1,4-naphthoquinone cations as antiplasmodial agents: hydroxy-, acyloxy-, and alkoxy-substituted analogues.

Cations of hydroxy-substituted 1,4-naphthoquinones were synthesized and evaluated as antiplasmodial agents against Plasmodium falciparum. The atovaquone analogues were found to be inactive as antagonists of parasite growth, which was attributed to ionization of the acidic hydroxyl moiety. Upon modification to an alkoxy substituent, the antiplasmodial activity was restored in the sub-100 nM range. Optimal inhibitors were found to possess IC50 values of 17.4-49.5 nM against heteroresistant P. falciparum W2.