Use of scorpion tail-like macrocyclic compounds for preparing a pharmaceutical or veterinary composition for treating diseases caused by parasites, where the diseases are Chagas disease and leishmaniasis. Application Number: P201132035. Patent Assignee: UV/ UGR. Inventors: Garcia-Espana Monsonis E, Clares Garcia M P, Blasco Llopis S, Soriano Coto C, Gonzalez Garcia J, Verdejo Viu B, Inclan Nafria M, Sanchez Moreno M, Marin Sanchez C, Olmo Arevalo F, Soriano Soto C.