New lycorine-type alkaloid from Lycoris traubii and evaluation of antitrypanosomal and antimalarial activities of lycorine derivatives.

A new lycorine derivative LT1 (4) was isolated from the aerial part and bulbs of Lycoris traubii Hayward (Amaryllidaceae). Its structure including absolute configuration was established by spectroscopic analysis and semi-synthesis to be 1-O-(3'S)-hydroxybutanoyllycorine. Some lycorine ester derivatives including LT1 were examined for their inhibitory activity against Trypanosoma brucei brucei, the parasite associated with sleeping sickness, and against Plasmodium falciparum, the causative agent of malaria. Among them, 2-O-acetyllycorine (6) showed the most potent activity against parasitic T. b. brucei, and LT1 (4), 1-O-(3'R)-hydroxybutanoyllycorine (8), 1,2-di-O-butanoyllycorine (11), and 1-O-propanoyllycorine (12) showed significant activity against P. falciparum in an in vitro experiment.