<i>Plasmodium falciparum</i> Ferredoxin-NADP⁺ Reductase-Catalyzed Redox Cycling of Plasmodione Generates Both Predicted Key Drug Metabolites: Implication for Antimalarial Drug Development

Plasmodione (PD) is a potent antimalarial redox-active 3-benzyl-menadione acting at low nanomolar range concentrations on different malaria parasite stages. The specific bioactivation of PD was proposed to occur via cascade redox reactions starting from one-electron reduction and then benzylic oxidation, leading the generation several key metabolites including corresponding alcohol (PD-bzol, for benzhydrol) 3-benzoylmenadione (PDO, oxide). In this study, we showed that oxidation closely related formation semiquinone radical, which can be produced under two conditions: UV photoirradiation or catalysis by Plasmodium falciparum apicoplast ferredoxin–NADP+ reductase (PfFNR) cycling in presence oxygen parent PD. Electrochemical properties both were investigated DMSO water. single-electron potential values PD, PD-bzol, PDO, series 3-benzoylmenadiones determined according ascorbate kinetics. These compounds possess enhanced reactivity toward PfFNR as compared with model quinones. Optimal conditions set up obtain best conversion metabolites. irradiation isopropanol positive pressure led an isolated yield 31% PDO through transient species formed reactions. PfFNR, PD-bzol could observed during long lasting continuously fueled NADPH regenerated enzymatic system. Finally, quantified effect production oxidative stress transgenic 3D7[Api-roGFP2-hGrx1] P. parasites using described genetically encoded glutathione sensor hGrx1-roGFP2 methodology. fast reactive (ROS) pulse released mediated catalyzed PfFNR.