In vitro and in vivo evaluation of dialkylphosphorylhydrazones against Leishmania chagasi promastigotes and amastigotes

In our previous study, two new dialkylphosphorylhydrazones (DAPHs) have been designed targeting antileishmanial activity against Leishmania braziliensis and Leishmania amazonensis parasites, and their mechanism of action, as well as their leishmanicidal activity against Leishmania chagasi, was evaluated. The present work aimed to evaluate the in vitro and in vivo activities of DAPHs against L. chagasi, in addition to proposing a mechanism of action based on ultrastructural alterations and in silico studies. Then, the in vitro activity of DAPHs against promastigotes and amastigotes from L. chagasi, as well as in vivo results in a golden Syrian hamster (Mesocricetus auratus) animal model, was determined in this study. A mechanism of action was proposed considering observations verified by scanning electron microscopy (SEM) and molecular docking simulations using the GOLD (R) software. DAPHs 4m and 4n were not cytotoxic on macrophages at the concentrations tested, among which analog 4n exhibited a maximum effect of 84.3% against L. chagasi amastigotes, which is greater than that for miltefosine (66.2%). Further analyses demonstrated that it causes morphological changes in promastigote forms compatible with induced apoptosis. In addition, no significant in vivo alterations were observed for both DAPH compounds. Still, our molecular modeling protocol was able to predict a tridimensional structure for hexokinase protein from L. infantum chagasi (LicHK), in which subsequent docking studies demonstrated that 4m and 4n are capable of interacting with this target in a more efficient binding mode than its endogenous ligand, G6P. The novel DAPHs 4m and 4n could serve as potent hit compounds for designing new leishmanicidal agents.