ABSTRACT
As part of our continuous research for the discovery of bioactive compounds against Trypanosoma cruzi and Leishmania infantum, the alkaloid (6aS)-dicentrine (1) was oxidized to afford (6aS,6S)- (2) and (6aS,6R)- (3) dicentrine-N-oxides. Evaluation of the cytotoxicity against NCTC cells indicated that 2 and 3 are non-toxic (CC50 > 200 µM) whereas 1 demonstrated CC50 of 52.0 µM. Concerning T. cruzi activity against amastigotes, derivatives 2 and 3 exhibited EC50 values of 9.9 µM (SI > 20.7) and 27.5 µM (SI > 7.3), respectively, but 1 is inactive (EC50 > 100 µM). Otherwise, when tested against L. infantum amastigotes, 1 and 3 exhibited EC50 values of 10.3 µM (SI = 5.0) and 12.7 µM (SI > 15.7), respectively, being 2 inactive (EC50 > 100 µM). Comparing the effects of positive controls benznidazol (EC50 = 6.5 µM and SI > 30.7) and miltefosine (EC50 = 10.2 µM and SI = 15.0), it was observed a selective antiparasitic activity to diastereomers 2 and 3 against T. cruzi and L. infantum. Considering stereochemical aspects, it was suggested that the configuration of the new stereocenter formed after oxidation of 1 played an important role in the bioactivity against amastigotes of both tested parasites.
