Palladium(II) imine ligands cyclometallated complexes with a potential leishmanicidal activity on Leishmania (L.) amazonensis

Abstract

The leishmaniasis, considered a neglected disease, is caused by a protozoan from the genus Leishmania. There is an urgent need to search for safer, cheaper, and more effective treatments against leishmaniasis. In this context, transition metal complex activities have been studied, as palladium, which has become an interesting alternative as metal-based drugs. In this study, three new palladium(II) complexes, obtained from two imine ligands, were synthesized and characterized by elemental analyses, infrared and 1H NMR spectroscopies. The in vitro evaluation of ligands and complexes has been tested on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis and its cytotoxicity on murine macrophages. All complexes exhibited a leishmanicidal activity on promastigotes and amastigotes forms. The ligands activities were improved after coordination with palladium, and the replacement by some substituents has increased the leishmanicidal activity even more. Complexes with chloride and thiocyanate showed an improvement of activity when compared to their respective ligands, with better selectivity index (SI > 1) and less damage on mammalian cells when compared to a reference drug pentamidine. These compounds are promising agents for leishmaniasis treatment, and the results emphasize the potential properties of compounds with transition metal for medical applications.