Fig. 3

Effects of combinations of cryptolepine with the artemisinin derivatives on Plasmodium falciparum growth in vitro (3D7 strain). Isobolograms show the effect of combinations of both cryptolepine with artemether (a), artesunate (b) and dihydroartemisinin (c). The interaction between cryptolepine and artesunate, artemether, or dihydroartemisinin against ring-stage parasites were determined using the SYBR Green I fluorescent-based drug sensitivity assay using the fixed ratio method. Each combination was set up in triplicate for 48 h. The FIC₅₀ concentrations were used in the plotting of the isobolograms