title: Identification of acylated xanthone glycosides by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in positive and negative modes from the lichen Umbilicaria proboscidea.
abstract: The xanthoside composition of the crude extract of Umbilicaria proboscidea (L.) Schrader was characterized using LC-UV diode array detection and LC-atmospheric pressure chemical ionization (APCI) MS methods. The presence of acylated xanthone-O-glucosides was determined by both positive and negative ion LC-APCI-MS methods. Based on UV and MS spectral data and NMR spectroscopy, a total of 14 compounds (6-O-acylated umbilicaxanthosides A and B) were identified in U. proboscidea for the first time. In order to further develop the applicability of LC-MS techniques in phytochemical characterization, the effect of different ionization energy on fragmentation was studied using APCI. The optimal ionization conditions were achieved in positive ion APCI by using ammonium acetate buffer and in negative ion APCI by using formic acid (pH 4).
authors.affiliation: Institute of Microbiology, Vídenská 1083, Prague 14220 Czech Republic. rezanka@biomed.cas.cz
authors.forename: Tomás
authors.initials: T
authors.lastname: Rezanka
authors.forename: Valery M
authors.initials: VM
authors.lastname: Dembitsky
mesh_terms: D000215:Acylation; D001203:Ascomycota / Q000737:chemistry*; D001274:Atmospheric Pressure; D002853:Chromatography, Liquid / Q000379:methods*; D006027:Glycosides / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry / Q000379:methods*; D044004:Xanthones / Q000032:analysis*
chemical_list: D006027:Glycosides; D044004:Xanthones