In vitro activities of thiadiazine derivatives against Leishmania amazonensis.

Ten thiadiazine derivatives were tested in vitro for antiparasitic effects against both extracellular promastigotes and intracellular amastigotes of Leishmania amazonensis. The results showed that the evaluated compounds exhibited a strong antiproliferative activity on all developmental stages of the parasite. The minimal inhibitory concentration and the 50 % effective concentration values against the promastigote were 2.1-5.1 microg/ml and 0.6-1.8 microg/ml, respectively. The tested compounds caused an irreversible inhibition of the promastigote growth either after 1 h of treatment with 10 microg/ml or after 24 h with 1 microg/ml. Also, the thiadiazine derivatives were active against amastigotes producing between 12 and 89 % of reduction of infection at 100 ng/ml. However, the compounds exhibited high toxicity and provoked inhibition of the phagocytosis in the murine host cell.