Antiprotozoal Activity of Plants Used in the Management of Sleeping Sickness in Angola and Bioactivity-Guided Fractionation of J.F.Gmel and L. Active against .

Folk medicine is widely used in Angola, even for human African trypanosomiasis (sleeping sickness) in spite of the fact that the reference treatment is available for free. Aiming to validate herbal remedies in use, we selected nine medicinal plants and assessed their antitrypanosomal activity. A total of 122 extracts were prepared using different plant parts and solvents. A total of 15 extracts from seven different plants exhibited in vitro activity (>70% at 20 µg/mL) against bloodstream forms. The dichloromethane extract of (leaves and leaflets) and the ethanolic extract of (leaves) had IC values ≤ 10 µg/mL. These two aquatic plants are of particular interest. They are being co-applied in the form of a decoction of leaves because they are considered by local healers as male and female of the same species, the ethnotaxon "longa dia simbi". Bioassay-guided fractionation led to the identification of eight active molecules: gallic acid (IC 0.5 µg/mL), methyl gallate (IC 1.1 µg/mL), 2,3,4,6-tetragalloyl-glucopyranoside, ethyl gallate (IC 0.5 µg/mL), 1,2,3,4,6-pentagalloyl-β-glucopyranoside (IC 20 µg/mL), gossypetin-7--β-glucopyranoside (IC 5.5 µg/mL), and hypolaetin-7--glucoside (IC 5.7 µg/mL) in , and 5-[(8Z,11Z,14Z)-heptadeca-8,11,14-trienyl] resorcinol (IC 5.3 µg/mL) not described to date in . Five of these active constituents were detected in the traditional preparation. This work provides the first evidence for the ethnomedicinal use of these plants in the management of sleeping sickness in Angola.