Isolation and characterization of the new iridoid 10-hydroxy-(5 alpha H)-6-epidihydrocornin from Penstemon secundiflorus (Scrophulariaceae) is described. In biosynthetic experiments, deoxyloganic acid was incorporated into the transfused iridoid glycosides (5 alpha H)-6-epidihydrocornin and 10-hydroxy-(5 alpha H)-6-epidihydrocornin in P. secundiflorus. Formation of the trans-fused compounds is therefore a late event in the biosynthesis and does not occur during iridoid formation by cyclization of the open chain monoterpene precursor. In the same plant, 8-epideoxyloganic acid was not incorporated into the trans-iridoids. Deoxyloganic acid was also incorporated into 10-hydroxyhastatoside (which bears an 8 beta-methyl group), while 8-epideoxyloganic acid was incorporated into penstemoside (with an 8 alpha-methyl group). Thus, iridoid biosynthetic pathways leading from both deoxyloganic acid and 8-epideoxyloganic acid were found in the same plant.
biosynthesis, taxonomy, Scrophulariaceae, iridoid glucosides, Penstemon secundiflorus, 10-hydroxy-(5 alpha H)-6-epidihydrocornin
NCBI PubMed ID: 9862136Publication DOI: 10.1016/s0031-9422(98)00323-9Journal NLM ID: 0151434Publisher: Elsevier
Institutions: Department of Organic Chemistry, The Technical University of Denmark, Lyngby, Denmark, Department of Chemistry, Colorado State University, Fort Collins, US
Methods: 13C NMR, 1H NMR, HPLC, extraction, ROESY, HMQC, COSY, HR-FAB-MS, VLC
Found