In vitro susceptibility of Trypanosoma brucei brucei to selected essential oils and their major components

Aiming for discovering effective and harmless antitrypanosomal agents, 17 essential oils and nine major components were screened for their effects on T. b. brucei. The essential oils were obtained by hydrodistillation from fresh plant material and analyzed by GC and GC-MS. The trypanocidal activity was assessed using blood stream trypomastigotes cultures of T. b. brucei and the colorimetric resazurin method. The MTT test was used to assess the cytotoxicity of essential oils on macrophage cells and Selectivity Indexes were calculated. Of the 17 essential oils screened three showed high trypanocidal activity (IC50 < 10 mu g/mL): Juniperus oxycedrus (IC50 of 0.9 mu g/mL), Cymbopogon citratus (IC50 of 3.2 mu g/mL) and Lavandula luisieri (IC50 of 5.7 mu g/mL). These oils had no cytotoxic effects on macrophage cells showing the highest values of Selectivity Index (63.4, 9.0 and 11.8, respectively). The oils of Distichoselinum tenuifolium, Lavandula viridis, Origanum virens, Seseli tortuosom, Syzygium aromaticum, and Thymbra capitata also exhibited activity (IC50 of 10-25 mu g/mL) but showed cytotoxicity on macrophages. Of the nine compounds tested, alpha-pinene (IC50 of 2.9 mu g/mL) and citral (IC50 of 18.9 mu g/mL) exhibited the highest anti-trypanosomal activities. Citral is likely the active component of C. citratus and a-pinene is responsible for the antitrypanosomal effects of J. oxycedrus. The present work leads us to propose the J. oxycedrus, C. citratus and L. luisieri oils as valuable sources of new molecules for African Sleeping Sickness treatment.