In Vitro Effect of Some Medicinal Plants on Leishmania major Strain MRHO/IR/75/ER

Leishmaniasis is a tropical disease caused by protozoan parasites from the genus Leishmania. In this study, we aimed at investigating the in vitro anti-leishmanial effect of essential oils of Rosmarinus officinalis, Mentha pulegium, Foeniculum vulgare, Lippia citriodora and Pelargonium graveolens.    

The essential oils were prepared from freshly dried and powdered plants with steam-distilled water. Iranian strain of Leishmania promastigotes was cultured in RPMI medium and the inhibitory effects of different concentrations (25, 32, 62.5, 125, 250, 500 and 1000 μg/ml) of the essential oils were investigated at 24, 48 and 72 hours. The number of live parasites before and after treatment with the essential oils was counted by trypan blue 10% staining and using neobar lam. 

The essential oils significantly decreased the number of promastigotes in a dose-dependent manner (P<0.05). However, the inhibitory effects of F. vulgare and R. officinalis essential oils were more profound compared to other essential oils. Moreover, concentrations of 500 and 1000 μg/ml of these two essential oils exerted equal and more anti-leishmanial potency compared to glucantime, the first-line drug used for treatment of leishmaniasis. 

Based on the results, it is recommended to evaluate the in vivo anti-leishmanial effects of the tested essential oils, particularly F. vulgare and R. officinalis.