Pteridanoside, the first protoilludane sesquiterpene glucoside as a toxic component of the neotropical bracken fern Pteridium aquilinum var. caudatum

Chromatographic fractionation, monitored by brine shrimp bioassay, led to t he isolation of the first protoilludane-type sesquiterpene glucoside, pteri danoside (5), from a bioactive hot-water extract of the neotropical bracken fern Pteridium aquilinum var. caudatum (Dennstaedtiaceae). The enzymatic h ydrolysis of 5 yielded its aglycon, pteridanone (6), and D-glucose. The abs olute stereostructure of 5 was confirmed by the CD spectroscopic analysis o f 6. Pteridanoside (5) exhibited toxicity (LC50 of 250 mu g/mL at 24 h and 62.5 mu g/ml at 48 h) toward brine shrimp, while the aglycon 6 did not. (C) 1999 Elsevier Science Ltd. All rights reserved.