In vitro anti-plasmodial activity

The compound was tested against a NF54 Plasmodium falciparum strain (chloroquine sensitive); the tests were done in triplicate. Continuous in vitro cultures of asexual erythrocytes stage of the parasite were maintained following the modified method of Trager and Jensen [23]. The viability of the parasite was evaluated by looking at the parasite lactate dehydrogenase activity, which was conducted following a modified method described by Makler et al. [24]. Test sample was made to a stock solution of 20 mg/ml in DMSO (100%). The stock solution was preserved at − 20 °C. Dilutions of the stock were made on the day of experimentation. Artesunate and chloroquine were the drugs of reference in the experiment.

Full dose–response was conducted on the test compound to find concentrations at which 50% of parasitic growth is inhibited (IC₅₀ value). Primary compound concentration for the trial was at 100 μg/ml, thereafter successively diluted to concentration twice as much in medium to produce ten measures with varying concentrations; minimum concentration being 0.2 μg/ml. Chloroquine initial concentration was at 1000 ng/ml. Solvent concentrations in which the infected red blood cells were subjected to, had no significant consequence on the viability of parasite. A non-linear dose–response curve fitting analysis was used to calculate the IC₅₀ values, with the version4.0 Graph Pad Prism software (Graph Pad Prism, Inc: San Diego, CA, USA, 1994–2003).