Triterpenes from Warszewiczia coccinea (Rubiaceae) as inhibitors of acetylcholinesterase.

Seventy-six plant extracts from the Panamanian flora have been screened for acetylcholinesterase (AChE) inhibitors by thin-layer chromatography (TLC) bioautography. The most promising extracts with AChE inhibitory and free radical scavenging activities at 100 microg were those of Tabernaemontana panamensis (Markgr., Boiteau & L. Allorge) Leeuwenb., Pentagonia macrophylla Benth., and Warszewiczia coccinea (Vahl) Klotzsch. Bioguided fractionation of W. coccinea stem extract afforded two triterpenes, 3beta,6beta,19alpha-trihydroxy-urs-12-en-28-oic acid (1) and 3beta,6beta-dihydroxy-olean-12-en-28-oic acid (sumaresinolic acid) (2), with AChE inhibitory activity. Their structures were determined by spectroscopic methods. This is the first report of these bioactive triterpenes in W. coccinea.