Flavone C-Glycoside, Phenolic Acid, and Nitrogen Contents in Leaves of Barley Subject to Organic Fertilization Treatments

From the leaves of barley, Hordeum vulgare, one new flavone C-glucoside and three known flavone glucosides were isolated and characterized by 1H and 13C NMR and MALDI-TOF-MS. The novel flavone C-glucoside was isovitexin 7-O-β-[6' ''-O-(E)-p-coumaroyl]glucoside (6' ''-coumaroylsaponarin), and the known compounds were isovitexin 7-O-β-[6' ''-O-(E)-feruloyl]glucoside, isoorientin 7-O-β-[6' ''-O-(E)-feruloyl]glucoside, and tricin 7-O-β-glucoside. The sum of all the flavone glycosides and soluble phenolic acids in the leaves decreased with increased rate of plant nutrients given in animal manure and with increased crop yield. All of the major phenylpropanoids showed the same general response to nutrient level. The concentration of nitrogen in the leaves was not directly related to nutrient application or to contents of phenylpropanoids. Keywords: Barley; Hordeum vulgare; C-glycosyl flavones; phenolic acids; nitrogen; Askov Long-Term Experiments