Comparison of<i>in vitro</i>and<i>in vivo</i>antimalarial activities of g-phenanthrenecarbinols

Analysis of the antimalarial activity of a selected series of 17 9-phenanthrenecarbinols against cultured strains of Plasmodium falciparum and against P. berghei in mice following oral administration indicated that the rankings of activities within the series were influenced by substituents on the 9-carbinol and the route of administration. Compounds with alkylamino-alkyl groups were ranked as most active by an in vitro screening system which assayed activity against chloroquine-sensitive and chloroquine-resistant strains of cultured P. falciparum by the inhibition of uptake of radiolabelled hypoxanthine. There were few differences in ranking of activities between the two strains. Although there was a significant difference between activities of an erythro- and a threo-racemate, activities of the four optical isomers of this compound were comparable. Among the series, compounds with a 2-piperidyl substituent on the 9-carbinol were ranked most active by the oral route of administration as assayed by the cure rates of mice infected with P. berghei. Correlation of these observations with previously published data on the activity of these compounds against P. falciparum in Owl monkeys and P. berghei in mice following subcutaneous administration suggested that neither species of host nor strains of parasite significantly influenced the ranking of activities of this class of compound.