Antigiardial activity of triterpenoids from root bark of Hippocratea excelsa

Abstract

Two new triterpenoids, 21β-hydroxyolean-12-en-3-one (1) and a seco-dinor derivative of pristimerine named dzununcanone (2), were isolated from the root bark of Hippocratea excelsa. Their structures were assigned on the basis of spectroscopic evidence, mainly 1H and 13C 1D and 2D NMR including DEPT, COSY, ROESY, HSQC, and HMBC experiments, as well as EIMS and HREIMS. The known 21α-hydroxy-3-oxofriedelane (3), a compound new to the species, and the known methide quinones pristimerine (4) tingenone (5), and xuxuarine Eβ (7) were also isolated. The antiprotozoal activities were determined against Giardia intestinalis. Pristimerine and tingenone were the most active antigiardial compounds, with IC50 values of 0.11 and 0.74 μM, respectively, compared with metronidazole, the current drug of choice (IC50 1.23 μM). © 2007 American Chemical Society and American Society of Pharmacognosy.