Antiplasmodial activity of knipholone and related natural phenylanthraquinones

phenylanthraquinone knipholone (1) and three of its natural derivatives as well as seven structurally related but simplified compounds have been examined for their antiplasmodial activity against asexual erythrocytic stages of two strains of Plasmodium falciparum in vitro (K1/chloroquine-resistant and NF 54/chloroquine-sensitive). All the phenylanthraquinones showed considerable activity with only little cytotoxicity, while their anthraquinone and phenyl moieties were completely inactive. Knipholone (1) and its natural derivatives can therefore be considered as a new group of potential antimalarials