Multi-Frequency High-Field EPR Study of Iron Centers in Malarial Pigments

Malaria, whose most severe form is caused by a protozoan parasite, Plasmodium falciparum (Pf), remains the world’s most prevalent vector-borne disease. The spread of chloroquine-resistant strains (CQR) of Pf and the absence of a suitable replacement for this once effective antimalarial created an urgent need to understand the biochemistry behind the drug’s action.1 The intraerythrocytic growth stage of Pf involves hemoglobin proteolysis as the primary nutrient source with the concomitant release of free heme. The liberated heme is detoxified by the parasite into an inert crystalline material, called malarial pigment, or hemozoin.2,3 According to the recent hypothesis, chloroquine inhibits heme aggregation in ring or early-stage malaria trophozoites.4 It has been shown that hemozoin is chemically,2,5 spectroscopically,2,3 and crystallographi-cally6 identical and isostructural to its synthetic phase, â-hematin. The magnetic susceptibility measurements and Mössbauer spec