Biosynthesis of brassinosteroids in cultured cells of Catharanthus roseus

Precursor administration experiments with H-2-labeled 6-oxocampestanol, 6-droxocastasterone and 6 alpha-hydroxycastasterone in cultured cells of Catharanthus roseus were performed and the metabolites were analyzed by GC-MS. [H-2(6)]Cathasterone was identified as a metabolite of [H-2(6)]6-oxocampestanol. whereas [H-2(6)]6 alpha-hydroxycastasterone and [H-2(6)]castasterone were identified as metabolites of [H-2(6)]6-deoxocastasterone, and [H-1(6)]castasterone was identified as a metabolite of [H-2(6)]6 alpha-hydroxycastasterone, indicating that 6-deoxocastasterone is converted to castasterone via 6 alpha-hydroxycastasterone. In addition, 6-deoxocathasterone, a putative biosynthetic intermediate in the late C6-oxidation pathway, was identified as an endogenous brassinosteroid. These studies provide further evidence supporting our proposed biosynthetic pathways for brassinolide. (C) 2000 Elsevier Science Ltd. All rights reserved.