Anti-leishmanial Activity of Methanolic Extract of Nerium oleander L. against Leishmania major

ABSTRACT             Background and Objectives: Leishmaniasis is a public health problem caused by the protozoan Leishmania. Pentavalent antimonials are currently used for treatment of leishmaniasis, but they have serious side effects. Nerium oleander L. has been used in traditional medicine due to its various health-protective properties. This study aimed to investigate anti-leishmanial activity of N. oleander L. leaves extract against Leishmania major promastigotes and amastigotes in vitro.             Methods: L. major promastigotes were cultured in RPMI 1640 medium supplied with 10% fetal bovine serum. Different concentrations were prepared from the extract and added to L. major promastigotes seeded in 96-well plates. Viability percentage was evaluated by direct counting and MTT assay after 24, 48 and 72 hours. To investigate the cytotoxic effect of N. oleander L. on L. major amastigotes, the plant extract was added to amastigotes cultured in intraperitoneal macrophages. The mean number of amastigotes was calculated by direct counting after 24 and 48 hours.              Results: All concentrations of the extract significantly reduced the viability of promastigotes when compared with the controls. Half-maximal inhibitory concentration was estimated to be 22.21 µg/ml after 24 hours. Percentage of cytotoxicity in amastigotes exposed to 20 μg/ml of the extract was 53.61% and 53.27% after 24 and 48 hours, respectively. In addition, percentage of cytotoxicity in amastigotes exposed to 80 μg/ml of the N. oleander L. extract was 53.77% and 55.48% after 24 and 48 hours, respectively.             Conclusion: The N. oleander L. extract exerts anti-leishmanial activity on L. major promastigotes in a time- and dose-dependent manner.              Keywords: Leishmania major, Nerium.