Antiparasitic activity of some xanthones and biflavonoids from the root bark of Garcinia livingstonei

A new biflavanoid, ent-naringeninyl-(I-3 alpha,II-8)-4'-O-methylnaringenin (6), along with five known xanthones and two known biflavonoids, was isolated from the root bark of Garcinia livingstonei collected in Tanzania. The absolute configuration of 6 was established by CD spectroscopy. This compound showed moderate activity against P. falciparum (IC50 6.7 mu M). Antitrypanosomal activity (IC50 0.87 mu M) was observed for 1,4,5-trihydroxy-3-(3-methylbut-2-enyl)-9H-xanthen-9-one (3). The dimeric xanthone garcilivin A (4) showed a higher and nonselective antiparasitic activity and cytotoxicity (IC50 2.0 mu M against MRC-5 cells) than its diastereoisomer garcilivin C (5) (IC50 52.3 mu M).