Antileishmanial activity of Peganum harmala extract on the in vitro growth of Leishmania major promastigotes in comparison to a trivalent antimony drug

Parasites of the genus Leishmania are transmitted by sandflies that ingest the parasite in the amastigote stage resident within macrophages, then inoculate the promastigote stage into other hosts. Peganum harmala, or Syrian Rue, has pharmacologically active compounds including several alkaloids with antiprotozoal properties, which are found especially in the seeds and the roots. In this research, Leishmania major were cultured in vitro, then by using a MTT assay, the biological activity of P. harmala extract in comparison to potassium antimonyl tartrate [Sb(III)] on L. major promastigotes was assessed. P. harmala extract and Sb(III) solutions for biological testing were prepared in PBS at 5000-20000 μg/mL and 62.5-500 μg/mL, respectively. All experiments were repeated at least three times in duplicate. For P. harmala extract and Sb(III), the concentration-response curve was plotted, from which IC50 values were determined. Both P. harmala extract and Sb(III) inhibited the growth of promastigote forms of L. major in vitro after 72 h. of incubation and had an IC50 of 1832.65 ± 89.72 μg/ mL and 17.87 ± 2.05 μg/mL, respectively. Statistical analysis of the results (optical density and inhibitory percentage) of the different concentrations of P. harmala extract and Sb(III) showed that there was no significant difference between P. harmala extract and Sb(III) (P>0.05) but with a concentration increase of P. harmala extract or Sb(III), optical density decreased significantly, while inhibitory percentage increased. The different concentrations resulted in different optical densities or inhibitory percentages (P<0.05) so that P. harmala extract is effective against L. major in vitro. key words: antileishmanial activity, Leishmania major, Peganum harmala, potassium antimonyl tartrate, MTT assay