title: Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy.
abstract: Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single (13)C NMR spectrum of a betalain pigment, namely that of neobetanin (=14,15-dehydrobetanin), was available. Because of its sufficient stability under highly acidic conditions otherwise detrimental for betacyanins, this pigment remained an exemption. Since betalains are most stable in the pH range of 5-7, a new solvent system has been developed allowing improved data acquisition through improved pigment stability at near neutral pH. Thus, not only (1)H, but for the first time also partial (13)C data of betanin, isobetanin, phyllocactin and hylocerenin isolated from red-purple pitaya [Hylocereus polyrhizus (Weber) Britton & Rose, Cactaceae] could be indirectly obtained by gHSQC- and gHMQC-NMR experiments.
authors.affiliation: Institute of Food Technology, Section Plant Foodstuff Technology, Hohenheim University, Garbenstrasse 25, D-70599 Stuttgart, Germany.
authors.forename: Florian C
authors.initials: FC
authors.lastname: Stintzing
authors.forename: Jürgen
authors.initials: J
authors.lastname: Conrad
authors.forename: Iris
authors.initials: I
authors.lastname: Klaiber
authors.forename: Uwe
authors.initials: U
authors.lastname: Beifuss
authors.forename: Reinhold
authors.initials: R
authors.lastname: Carle
mesh_terms: D050858:Betalains; D029421:Cactaceae / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005638:Fruit / Q000737:chemistry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010860:Pigments, Biological / Q000737:chemistry* / Q000302:isolation & purification; D000644:Quaternary Ammonium Compounds
chemical_list: D010860:Pigments, Biological; D000644:Quaternary Ammonium Compounds; D050858:Betalains