Effect of Schinus molle L. essential oil on Leishmania amazonensis: targeting proliferation, mitochondrial potential...

Schinus genus plants have a long history of use in traditional medicine, particularly in South America. The ethnopharmacological applications of Schinus species include antiseptic, antiplasmodial, antimalarial and antileishmanial properties.

In the present work, we investigated the action of essential oil (EO) against cutaneous leishmaniasis causing agent Leishmania amazonensis in promastigote and amastigote forms as well as cytotoxicity against host cells.

After hydrodistillation, drying and concentration of S. molle leaves, obtained EO chemical analysis was performed by gas chromatography-mass spectrometry. L. amazonensis promastigotes were treated or not (control) with different concentrations of the EO, being daily counted on Neubauer chamber up to 96 h after treatment. The effect of the EO on parasite promastigote forms was also analyzed by ultrastructural and mitochondrial membrane potential (ΔΨm) alterations. The cytotoxicity of S. molle essential EO on Balb/c mice peritoneal macrophages was evaluated by XTT cell viability assay. The anti-amastigote effect was quantified either by counting the fixed and Giemsa-stained intracellular parasites inside macrophages treated or not (control) with different concentrations of the EO or by amastigote-promastigote conversion rate. For the latter, infected macrophages were treated with SDS at 0.01 % and released amastigotes were grown at conditions that favored their transformation into promastigotes and those were then collected from the Schneider's Insect medium supernatant and counted.

S. molle EO had 33 identified compounds with sabinene (26.2 %) and epi-α-cadinol (15.2 %) as the major constituents. The EO significantly inhibited L amazonensis promastigotes growth even in very low concentrations with IC₅₀/96 h of 0.0196 ± 0.0036 μg/mL. The volatile oil induced autophagosome formation and cell shrinkage in promastigotes and disruption of parasite mitochondria membrane potential (ΔΨm). Moreover, the compound was able to inhibit more than 90 % of macrophage-released amastigote differentiation into promastigote forms with IC₅₀ of 0.069 ± 0.04 μg/mL. Conversely, the essential oil did not induce relevant cytotoxicity, presenting no harmful effects to the host cell after 48h (CC₅₀ > 0.1 μg/mL).

Overall, the results presented herein show the initial and promising use of S. molle essential oil as chemotherapy against the L. (L.) amazonensis parasite, and consequently against cutaneous and diffuse cutaneous leishmaniasis.