Biosynthesis of salvinorin A proceeds via the deoxyxylulose phosphate pathway

a neoclerodane diterpenoid, isolated from the Mexican hallucinogenic plant Salvia divinorum, is a potent kappa-opioid receptor agonist. Its biosynthetic route was studied by NMR and HR-ESI-MS analysis of the products of the incorporation of [1-13C]-glucose, [Me-13C]-methionine, and [1-13C; 3,4-2H2]-1-deoxy-d-xylulose into its structure. While the use of cuttings and direct-stem injection were unsuccessful, incorporation of 13C into salvinorin A was achieved using in vitro sterile culture of microshoots. NMR spectroscopic analysis of salvinorin A (2.7 mg) isolated from 200 microshoots grown in the presence of [1-13C]-glucose established that this pharmacologically important diterpene is biosynthesized via the 1-deoxy-d-xylulose-5-phosphate pathway, instead of the classic mevalonic acid pathway. This was confirmed further in plants grown in the presence of [1-13C; 3,4-2H2]-1-deoxy-d-xylulose. In addition, analysis of salvinorin A produced by plants grown in the presence of [Me-13C]-methionine indicates that methylation of the C-4 carboxyl group is catalyzed by a type III S-adenosyl-l-methionine-dependent O-methyltransferase.