Antimalarial activity of the reference condition (AS 4 nM) and samples from (a) the permeation test using artesunate solution and (b) the permeation test using artesunate powder. Each sample was tested in triplicate. Data are presented as mean ± SD (n = 3). AS = artesunate; FU = fluorescence unit; Green dotted-line = threshold value for maximum parasite growth (fluorescence of parasites incubated without artesunate and KRB during the semi-quantitative test); Red dotted-line = threshold value for minimum parasite growth (parasite fluorescence at the beginning of the test).