Antitrypanosomal Constituents from <em>Brasenia schreberi</em> and <em>Nymphaea lotus</em> Used in a Single Herbal Preparation against Sleeping Sickness in Angola

Abstract

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 have selected nine medicinal plants and assessed their antitrypanosomal ac-tivity. 122 extracts were prepared using different plant parts and solvents. 15 extracts from seven different plants exhibited in vitro activity against Trypanosoma brucei rhodesiense bloodstream forms &amp;gt;70% at 20 µg/ml. The dichloromethane extract of Nymphaea lotus (leaves and leaflets) and the ethanolic extract of Brasenia schreberi (leaves) had IC50 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 (IC50 0.5 µg/ml), methyl gallate (IC50 1.1 µg/ml), 2,3,4,6-tetragalloyl-glucopyranoside, ethyl gallate (IC50 0.5µg/ml), 1,2,3,4,6-pentagalloyl-β-glucopyranoside (IC50 20µg/ml), gossypet-in-7-O-β-glucopyranoside (IC50 5.5µg/ml), and hypolaetin-7-O-glucoside (IC50 5.7µg/ml) in B. schreberi, and 5-[(8Z,11Z,14Z)-heptadeca-8,11,14-trienyl] resorcinol (IC50 5.3µg/ml) not described to date in N. lotus. 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.