Computational Screening for the Identification of Potential Phytochemical Inhibitors of Leishmania infantum Trypanothione Reductase

Leishmaniasis is a vector-borne parasitic disease that possesses high morbidity and a variety of clinical manifestations. Of all the clinical manifestations, visceral leishmaniasis (VL) is the deadliest and its etiological organisms are mainly Leishmania infantum (L. infantum) and Leishmania donovani (L. donovani). In the tropical and subtropical regions, L. infantum is the main causative agent of VL, and it creates a favorable biological milieu in the host through the multifaceted action of its trypanothione reductase (TryR), which mediates the reduction of oxidized trypanothione to its reduced form, leading to the replenishment of the antioxidant capacity of the parasite and detoxifying the reactive oxygen and nitrogen species imposed by the host's immune system. The distinct structural and functional differences of this enzyme compared to its human homologs and its pivotal role in the survival of the parasite have rendered it an attractive target for drug discovery odysseys. Consequently, this study aims to identify potential inhibitors of TryR of L. infantum from Allium sativum (A. sativum) using molecular modeling techniques. The identified compounds were first screened using molecular docking, after which the pharmacokinetics properties of the top-scoring compounds were further evaluated. Further evaluation of the stability of the complexes of the lead compounds with TryR revealed their relative stability over 100 ns simulation period. Ultimately, the lead compounds namely beta-sitosterol, (E)-alpha-bisabolene, and agapanthagenin were found to possess suitable properties based on the results of this study and can serve as inhibitors of TryR of L. infantum upon further in vitro and in vivo study.