Towards development of new antimalarial compounds through in silico and in vitro assays.

Malaria is one of most widespread infectious disease in world. The antimalarial therapy presents a series of limitations, such as toxicity and the emergence of resistance, which makes the search for new drugs urgent. Thus, it becomes necessary to explore essential and exclusive therapeutic targets of the parasite to achieve selective inhibition. Enoyl-ACP reductase is an enzyme of the type II fatty acid biosynthetic pathway and is responsible for the rate-limiting step in the fatty acid elongation cycle. In this work, we use hierarchical virtual screening and drug repositioning strategies to prioritize compounds for phenotypic assays and molecular dynamics studies. The molecules were tested against chloroquine-resistant W2 strain of Plasmodium falciparum (EC50 between 330.05 and 13.92 µM). Nitrofurantoin was the best antimalarial activity at low micromolar range (EC50 = 13.92 µM). However, a hit compound against malaria must have a biological activity value below 1 µM. A large number of molecules present problems with permeability in biological membranes and reaching an effective concentration in their target's microenvironment. Nitrofurantoin derivatives with inclusions of groups which confer increased lipid solubility (methyl groups, halogens and substituted and unsubstituted aromatic rings) have been proposed. These derivatives were pulled through the lipid bilayer in molecular dynamics simulations. Molecules 14, 18 and 21 presented lower free energy values than nitrofurantoin when crossing the lipid bilayer.

Antileishmanial activity evaluation of thiazolidine-2,4-dione against Leishmania infantum and Leishmania braziliensis.

Leishmaniasis is responsible for approximately 65,000 annual deaths. Despite the mortality data, drugs available for the treatment of patients are insufficient and have moderate therapeutic efficacy in addition to serious adverse effects, which makes the development of new drugs urgent. To achieve this goal, the integration of kinetic and DSF assays against parasitic validated targets, along with phenotypic assays, can help the identification and optimization of bioactive compounds. Pteridine reductase 1 (PTR1), a validated target in Leishmania sp., is responsible for the reduction of folate and biopterin to tetrahydrofolate and tetrahydrobiopterin, respectively, both of which are essential for cell growth. In addition to the in vitro evaluation of 16 thiazolidine-2,4-dione derivatives against Leishmania major PTR1 (LmPTR1), using the differential scanning fluorimetry (ThermoFluor®), phenotypic assays were employed to evaluate the compound effect over Leishmania braziliensis (MHOM/BR/75/M2903) and Leishmania infantum (MHOM/BR/74/PP75) promastigotes viability. The ThermoFluor® results show that thiazolidine-2,4-dione derivatives have micromolar affinity to the target and equivalent activity on Leishmania cells. 2b is the most potent compound against L. infantum (EC50 = 23.45 ± 4.54 µM), whereas 2a is the most potent against L. braziliensis (EC50 = 44.16 ± 5.77 µM). This result suggests that lipophilic substituents on either-meta and/or-para positions of the benzylidene ring increase the potency against L. infantum. On the other hand, compound 2c (CE50 = 49.22 ± 7.71 µM) presented the highest selectivity index.