Antiparasitic Activity of Some Xanthones and Biflavonoids and Identification of a New Biflavanoid from the Root Bark of Garcinia livingstonei

A new biflavanoid, ent -naringeninyl-(I-3,II-8)-4'- O -methylnaringenin ( 1 ), along with five known xanthones and two known biflavonoids, (+)-volkensiflavone and (+)-morelloflavone, was isolated from the root bark of Garcinia livingstonei (Clusiaceae) T. Anders., collected in Tanzania. The absolute configuration of 1 was established by CD spectroscopy. This compound showed a moderate activity against P. falciparum (IC 50 6.0±1.7µM). Antitrypanosomal activity (IC 50 0.87±0.23µM) was observed for 1,4,5-trihydroxy-3-(3-methylbut-2-enyl)-9 H -xanthen-9-one. The dimeric xanthone garcilivin A showed a higher and non-selective antiparasitic activity and cytotoxicity (IC 50 2.0±0.1µM against MRC-5 cells) than its diastereoisomer garcilivin C (IC 50 52.3±5.5µM).