1. Investigación

Leishmaniasis a ects around 12 million people worldwide and is estimated to cause the ninth-largest disease burden. There are three main forms of the disease, visceral (VL), cutaneous (CL), and mucocutaneous (MCL), leading to more than one million new cases every year and several thousand deaths. Current treatments based on chemically synthesized molecules are far from ideal. In this study, we have tested the in vitro and in vivo e cacy of ursolic acid (UA), a multifunctional triterpenoid with well-known antitumoral, antioxidant, and antimicrobial e ects on di erent Leishmania strains. The in vitro antileishmanial activity against the intracellular forms was six and three-fold higher compared to extracellular forms of L. amazonensis and L. infantum, respectively. UA also showed to be a potent antileishmanial drug against both VL and CL manifestations of the disease in experimental models. UA parenterally administered at 5 mg/kg for seven days significantly reduced the parasite burden in liver and spleen not only in murine acute infection but also in a chronic-infection model against L. infantum. In addition, UA ointment (0.2%) topically administered for four weeks diminished (50%) lesion size progression in a chronic infection model of CL caused by L. amazonensis, which was much greater than the e ect of UA formulated as an O/W emulsion. UA played a key role in the immunological response modulating the Th1 response. The exposure of Leishmania-infected macrophages to UA led to a significant di erent production in the cytokine levels depending on the Leishmania strain causing the infection. In conclusion, UA can be a promising therapy against both CL and VL.

The current therapies of leishmaniasis, the second most widespread neglected tropical disease, have limited e ectiveness and toxic side e ects. In this regard, natural products play an important role in overcoming the current need for new leishmanicidal agents. The present study reports a bioassay-guided fractionation of the ethanolic extract of leaves of Piper pseudoarboreum against four species of Leishmania spp. promastigote forms, which a orded six known alkamides (1–6). Their structures were established on the basis of spectroscopic and spectrometric analysis. Compounds 2 and 3 were identified as the most promising ones, displaying higher potency against Leishmania spp. promastigotes (IC50 values ranging from 1.6 to 3.8 M) and amastigotes of L. amazonensis (IC50 values ranging from 8.2 to 9.1 M) than the reference drug, miltefosine. The e cacy of (E)-piplartine (3) against L. amazonensis infection in an in vivo model for cutaneous leishmaniasis was evidenced by a significant reduction of the lesion size footpad and spleen parasite burden, similar to those of glucantime used as the reference drug. This study reinforces the therapeutic potential of (E)-piplartine as a promising lead compound against neglected infectious diseases caused by Leishmania parasites.