Screening and HPLC-Based Activity Profiling for New Antiprotozoal Leads from European Plants

Based on a survey of remedies used in Renaissance Europe to treat malaria, we prepared and screened a library of 254 extracts from 61 plants for antiplasmodial activity in vitro. HPLC-based activity profiling was performed for targeted identification of active constituents in extracts. One of the most remarkable results was the identification of onopordopicrin, a germacranolide sesquiterpene lactone isolated from Arctium nemorosum as a potent inhibitor of P. falciparum with an IC₅₀ of 6.9 μM. It was tested similarly against Trypanosoma brucei rhodesiense, the parasite which causes African sleeping sickness. With an IC₅₀ of 0.37 μM, onopordopicrin was one of the most potent natural products reported so far. Cytotoxicity was determined against rat myoblast L6 cells (IC₅₀: 3.06).