Identification of flavone C-glycosides including a new flavonoid chromophore from barley leaves (Hordeum vulgare L.) by improved NMR techniques.
Six flavone C-glycosides were isolated from young leaves of barley. One of the C-glucosides has a new type of nucleus, a 2',4',5,5', 7-penta-OH-substituted flavone bearing a 6-C-beta-D-glucoside, which has apparently never been isolated before. One mono- and two di-C-glycosyl flavones were isolated for the first time from barley and identified as isoscoparin 7-O-beta-D-glucoside, carlinoside, and shaftoside, respectively. Other flavones were 7-O-beta-D-glucosides of isoorientin and isovitexin. The known problematic NMR structure elucidation of C-glycosyl flavonoids has been solved by using both a temperature close to the freezing point of the solvent (22.5 degrees C in DMSO-d(6)) and a high temperature (70, 90 degrees C) for comparison during NMR measurements. Structural determination of all the compounds was achieved by employing 1D and 2D NMR techniques.
Norbaek
R
R
Danish Institute of Agricultural Sciences, Department of Fruit, Vegetable and Food Science, Kirstinebjergvej 10, DK-5792 Aarslev, Denmark. rikke.norbaek@agrsci.dk
Brandt
K
K
Kondo
T
T
D005419:Flavonoids / Q000737:chemistry*; D006027:Glycosides / Q000032:analysis* / Q000737:chemistry; D001467:Hordeum / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D018515:Plant Leaves / Q000737:chemistry
D005419:Flavonoids; D006027:Glycosides