Afterwards, the compounds were distributed in a 3-fold serial dilution in 96-well plates before synchronized ring-stage parasites were seeded with a parasitemia of 0.05% in O Rh factor-positive erythrocytes and at a hematocrit of 1.5% in a total volume of 225 μL per well. After 72 h incubation at 50% inhibitory concentration (IC50) was determined by plotting normalized dose-response curves using nonlinear regression (Prism 7).