Antileishmanial Activities of Methanol Extract and Solvent Fraction of Clematis simensis Fresen Roots

Leishmaniasis is a neglected tropical disease affecting 12 million people and risks the lives of 350 million people globally. However, it has limited therapeutic options. Clematis simensis Fresen roots are used for the treatment of leishmaniasis in Ethiopian traditional medicine.

The aim of this study was to evaluate C. simensis Fresen roots' antileishmanial activities and cytotoxic effects.

In vitro antileishmanial activity of crude extract of C. simensis root and its solvent fractions was evaluated against axenic amastigotes and promastigotes of Leishmania aethiopica and Leishmania donovani. Their cytotoxicity against macrophage cells and red blood cells (RBCs) was evaluated. Median cytotoxic concentration (CC₅₀) and median inhibitory concentration (IC₅₀) were calculated using computer software GraphPad Prism 9.5.0. Data were expressed as mean ± standard error of the mean.

The crude extract and its hexane, chloroform, and aqueous fractions exhibited antileishmanial activities, with IC₅₀ values ranging from 4.43 ± 0.69 to 24.94 ± 4.12 μg/mL against promastigotes and 4.52 ± 1.25 to 34.97 ± 1.77 μg/mL against axenic amastigotes of Leishmania parasites. The cytotoxic effects (CC₅₀) of the extracts were 63.62 ± 4.06 ≤ CC50 ≤ 246.05 ± 32.84 μg/mL against macrophages, but > 1200 μg/mL against RBC. A selectivity index value greater than 1 indicates selective toxicity against Leishmania parasites, whereas a value less than 1 suggests selective toxicity against mammalian cells. In this study, the selectivity indices for the plant extracts ranged from 3.26 to 54.44.

The roots of the plant showed a promising antileishmanial activity that may provide a scientific justification for its use in traditional medicine. Further isolation, identification of active compounds, and establishment of the mechanism of action are warranted.