Figure 2: Isobologram illustrating the in vivo interaction at the ED90 level between drug A (curcumin-piperine) with drug B (chloroquine) in Plasmodium chabaudi AS-3CQ chloroquine-resistant parasites. Plotting the percentage parasitemia inhibition versus the log dose of the drugs either alone and the drugs in combination using GraphPad Prism 4 software yielded a regression equation. The equation allowed the determination of the ED90 of the drugs alone and the drugs in combination. ED90 values were used to obtain isobolar equivalents (IE) [25, 26].