Antiparasitic activities of novel ruthenium/lapachol complexes

• Five new ruthenium-lapachol complexes were synthesized and characterized.
• The complexes were evaluated against Leishmania amazonensis and Plamodium falciparum.
• The complexes are promising antiparasite metallodrug candidates.

The present study describes the synthesis, characterization, antileishmanial and antiplasmodial activities of novel diimine/(2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), 4,4′-methylbipyridine (Me-bipy) and 4,4′-methoxybipyridine (MeO-bipy)/phosphine/ruthenium(II) complexes containing lapachol (Lap, 2-hydroxy-3-(3-33 methyl-2-buthenyl)-1,4-naphthoquinone) as bidentate ligand. The [Ru(Lap)(PPh3)2(bipy)]PF6 (1), [Ru(Lap)(PPh3)2(Me-bipy)]PF6 (2), [Ru(Lap)(PPh3)2(MeO-bipy)]PF6(3) and[Ru(Lap)(PPh3)2(phen)]PF6 (4) complexes, PPh3 = triphenylphospine, were synthesized from the reactions of cis-[RuCl2(PPh3)2(X-bipy)] or cis-[RuCl2(PPh3)2(phen)], with lapachol. The [RuCl2(Lap)(dppb)] (5) [dppb = 1,4-bis(diphenylphosphine)butane] was synthesized from the mer-[RuCl3(dppb)(H2O)] complex. The complexes were characterized by elemental analysis, molar conductivity, infrared and UV–vis spectroscopy, 31P{1H} and 1H NMR, and cyclic voltammetry. The Ru(III) complex, [RuCl2(Lap)(dppb)], was also characterized by the EPR technique. The structure of the complexes [Ru(Lap)(PPh3)2(bipy)]PF6 and [RuCl2(Lap)(dppb)] was elucidated by X-ray diffraction. The evaluation of the antiparasitic activities of the complexes against Leishmania amazonensis and Plasmodium falciparum demonstrated that lapachol–ruthenium complexes are more potent than the free lapachol. The [RuCl2(Lap)(dppb)] complex is the most potent and selective antiparasitic compound among the five new ruthenium complexes studied in this work, exhibiting an activity comparable to the reference drugs.

Five ruthenium–lapachol complexes were synthesized and evaluated against Leishmania amazonensis and Plasmodium falciparum. The metal complexes are promising antiparasite metallodrug candidates, in which they are more potent than lapachol free and the reference drugs.Figure optionsDownload as PowerPoint slide