benzodiazepine, isoxazole and pyrimidoindole derivatives showed fast in vitro inhibitory activity of parasite growth, whereas hydrazinobenzimidazole, indenopyridazinone and naphthalenone derivatives were slow-acting in vitro inhibitors. Combinatory profile evaluation indicated that thiazolopyrimidinone and benzodiazepine derivatives have an additive profile, suggesting that the combination of these inhibitors with artesunate is favourable for in vitro inhibitory activity. The remaining compounds showed an antagonistic combinatory profile with artesunate. The collected data indicated that the indenopyridazinone derivative, a bc1 complex inhibitor, had a similar association profile in combination with proguanil when compared to atovaquone combined with proguanil, thereby corroborating the correlation between the molecular target and the combination profile. Lastly, the in vivo activity of the thiazolopyrimidinone and benzodiazepine derivatives were assessed. Both compounds showed oral efficacy at 50 mg/kg in a mouse model of Plasmodium berghei malaria (64% and 40% reduction in parasitaemia on day 5 post-infection, respectively). CONCLUSIONS: The findings in this paper shed light on the relationship among the speed of action, molecular target and combinatory profile and identified new hits with in vivo activity as candidates for anti-malarial combination therapy.
Assuntos
Antimaláricos/farmacologia , Artesunato/farmacologia , Combinação de Medicamentos , Plasmodium berghei/efeitos dos fármacos , Plasmodium falciparum/efeitos dos fármacos , Antimaláricos/toxicidade , Artesunato/toxicidade , Células Hep G2 , Humanos , Malária Falciparum/prevenção & controle , Testes de ToxicidadeRESUMO
We describe herein the design and synthesis of N-phenyl phthalimide derivatives with inhibitory activities against Plasmodium falciparum (sensitive and resistant strains) in the low micromolar range and noticeable selectivity indices against human cells. The best inhibitor, 4-amino-2-(4-methoxyphenyl)isoindoline-1,3-dione (10), showed a slow-acting mechanism similar to that of atovaquone. Enzymatic assay indicated that 10 inhibited P. falciparum cytochrome bc 1 complex. Molecular docking studies suggested the binding mode of the best hit to Qo site of the cytochrome bc 1 complex. Our findings suggest that 10 is a promising candidate for hit-to-lead development.
RESUMO
We report the discovery of marinoquinoline (3 H-pyrrolo[2,3- c]quinoline) derivatives as new chemotypes with antiplasmodial activity. We evaluated their inhibitory activities against P. falciparum and conducted a structure-activity relationship study, focusing on improving their potency and maintaining low cytotoxicity. Next, we devised quantitative structure-activity relationship (QSAR) models, which we prospectively validated, to discover new analogues with enhanced potency. The most potent compound, 50 (IC503d7 = 39 nM; IC50K1 = 41 nM), is a fast-acting inhibitor with dual-stage (blood and liver) activity. The compound showed considerable selectivity (SI > 6410), an additive effect when administered in combination with artesunate, excellent tolerability in mice (all mice survived after an oral treatment with a 1000 mg/kg dose), and oral efficacy at 50 mg/kg in a mouse model of P. berghei malaria (62% reduction in parasitemia on day 5 postinfection); thus, compound 50 was considered a lead compound for the discovery of new antimalarial agents.