Synthetic single and double aza-scorpiand macrocycles acting as inhibitors of the antioxidant enzymes iron superoxide dismutase and trypanothione reductase in Trypanosoma cruzi with promising results in a murine model

The anti-chagasic activity of a series of eleven derivatives of aza-scorpiand-like macrocycles, some of them newly synthesised, was assayed. The four compounds with the best selectivity indices in vitro were subjected to in vivo assays. Tests in a murine model of the acute phase of Chagas disease showed a two-fold reduction in parasitaemia compared to that with benznidazole. Furthermore, compounds 7 and 11, with 4-pyridine and phenanthroline substituents in the lateral chain, caused a remarkable decrease in parasitaemia reactivation during the chronic phase after inducing immunosuppression in mice. These activity studies were complemented by measuring their inhibitory effect towards the antioxidant parasite-specific enzymes, iron superoxide dismutase (Fe-SOD) and trypanothione reductase, the metabolites excreted after treatment and ultrastructural alterations. The ability of the selected macrocycles to complex with Fe(II) and Fe(III) was studied using potentiometric methods. Detailed molecular dynamics studies provided interesting pointers about the way in which the compounds approach and modify the active centre of Fe-SOD. The activity, low toxicity, stability, low cost of the starting materials and straightforward synthesis make these compounds appropriate molecules for the development of affordable anti-chagasic agents.