Evaluation of the effect on the mitochondrial membrane potential in L. amazonensis caused by Calealactone C isolated from Calea pinnatifida

C. pinnatifida, popularly known as "aruca" and “cipó-cruz”, has been encountered specially in Brazilian “cerrado” biome, and has been used in folk medicine to treat stomachaches, giardiasis and amebiasis3. Calealactone C, a germacranolide not reported previously for this species, isolated from the fractionation of the leaves of the crude methanolic extract of C. pinnatifida, displayed activity against promastigote forms of L. amazonensis with EC50 of 4.6 g mL-1. The mitochondrial membrane potential was analyzed in promastigote forms using the probe rhodamine 123 (Rho). Oligomycin A was used as an inhibitor of mitochondrial membrane potential at 7,91 μg mL-1. The compound demonstrated the same pattern of fluorescence intensity reduction over oligomycin A, a substance that acts as an inhibitor of ATP synthase, preventing the formation of ATP. Thus, to the best of our knowledge, this is the first study showing that calealactone C targets parasite mitochondria, leading to possible cell death. According to the results, this organella can be the first one to be impacted with the treatment.