Effect of physostigmine on Plasmodium falciparum in culture

Human erythrocytes contain 7 electrophoretically different alpha-naphthyl acetate esterases. Their solubility properties indicate that 5 are present in the erythrocyte cytoplasm and 2 are tightly bound to the stroma; the stroma-bound esterases can be inhibited by 10(-5) M physostigmine. No additional physostigmine-sensitive enzymes were detectable in Plasmodium falciparum-infected cells. Addition of physostigmine to malaria parasites in culture killed the parasites rapidly.