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Projeto de investigação
Utilization of host cell resources by the malaria parasite in the liver
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Chloroquine-containing organoruthenium complexes are fast-acting multistage antimalarial agents
Publication . Macedo, Taís S.; Colina-Vegas, Legna; da Paixão, Marcelo; Navarro, Maribel; Barreto, Breno C.; Oliveira, Poliana C. M.; Macabira, Simone G.; Machado, Marta; Prudêncio, Miguel; D'Alessandro, Sarah; Basilico, Nicoletta; Moreira, Diogo R. M.; Batista, Alzir A.; Soares, Milena B. P.
We report the pharmacological activity of organoruthenium complexes containing chloroquine (CQ) as a chelating ligand. The complexes displayed intraerythrocytic activity against CQ-sensitive 3D7 and CQ-resistant W2 strains of Plasmodium falciparum, with potency and selectivity indexes similar to those of CQ. Complexes displayed activity against all intraerythrocytic stages, but moderate activity against Plasmodium berghei liver stages. However, unlike CQ, organoruthenium complexes impaired gametocyte viability and exhibited fast parasiticidal activity against trophozoites for P. falciparum. This functional property results from the ability of complexes to quickly induce oxidative stress. The parasitaemia of P. berghei-infected mice was reduced by treatment with the complex. Our findings demonstrated that using chloroquine for the synthesis of organoruthenium complexes retains potency and selectivity while leading to an increase in the spectrum of action and parasite killing rate relative to CQ.
Reinvestigating old pharmacophores: are 4-Aminoquinolines and Tetraoxanes potential two-stage antimalarials?
Publication . Terzić, Natasa; Konstantinović, Jelena; Tot, Mikloš; Burojević, Jovana; Djurković-Djaković, Olgica; Srbljanović, Jelena; Štajner, Tijana; Verbić, Tatjana; Zlatović, Mario; Machado, Marta; Albuquerque, Inês S.; Prudêncio, Miguel; Sciotti, Richard J.; Pecic, Stevan; D’Alessandro, Sarah; Taramelli, Donatella; Šolaja, Bogdan A.
The syntheses and antiplasmodial activities of various substituted aminoquinolines coupled to an adamantane carrier are described. The compounds exhibited pronounced in vitro and in vivo activity against Plasmodium berghei in the Thompson test. Tethering a fluorine atom to the aminoquinoline C(3) position afforded fluoroaminoquinolines that act as intrahepatocytic parasite inhibitors, with compound 25 having an IC50 = 0.31 μM and reducing the liver load in mice by up to 92% at 80 mg/kg dose. Screening our peroxides as inhibitors of liver stage infection revealed that the tetraoxane pharmacophore itself is also an excellent liver stage P. berghei inhibitor (78: IC50 = 0.33 μM). Up to 91% reduction of the parasite liver load in mice was achieved at 100 mg/kg. Examination of tetraoxane 78 against the transgenic 3D7 strain expressing luciferase under a gametocyte-specific promoter revealed its activity against stage IV-V Plasmodium falciparum gametocytes (IC50 = 1.16 ± 0.37 μM). To the best of our knowledge, compounds 25 and 78 are the first examples of either an 4-aminoquinoline or a tetraoxane liver stage inhibitors.
Inhibition of Plasmodium liver infection by Ivermectin
Publication . Mendes, António M.; Albuquerque, Inês S.; Machado, Marta; Pissarra, Joana; Meireles, Patricia; Prudêncio, Miguel
Avermectins are powerful endectocides with an established potential to reduce the incidence of vector-borne diseases. Here, we show that several avermectins inhibit the hepatic stage of Plasmodium infection in vitro Notably, ivermectin potently inhibits liver infection in vivo by impairing parasite development inside hepatocytes. This impairment has a clear impact on the ensuing blood stage parasitemia, reducing disease severity and enhancing host survival. Ivermectin has been proposed as a tool to control malaria transmission because of its effects on the mosquito vector. Our study extends the effect of ivermectin to the early stages of mammalian host infection and supports the inclusion of this multipurpose drug in malaria control strategies.
Primaquine–pyrimidine hybrids: synthesis and dual-stage antiplasmodial activity
Publication . Kaur, Hardeep; Machado, Marta; de Kock, Carmen; Smith, Peter; Chibale, Kelly; Prudêncio, Miguel; Singh, Kamaljit
A series of novel pyrimidine-primaquine hybrids were synthesized and their effectiveness against the blood and liver stages of malaria parasites was evaluated. The hybrids displayed enhanced liver stage in vitro activity against P. berghei liver stage infection.
Enantiopure Indolizinoindolones with in vitro activity against blood- and liver-stage malaria parasites
Publication . Pereira, Nuno A. L.; Monteiro, Ângelo; Machado, Marta; Gut, Jiri; Molins, Elies; Perry, Maria Jesus; Dourado, Jorge; Moreira, Rui; Rosenthal, Philip J.; Prudêncio, Miguel; Santos, Maria M. M.
Malaria continues to be a major cause of morbidity and mortality to this day, and resistance to drugs like chloroquine has led to an urgent need to discover novel chemical entities aimed at new targets. Here, we report the discovery of a novel class of potential antimalarial compounds containing an indolizinoindolone scaffold. These novel enantiopure indolizinoindolones were synthesized, in good-to-excellent yields and excellent diastereoselectivities, by cyclocondensation reaction of (S)- or (R)-tryptophanol and 2-acyl benzoic acids, followed by intramolecular α-amidoalkylation. Interestingly, we were able to synthesize for the first time 7,13b-cis indolizinoindolones in a two-step route. The novel compounds showed promising activity against erythrocytic stages of the human malaria parasite, Plasmodium falciparum, and liver stages of the rodent parasite Plasmodium berghei. In particular, an (S)-tryptophanol-derived isoindolinone was identified as a promising starting scaffold to search for novel antimalarials, combining excellent activity against both stages of the parasite's life cycle with low cytotoxicity and excellent metabolic and chemical stability in vitro.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/SAU-MIC/117060/2010