In vitro leishmanicidal activity of monoterpenes present in two species of Protium (Burseraceae) on Leishmania amazonensis.

Ethnopharmacological Relevance: Leishmaniasis is a neglected disease that affects millions of people around the world. Parasite resistance and the toxicity to the current treatments lead to the search for new effective molecules. Plants are widely used in traditional and indigenous medicine to treat different diseases. The oleoresin of the genus Protium, which is rich in volatile compounds active against different microorganisms, is among these plants.

Aim: The aim of this study was to evaluate the leishmanicidal potential of Protium altsonii (PaEO) and P. hebetatum (PhEO) (Burseraceae) oleoresins, as well as of three representative monoterpenes in their constitution: α-pinene, p-cymene and 1,8-cineole.

Materials And Methods: Protium altsonii (PaEO) and P. hebetatum (PhEO) oleoresins and three of their constituents were tested in vitro on promastigotes and amastigotes-infected macrophages in different concentrations. Their toxicity for macrophages was analyzed by XTT assay and phagocytic ability. It was evaluated the ability of the compounds to induce NO production on treated-macrophages using Griess reaction and the effect of them in lipid profile on treated-parasite through Thin Layer Chromatography.

Results: Our data showed that both essential oils have toxic effect on promastigotes and amastigotes of L. amazonensis in vitro in a dose-dependent manner. PaEO IC were 14.8 μg/mL and 7.8 μg/mL and PhEO IC were 0.46 μg/mL and 30.5 μg/m for promastigotes and amastigotes, respectively. Toxicity to macrophages was not observed at 50 μg/mL with both EOs. The compounds 1,8- cineole, α-pinene, and p-cymene inhibited amastigotes survival in a dose-dependent manner with IC of 48.4 μg/mL, 37 μg/mL, 46 μg/mL, respectively. Macrophage viability was around 90% even at 200 μg/mL and the phagocytic capacity was not altered in the treated-macrophages to up 50 μg/mL. The compounds were not able to modulate the nitric oxide production either at rest or LPS-activated macrophages. In addition, treated promastigote revealed an important change in their lipid profile after 48 h at 50 μg/mL in the presence of the compounds.

Conclusions: The results indicate that oleoresins of Protium genus are potent against Leishmania and α-pinene, p-cymene and 1,8-cineole have anti-Leishmania properties that could be explored in synergistic assays in order to develop new drug candidates.