Background: We designed hybrid molecules between propamidine and benzimidazole in
order to retain the antiprotozoal action, but decreasing the toxic effect of the molecule.
Objective: Design and prepare 12 hybrids for testing their antiparasitic effect over three protozoa:
Giardia intestinalis, Trichomonas vaginalis and Leishmania mexicana, as well as conduct several in
silico simulations such as toxicological profile, molecular docking and molecular dynamics in order
to understand their potential mode of action.
Methods: Hybrids 1-3, 6-9 and 12 were obtained using a chemical pathway previously reported.
Compounds 4, 5, 10 and 11 were prepared using a one-pot reduction–cyclization reaction. The in vitro
antiparasitic and cytotoxic activities of these compounds were conducted. It was calculated several
properties such as toxicity, PK behavior, as well as docking studies and molecular dynamics of
the most active compound performed in a DNA sequence dodecamer in comparison with propamidine.
Results: Compound 2 was 183, 127 and 202 times more active against G. intestinalis than metronidazole,
pentamidine and propamidine. It was eleven times more active than pentamidine against L.
mexicana. This compound showed low in vitro mammalian cytotoxicity. Molecular simulations
showed a stable complex 2-DNA that occurred in the minor groove, analogous to propamidine-DNA
Conclusion: Compound 2, exhibited the higher bioactivity, especially towards G. intestinalis and L.
mexicana. This study demonstrated that the replacement of benzimidazole scaffold instead of toxic
amidine group in propamidine, results in an enhancement of antiprotozoal bioactivity. The preliminary
molecular dynamics simulation suggests that the ligand–DNA complex is stable.