In vitro and in vivo Anti-leishmanial Potential of [Ag (PTA)4]BF4 and [Ag(HBPz3)(PPh3)] Silver Complexes

Background: American tegumentary leishmaniasis is a parasitic disease known for being difficult to treat; therefore, the search for more effective therapeutic methods is necessary. The objective of this study was to evaluate the in vitro and in vivo antileishmanial activity of silver complexes [Ag(PTA)4]BF4 (Ag1) and [Ag(HBPz3)(PPh3)] (Ag2) against Leishmania (Leishmania) amazonensis [L. (L.) amazonensis] and Leishmania (Viannia) guyanensis. Methods: In vitro bioassays were performed to evaluate the activity of the complexes against promastigote and amastigote forms and evaluate their cytotoxicity. In vivo experiments were performed with hamsters (Mesocricetus auratus) infected and treated topically with two gels containing each metallic complex. Results: Both complexes reduced the number of viable parasites against the promastigote forms of L. (L.) amazonensis. Ag2 was mainly effective against the amastigote forms. The Ag2 complex did not present cellular cytotoxicity, and regarding the selectivity index, both complexes were considered acceptable, with Ag2 having the best selectivity index in murine peritoneal macrophages in relation to L. (L.) amazonensis. Ag2 showed better results in the topical treatment against infections caused by L. (L.) amazonensis, with a small reduction in the lesion volume after the 14th day of treatment and less parasitic load at the lesion site. Conclusions: Ag2 was more effective than Ag1 against L. (L.) amazonensis.