Antileishmanial Activity of Schinus terebinthifolia Essential Oil: Chemistry, In Vitro and Mechanistic Studies

Leishmaniasis is caused by parasitic protozoans of the Leishmania genus and has been classified as a Neglected Tropical Disease. Control of this parasite relies mainly on chemotherapy; however, conventional available drugs are unsatisfactory. Phytomedicine, particularly essential oils, is a promising alternative. In this study, the chemical composition and antileishmanial properties of essential oil from leaves of Schinus terebinthifolia Raddi (EO-St) were determined. Chemical components were identified by GC-MS. Antileishmanial activity on promastigotes of L. amazonensis was assayed, followed by the evaluation of the essential oil's effects on the mitochondrial membrane potential and redox state of the parasite. Finally, the activity was confirmed on intracellular amastigotes and compared with cytotoxicity on peritoneal macrophages from BALB/c mice. In the essential oil, 78 compounds were identified. The major component was δ-3-carene with 14.8%. The IC₅₀ values of 18.2 ± 1.4 µg/mL and 15.0 ± 1.6 µg/mL against promastigote and amastigote forms, respectively, were obtained. The cytotoxicity for the host cells was approximately four-fold higher than those for the parasite. The essential oil was able to cause a disruption in the mitochondrial membrane potential. The quantified redox parameters showed statistical differences (p < 0.05) between EO-St-treated cultures and control groups (untreated and treated with DMSO). In summary, EO-St was active in vitro against both forms of L. amazonensis, possible mediated by mitochondrial dysfunction and redox imbalance.