28-Norcastasterone is biosynthesized from castasterone

Abstract Metabolic experiments with deuterium-labeled castasterone in seedlings of Arabidopsis thaliana , Oryza sativa and Lycopersicon esculentum , and cultured cells of Catharanthus roseus were performed, and the metabolites were analyzed by GC–MS. In all the plant species examined, [ 2 H 3 ]28-norcastasterone was identified as a metabolite of [26,28- 2 H 6 ]castasterone, indicating that castasterone is the biosynthetic origin of 28-norcastasterone. Moreover, the natural occurrence of 28-norcastasterone and 28-nortyphasterol in seedlings of A. thaliana has been demonstrated. This is the first report of the natural occurrence of 28-nortyphasterol in plants.