28-norcastasterone is biosynthesized from castasterone

Metabolic experiments with deuterium-labeled castasterone in seedlings of A rabidopsis thaliana, Oryza sativa and Lycopersicon esculentum, and cultured cells of Catharanthus roseus were performed, and the metabolites were anal yzed by GC-MS. In all the plans species examined. [H-2(3)]28-norcastasteron e was identified as a metabolite of [26,28-H-2(6)]castasterone, indicating that castasterone is the biosynthetic origin of 28-norcastasterone. Moreove r, the natural occurrence of 28-norcastasterone and 28-nortyphasterol in se edlings of A. thaliana has been demonstrated. This is the first report of t he natural occurrence of 28-nortyphasterol in plants. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.