title: Structural characterization of flavonol 3,7-di-O-glycosides and determination of the glycosylation position by using negative ion electrospray ionization tandem mass spectrometry.
abstract: Flavonol 3,7-di-O-glycosides were investigated by negative ion electrospray ionization tandem mass spectrometry using a quadrupole linear ion trap (LIT) mass spectrometer. The results indicate that the fragmentation behavior of flavonol 3,7-di-O-glycosides is substantially different from that of their isomeric mono-O-diglycosides. In order to characterize a flavonoid as a flavonol 3,7-di-O-glycoside, both [Y3(0) - H]-* and [Y(0) - 2H]- ions should be present in [M - H]- product ion spectrum. The MS(3) product ion spectra of Y3(0)-, [Y3(0) - H]-* and Y7(0)- ions generated from the [M - H]- ion provide sufficient structural information for the determination of glycosylation position. Furthermore, the glycosylation positions are determined by comparing the relative abundances of Y3(0)- and Y7(0)- ions and their specific fragmentation patterns with those of flavonol mono-O-glycosides. In addition, a [Y3(0) - H]-* ion formed by the homolytic cleavage of 3-O glycosidic bond with high abundance points to 3-O glycosylation, while a [Y(0) - 2H]- ion formed by the elimination of the two sugar residues is consistent with glycosylation at both the 3-O and 7-O positions. Investigation of negative ion ESI-MS(2) and MS(3) spectra of flavonol O-glycosides allows their rapid characterization as flavonol 3,7-di-O-glycoside and their differentiation from isomeric mono-O-diglycosides, and also enables their direct analysis in crude plant extracts.
authors.affiliation: Key Laboratory of Bioactive Substances and Resource Utilization of Chinese Herbal Medicine, Ministry of Education, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China.
authors.forename: Keyume
authors.initials: K
authors.lastname: Ablajan
authors.forename: Zeper
authors.initials: Z
authors.lastname: Abliz
authors.forename: Xiao-Ya
authors.initials: XY
authors.lastname: Shang
authors.forename: Jiu-Ming
authors.initials: JM
authors.lastname: He
authors.forename: Rui-Ping
authors.initials: RP
authors.lastname: Zhang
authors.forename: Jian-Gong
authors.initials: JG
authors.lastname: Shi
mesh_terms: D044948:Flavonols / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry*; D006031:Glycosylation; D010936:Plant Extracts / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D044948:Flavonols; D006027:Glycosides; D010936:Plant Extracts