Leishmanicidal Activity and Cytotoxicity of Thymus kotschyanus Hydroalcoholic Extract: an In Vitro Assessment

Background and objectives: Current leishmaniasis treatment shows limitations such as side effects, low efficacy, and resistance. Thymus species are well-known as medicinal plants. This study evaluated antileishmanial efficacy and cytotoxicity of Thymus kotschyanus hydroalcoholic extract in in vitro experiments. Methods: Aerial parts of T. kotschyanus were extracted by maceration method with 70% ethanol. The hydroalcoholic extract was evaluated against Leishmania major promastigote and amastigote stages by directly counting the number of parasites in a macrophage model. Cytotoxicity of the extract was evaluated by MTT assay. The infectivity rate and amastigote numbers in macrophages were determined compared to control and glucantime (as a reference drug) groups. Results: The crude extract inhibited the growth of promastigotes and amastigotes with the highest effect observed at 48 h. The IC50 values of T. kotschyanus on uninfected macrophages were 381.8 and 392.9 μg/mL at 48 and 72 hours, respectively. The extract of 300 and 350 μg/mL showed a significant reduction in the percentage of infected macrophages (p=0.042, p=0.001, respectively) and intra-macrophage amastigote numbers (p<0.05 and p=0.001, respectively) compared to control groups. The concentrations of 300 and 350 µg/mL were significantly more effective on the mean number of amastigote forms than 5 µg/mL glucantime for each point time (p<0.05, p<0.01, respectively); whereas these values had equal effects with 10 and 15 μg/mL glucantime. Conclusion: Thymus kotschyanus extract might be considered an effective and safe herbal material against L. major. Nevertheless, supplementary investigations will be necessary to recognize the plant as a new herbal therapy.