title: Laser-induced hydrogen radical removal in UV MALDI-MS allows for the differentiation of flavonoid monoglycoside isomers.
abstract: Negative-ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectra and tandem mass spectra of flavonoid mono-O-glycosides showed the irregular signals that were 1 and/or 2 Da smaller than the parent deprotonated molecules ([M - H](-)) and the sugar-unit lost fragment ions ([M - Sugar - H](-)). The 1 and/or 2 Da mass shifts are generated with the removing of a neutral hydrogen radical (H*), and/or with the homolytic cleavage of the glycosidic bond, such as [M - H* - H](-), [M - Sugar - H* - H](-), and [M - Sugar - 2H* - H](-). It was revealed that the hydrogen radical removes from the phenolic hydroxy groups on the flavonoids, not from the sugar moiety, because the flavonoid backbones themselves absorb the laser. The glycosyl positions depend on the extent of the hydrogen radical removals and that of the homolytic cleavage of the glycosidic bonds. Flavonoid mono-glycoside isomers were distinguished according to their TOF MS and tandem mass spectra.
authors.affiliation: Suntory Institute for Bioorganic Research, Shimamoto, Mishima, Osaka, 618-0001, Japan, yamagaki@sunbor.or.jp.
authors.forename: Tohru
authors.initials: T
authors.lastname: Yamagaki
authors.forename: Takehiro
authors.initials: T
authors.lastname: Watanabe
authors.forename: Masaki
authors.initials: M
authors.lastname: Tanaka
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Sugahara
mesh_terms: D005419:Flavonoids / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D007536:Isomerism; D007834:Lasers; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014466:Ultraviolet Rays
chemical_list: D005419:Flavonoids; D006027:Glycosides; D007477:Ions; D006859:Hydrogen