A new synthetic antimalarial drug, a salt derived from two antimalarial molecules, mefloquine (MQ) and artesunate (AS), here named MEFAS, has been tested for its pharmacological activity. Combinations of AS plus MQ hydrochloride are currently being used in areas with drug-resistant Plasmodium falciparum parasites; although AS clears parasitemia in shorter time periods than any other antimalarial drug, it does not cure infected patients; in addition, MQ causes side effects and is rather expensive, important problems considering that malaria affects mostly populations in poor countries. Here, we show that MEFAS is more effective than the combination of AS and MQ, tested in parallel at different mass proportions, against P. falciparum (chloroquine-resistant clone W2 and chloroquine-sensitive clone 3D7) in vitro and in mice infected with Plasmodium berghei, promoting cure of this infection. MEFAS tested against HepG2 hepatoma cells exhibited lower toxicity than the antimalarials AS and MQ alone or combined. Possible targets of MEFAS have been studied by confocal microscopy using fluorescent probes (Fluo-4 AM and BCECF-AM) in P. falciparum synchronous culture of W2-infected red blood cells. Dynamic images show that MEFAS exhibited intracellular action increasing cytoplasmic Ca 2؉ at 1.0 ng/ml. This effect was also observed in the presence of tapsigargin, an inhibitor of SERCA, suggesting an intracellular target distinct from the endoplasmic reticulum. Trophozoites loaded with BCECF-AM, when treated with MEFAS, were still able to mobilize protons from the digestive vacuole (DV), altering the pH gradient. However, in the presence of bafilomycin A1, an inhibitor of the H ؉ pump from acidic compartments of eukaryotic cells, MEFAS had no action on the DV. In conclusion, the endoplasmic reticulum and DV are intracellular targets for MEFAS in Plasmodium sp., suggesting two modes of action of this new salt. Our data support MEFAS as a candidate for treating human malaria.

The fungus Lentinus strigosus (Pegler 1983) (Polyporaceae, basidiomycete) was selected in a screen for inhibitory activity on Trypanosoma cruzi trypanothione reductase (TR). The crude extract of L. strigosus was able to completely inhibit TR at 20 µg/ml. Two triquinane sesquiterpenoids (dihydrohypnophilin and hypnophilin), in addition to two panepoxydol derivatives (neopanepoxydol and panepoxydone), were isolated using a bioassay-guided fractionation protocol. Hypnophilin and panepoxydone displayed IC 50 values of 0.8 and 38.9 µM in the TR assay, respectively, while the other two compounds were inactive. The activity of hypnophilin was confirmed in a secondary assay with the intracellular amastigote forms of T. cruzi, in which it presented an IC 50 value of 2.5 µM. Quantitative flow cytometry experiments demonstrated that hypnophilin at 4 µM also reduced the proliferation of human peripheral blood monocluear cells (PBMC) stimulated with phytohemaglutinin, without any apparent interference on the viability of lymphocytes and monocytes. As the host immune response plays a pivotal role in the adverse events triggered by antigen release during treatment with trypanocidal drugs, the ability of hypnophilin to kill the intracellular forms of T. cruzi while modulating human PBMC proliferation suggests that this terpenoid may be a promising prototype for the development of new chemotherapeutical agents for Chagas disease. Key words: fungal natural products -Chagas disease -drug discovery -immunomodulators -BasidiomycotaChagas disease is caused by the protozoan parasite Trypanosoma cruzi and affects millions of people in Latin America, having an enormous economic and social impact in the endemic areas. These patients rely on treatment with nitrofuran (nifurtimox; Bayer) or nitroimidazol (benznidazole; Roche), medicines that display little or no activity in chronic infections, in spite of their beneficial effect during the acute phase of the disease (Cançado 2002, Coura & Castro 2002. However, significant differences in the therapeutic effectiveness are observed between these two drugs, especially when considering distinct geographical areas, which is probably due to the occurrence of naturally resistant and susceptible T. cruzi strains (Filardi & Brener 1987, Toledo et al. 2003. Furthermore, both drugs cause several side effects that contribute to their reduced use in clinical medicine (Cançado 1985). Thus, new compounds are needed to develop more effective medicines to treat Chagas disease, espe- cially in its chronic phase, is needed (Schmidt & KrauthSiegel 2002, Nwaka & Ridley 2003. However, due to low profit prospects, the development of new trypanocidal drugs is not attractive to the pharmaceutical industry (Nwaka & Ridley 2003). Thus, this endeavor is being conducted mainly in academic laboratories (Fairlamb 1999).Among the many different strategies for drug discovery, screening the local biodiversity for bioactive natural products using appropriate bioassays is an interesting alternative for researchers in affec...