Many plant and insect species of the tropical rainforests in western Uganda and eastern DR Congo have not yet been discovered; about 90% have never been screened for bioactivity. Approx. 60% of the world’s population relies almost entirely on plants for medication. The knowledge of African plants and their traditional uses are mainly transferred orally from one generation to the next by traditional healers, leading to the loss of vital information due to lack of records. Our study provides documentation of 16 different African medicinal plants, which are claimed to possess antimalarial, anti-cancer and antibiotic properties, amongst others. A possible methodology for the discovery of novel pharmacologically active drugs is the screening of selected plant extracts for a broad array of pharmacological activities.
We present results of diverse bioassays performed with 61 different plant extracts from these 16 selected plant species, including:
1. Antimalarial heme biocrystallization assay as a pre-screen for upcoming in vitro and in vivo evaluation,
2. Evaluation of antiplasmodial activity against chloroquine-resistant Plasmodium falciparum K1 strain,
3. Cytotoxicity testing with human MRC-5 lung fibroblast cells,
4. GC-MS-assisted Ames test with human S9 liver fractions for investigation of mutagenic / potential carcinogenic effects of the extracts.
Of all plants tested, diethyl ether extracts of Warburgia ugandensis showed the lowest IC50 value against P. falciparum K1 with 0.5
µ
g/ml. In many cases, the traditional use of the plant species could be scientifically validated. Bioassay-guided fractionations combined with GC/LC-MS techniques enabled identification of bioactive compounds in some of the tested African plants. For instance, extracts of Zanthozylum chalybeum contained 8% of lupeol that is known for its antiprotozoal activity in literature. This study was performed according to the international and national rules considering the Convention on Biodiversity and the Nagoya Protocol.