New uses for old complexes: The very first report on the trypanocidal activity of symmetric trinuclear ruthenium complexes

Abstract

This work reports on the trypanocidal activity of a series of symmetric triruthenium complexes combined with azanaphthalene ligands of general formula [Ru3O(CH3COO)6(L)3]PF6 (L=(1) quinazoline (qui), (2) 5-nitroisoquinoline (5-nitroiq), (3) 5-bromoisoquinoline (5-briq), (4) isoquinoline (iq), (5) 5-aminoisoquinoline (5-amiq), and (6) 5,6,7,8-tetrahydroisoquinoline (thiq)). All complexes within the series presented in vitro trypanocidal activity against both the trypomastigote and amastigote forms of T. cruzi. The IC50 values obtained for complexes 1–6 ranged from 1.39 to 165.9μM for the trypomastigote form and from 1.06 to 53.16μM for the amastigote form. These values were lower than the values observed for the metallic core [Ru3O(CH3COO)6(CH3OH)3]+ itself and for the free ligands in all cases. Remarkably, complex 6 displayed lower IC50 values than the reference drug (benznidazole) for the acute (trypomastigote form) and chronic (amastigote form) phases of Chagas disease. These findings, combined with the low toxicity against healthy cells (LLK-MK2 strain) and a high SI value (Selectivity Index >10) make complex 6 an excellent candidate for in vivo tests.