The Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH) has been considered as a potential molecular target for antimalarials due to this parasite's dependence on glycolysis for energy production. Because the LDH enzymes found in P. vivax, P. malariae and P. ovale (pLDH) all exhibit ∼90% identity to PfLDH, it would be desirable to have new anti-pLDH drugs, particularly ones that are effective against P. falciparum, the most virulent species of human malaria. Our present work used docking studies to select potential inhibitors of pLDH, which were then tested for antimalarial activity against P. falciparum in vitro and P. berghei malaria in mice. A virtual screening in DrugBank for analogs of NADH (an essential cofactor to pLDH) and computational studies were undertaken, and the potential binding of the selected compounds to the PfLDH active site was analyzed using Molegro Virtual Docker software. Fifty compounds were selected based on their similarity to NADH. The compounds with the best binding energies (itraconazole, atorvastatin and posaconazole) were tested against P. falciparum chloroquine-resistant blood parasites. All three compounds proved to be active in two immunoenzymatic assays performed in parallel using monoclonals specific to PfLDH or a histidine rich protein (HRP2). The IC₅₀ values for each drug in both tests were similar, were lowest for posaconazole (<5 µM) and were 40- and 100-fold less active than chloroquine. The compounds reduced P. berghei parasitemia in treated mice, in comparison to untreated controls; itraconazole was the least active compound. The results of these activity trials confirmed that molecular docking studies are an important strategy for discovering new antimalarial drugs. This approach is more practical and less expensive than discovering novel compounds that require studies on human toxicology, since these compounds are already commercially available and thus approved for human use.

Mycobacterium tuberculosis (Mt) is a leading cause of infectious disease in the world today. This outlook is aggravated by a growing number of Mt infections in individuals who are immunocompromised as a result of HIV infections. Thus, new and more potent anti-tuberculosis agents are necessary. Therefore, DNA gyrase was selected as a target enzyme to combat Mt. In this work, the first three-dimensional molecular model of the hypothetical structures for the Mycobacterium tuberculosis DNA gyrase (mtDNAg) was elucidated by a homology modeling method. In addition, the orientations and binding affinities of some gatifloxacin analogs with those new structures were investigated. Our findings could be helpful for the design of new more potent gatifloxacin analogs.

Anthrax is a disease caused by Bacillus anthracis, a dangerous biological warfare agent already used for both military and terrorist purposes. An important selective target for chemotherapy against this disease is nucleoside hydrolase (NH), an enzyme still not found in mammals. Having this in mind we have performed molecular docking studies, aiming to analyze the three-dimensional positioning of six known inhibitors of Trypanosoma vivax NH (TvNH) in the active site of B. anthracis NH (BaNH). We also analyzed the main interactions of these compounds with the active site residues of BaNH and the relevant factors to biological activity. These results, together with further molecular dynamics (MD) simulations, pointed out to the most promising compounds as lead for the design of potential inhibitors of BaNH. Most of the docking and MD results obtained corroborated to each other. Additionally, the docking results also suggested a good correlation with experimental data.

Considering the risk represented by plague today as a potential biological warfare agent, we propose cytosolic Yersinia pestis dihydrofolate reductase (Y_p DHFR) as a new target to the design of selective plague chemotherapy. This enzyme has a low homology with the human enzyme and its crystallographic structure has been recently deposited in the Protein Data Bank (PDB). Comparisons of the docking energies and molecular dynamic behaviors of five known DHFR inhibitors inside a 3D model of Y_p DHFR (adapted from the crystallographic structure) and human DHFR (H_ss DHFR), revealed new potential interactions and suggested insights into the design of more potent H_ss DHFR inhibitors as well as selective inhibitors for Y_p DHFR.