Antitrypanosomal compounds from the leaf essential oil of Strychnos spinosa.

The composition of the essential oil obtained by hydrodistillation of the leaves of Strychnos spinosa (Loganiaceae) was analysed by GC-FID and GC-MS. Out of twenty-two compounds identified in the oil, the main constituents were palmitic acid (34.3%), linalool (16.0%), and (E)-phytol (6.7%). Since the leaves of this plant are used in African traditional medicine to treat African trypanosomiasis, we evaluated the in vitro activity of the essential oil as well as of 15 of its components on Trypanosoma brucei brucei bloodstream forms and on mammalian cells (J774 murine macrophages) to evaluate the selectivity of the antitrypanosomal effect. The essential oil was active on the parasites without a great selectivity [IC50 on T. b. brucei = 13.5 microg/mL with a selectivity index (SI) of 4.4]. (E)-Nerolidol, a minor component of the hydrodistillate, as well as linalool, were shown to have a more potent and selective effect on the trypanosomes [IC50 = 1.7 and 2.5 microg/mL (7.6 and 16.3 microM) with SI = 35.7 and > 40, respectively]. These two oxygenated terpenes have promising activity and it would be of interest to study their mechanism of action as well as their in vivo activity.