Development of 3D-QSAR and pharmacophoric models to design new anti-Trypanosoma cruzi agents based on 2-aryloxynaphthoquinone scaffold.

In this work we have collected a set of 30 trypanosomicidal naphthoquinones and developed pharmacophoric and 3D-QSAR models as tools for the design of new potential anti-Chagasic compounds. Firstly, qualitative information was obtained from SAR and pharmacophoric models identifying some fragments around the 2-aryloxynaphthoquinone scaffold important for the antiparasitic activity. Then, 3D-QSAR CoMFA and CoMSIA models were developed. The models showed adequate statistical parameters where the steric, electrostatic, and hydrophobic features explain the trypanosomicidal effect. Therefore, to validate our models, we carried out the design, synthesis, and biological evaluation on T. cruzi epimastigotes of five new compounds (33a-e). According to CoMFA model, three out of five compounds showed pIC50 values within one logarithmic unit of deviation. The two compounds that did not fit the predictions were those with high lipophilicity, which agreed with the SAR and pharmacophore models. Docking and molecular dynamic studies were performed on T. cruzi trypanothione reductase, in a proposed binding site for this type of naphthoquinone. Interestingly, 33a-e showed the same interaction pattern as a naphthoquinone inhibitor (2). Finally, predicted drug-likeness properties indicated that 33a-e have optimal oral bioavailability. Thus, this study provides new in silico models for obtaining novel trypanosomicidal compounds.

Key proteins in the polyamine-trypanothione pathway as drug targets against Trypanosoma cruzi.

In trypanosomatids, redox homeostasis is centered on trypanothione (N(1),N(8)-bis(glutathionyl)spermidine, T(SH)2), a low molecular weight thiol that is distinctive for this taxonomic family and not present in the mammalian host. Thus, the study of the metabolism of T(SH)2 is interesting as a potential therapeutic target. In this review, we summarize the existing evidence about the metabolism of thiols in Trypanosoma cruzi, focused on those proteins that can be considered the best candidates for selective therapy. Herein, we examine the biosynthetic pathway of T(SH)2, identifying three key points that are susceptible to attack pharmacologically: the activity of the trypanothione reductase (TR), the function of glutamate-cysteine ligase (GCL) and polyamine transport in T. cruzi. TR has been widely studied and is a good example for the development of the medicinal chemistry of antichagasic compounds. Conversely, GCL and the polyamine uptake system are high flow points in the reductive metabolism of the parasite. However, very little is known at the molecular level about these two systems. Therefore, their potential as targets for drug development is discussed, and it is suggested that research should focus on the production of alternative drugs for Chagas' disease treatment.