2-Phenoxy-3-Trichloromethylquinoxalines Are Antiplasmodial Derivatives with Activity against the Apicoplast of .

The malaria parasite harbors a relict plastid called the apicoplast. Although not photosynthetic, the apicoplast retains unusual, non-mammalian metabolic pathways that are essential to the parasite, opening up a new perspective for the development of novel antimalarials which display a new mechanism of action. Based on the previous antiplasmodial hit-molecules identified in the 2-trichloromethylquinoxaline series, we report herein a structure-activity relationship (SAR) study at position two of the quinoxaline ring by synthesizing 20 new compounds. The biological evaluation highlighted a hit compound () with a potent K1 EC value of 0.2 µM and a HepG2 CC value of 32 µM (Selectivity index = 160). Nitro-containing () was not genotoxic, both in the Ames test and in vitro comet assay. Activity cliffs were observed when the 2-CCl group was replaced, showing that it played a key role in the antiplasmodial activity. Investigation of the mechanism of action showed that presents a drug response by targeting the apicoplast and a quick-killing mechanism acting on another target site.