Chagas’ disease is a neglected tropical disease caused by Trypanosoma cruzi and constitutes a serious public health problem for Latin America. Its unsatisfactory chemotherapy stimulates the search for novel antiparasitic compounds. Amidines and related compounds exhibit well-known activity towards different microbes including T. cruzi. In this vein, our present aim was to evaluate the biological effect of 10 novel structurally related amidines in vitro against bloodstream and intracellular forms of the parasite as well as their potential toxicity on cardiac cell cultures. Our results show that although active against the extracellular forms, with some of them like DB2247 being 6-fold more effective than benznidazole and displaying very low toxicity (>96 μ m), none presented superior trypanocidal effect against intracellular forms as compared with the reference drug. These results may be due to differences in susceptibility profiles related to distinct uptake/extrusion mechanisms and cellular targets between bloodstream and amastigote forms. The present study adds to the knowledge base for the future design of novel amidines that may provide promising activity against T. cruzi.

No vaccines or safe chemotherapy are available for Chagas disease. Pentamidine and related di-cations are DNA minor groove-binders with broad-spectrum anti-protozoal activity. Therefore our aim was to evaluate the in vitro efficacy of di-cationic compounds – DB1645, DB1582, DB1651, DB1646, DB1670 and DB1627 – against bloodstream trypomastigotes (BT) and intracellular forms of Trypanosoma cruzi. Cellular targets of these compounds in treated parasites were also analysed by fluorescence and transmission electron microscopy (TEM). DB1645, DB1582 and DB1651 were the most active against BT showing IC50 values ranging between 0·15 and 6·9 μm. All compounds displayed low toxicity towards mammalian cells and DB1645, DB1582 and DB1651 were also the most effective against intracellular parasites, with IC50 values ranging between 7·3 and 13·3 μm. All compounds localized in parasite nuclei and kDNA (with greater intensity in the latter structure), and DB1582 and DB1651 also concentrated in non-DNA-containing cytoplasmic organelles possibly acidocalcisomes. TEM revealed alterations in mitochondria and kinetoplasts, as well as important disorganization of microtubules. Our data provide further information regarding the activity of this class of compounds upon T. cruzi which should aid future design and synthesis of agents that could be used for Chagas disease therapy.

Two aromatic diamidines, furamidine (DB75) and its phenyl-substituted analogue (DB569), which exhibit trypanocidal activity, were assayed against Trypanosoma cruzi and were found to induce apoptosis-like death characteristics such as nuclear DNA condensation and fragmentation, decreased mitochondrial membrane potential and phosphatidylserine exposure. DB569 displays superior trypanocidal activity compared to furamidine and also had higher ability to induce apoptosis-like death in treated parasites. The present results showing apoptosis-like death in T. cruzi after treatment with both DB75 and DB569 make important contributions to the understanding of the mechanisms of the aromatic diamidines, which represent promising trypanocidal compounds.