Existing therapies for leishmaniasis face challenges including adverse reactions, reduced effectiveness, and emerging resistance. Plants from the Thymus genus are recognized for their therapeutic properties. This research investigated the potential antileishmanial activity and toxic effects of a hydroalcoholic extract derived from Thymus kotschyanus through laboratory-based tests. The above-ground portions of T. kotschyanus were processed via maceration using 70% ethanol to obtain the extract. Its impact was assessed on both promastigote and amastigote forms of Leishmania major by enumerating parasites directly within a macrophage system. Toxicity was measured using the MTT method. Rates of macrophage infection and counts of intracellular amastigotes were compared against untreated controls and glucantime-treated groups (standard drug). The extract suppressed proliferation of promastigotes and amastigotes, with peak inhibition at 48 hours. IC50 values against non-infected macrophages reached 381.8 μg/L at 48 hours and 392.9 μg/L at 72 hours. Doses of 300 and 350 μg/mL markedly lowered the proportion of infected macrophages (p=0.042 and p=0.001, respectively) and the quantity of amastigotes inside macrophages (p<0.05 and p=0.001, respectively) relative to controls. These doses outperformed 5 μg/mL glucantime in reducing amastigote counts across time points (p<0.05 and p<0.01, respectively), while showing comparable efficacy to 10 and 15 μg/mL glucantime. The hydroalcoholic extract from Thymus kotschyanus could serve as a promising and relatively non-toxic natural agent against L. major. Additional studies are required to establish it as a novel plant-based treatment.
