Sesquiterpene constituents in Petasites hybridus

The essential oil of the rhizomes of Petasites hybridus (Asteraceae) was investigated by gas chromatography, mass spectrometry, 1- and 2-dimensional NMR techniques and chemical correlations. Two new sesquiterpene hydrocarbons, petasitene and pethybrene, could be identified. Petasitene is the parent sesquiterpene hydrocarbon to the known norsesquiterpene albene. The absolute configuration of petasitene could be assigned by conversion of natural albene to petasitene by partial synthesis. Pethybrene is a tricyclic sesquiterpene hydrocarbon, which rearranges to the structurally related alpha-isocomene under acidic conditions. Several sesquiterpenes were isolated from the hydrodistillation products of Petasites hybridus and investigated by spectroscopic methods and chemical correlations. (C) 2002 Elsevier Science Ltd. All rights reserved.