Pteroside A2a New Illudane-Type Sesquiterpene Glucoside from Pteridium caudatum L. Maxon, and the Spectrometric Characterization of Caudatodienone

Abstract
Fractionation of an extract of Pteridium caudatum L. Maxon. (syn P. aquilinum L. Kuhn var.caudatum) which had earlier yielded the illudane-type sesquiterpene glucosides, ptaquiloside (1a), isoptaquiloside (1b), and caudatoside (1c) afforded a mixture containing 1a and two minor components. Preparative HPLC afforded ptaquiloside Z (1d) and a new pteroside glucoside (pteroside A2) (3e), which was identified using a combination of mass spectral and one- and two-dimensional NMR analyses. The 1H and 13C NMR and mass spectrometric characterization of caudatodienone (2b), an unstable dienone derived from the degradation of caudatoside (1c) in pyridine solution, and the GC-MS characterization of some pterosin-type degradation products produced by reacting this solution with cosolvents is also reported. Keywords: Pteridium aquilinum; Pteridium caudatum; bracken fern; illudane glucosides; caudatoside; ptaquiloside Z; caudatodienone; pteroside A2