Iridoid glycoside biosynthesis in Penstemon secundiflorus. Another H-5, H-9 trans-iridoid glycoside.
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 trans-fused 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.
Krull
R E
RE
Department of Chemistry, Colorado State University, Fort Collins 80523, USA.
Stermitz
F R
FR
Franzyk
H
H
Jensen
S R
SR
D005960:Glucosides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D039823:Iridoids; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010944:Plants / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D005960:Glucosides; D039823:Iridoids; D011714:Pyrans