QUINOLINE ANTIMALARIAL-DRUGS INHIBIT SPONTANEOUS FORMATION OF BETA-HEMATIN (MALARIA PIGMENT)

Polymerisation of haematin to beta-haematin (haemozoin or malaria pigm ent) in acidic acetate solutions was studied using infrared spectrosco py. The reaction was found to occur spontaneously between 6 and 65 deg rees C, in 0.1-4.5 M acetate and pH 4.2-5.0. The anti-malarial drugs q uinine, chloroquine and amodiaquin were found to block spontaneous bet a-haematin formation, while the anti-malarially inactive 9-epiquinine and 8-hydroxyquinoline had no effect on the reaction, as did primaquin e, a drug which is active only against exo-erythrocytic stages of infe ction. It is argued that the intra-erythrocytically active anti-malari al agents act by binding to haematin, blocking beta-haematin formation and leaving toxic haematin in the parasite food vacuoles.