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Identification of common glycosyl groups of flavonoid O ‐glycosides by serial mass spectrometry of sodiated species
Author(s) -
Kite Geoffrey C.,
Veitch Nigel C.
Publication year - 2011
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.5154
Subject(s) - chemistry , aglycone , glycosyl , mass spectrometry , glycoside , disaccharide , chromatography , kaempferol , flavonoid , mass spectrum , stereochemistry , organic chemistry , antioxidant
Flavonoid O ‐glycosides are a ubiquitous and important group of plant natural products in which a wide variety of sugars are O ‐linked to an aglycone. Determining the identity of the sugars, and the manner in which they are linked, by mass spectrometry alone is challenging. To improve the identification of common O ‐linked di‐ and trisaccharides when analysing mixtures of flavonoid O ‐glycosides by liquid chromatography/mass spectrometry (LC/MS), the fragmentation of electrosprayed sodium adducts in an ion trap mass spectrometer was investigated. The sodium adducts [M + Na] + of kaempferol 3‐ O ‐glycosides generated sodiated glycosyl groups by the neutral loss of kaempferol. The product ion spectra of these sodiated glycosyl groups differed between four isomeric kaempferol 3‐ O ‐rhamnosylhexosides and four isomeric kaempferol 3‐ O ‐glucosylhexosides in which the primary hexose was either glucose or galactose and bore the terminal glucose or rhamnose at either C‐2 or C‐6. Fragmentation of sodiated glycosyl groups from linear O ‐triglucosides and branched O ‐glucosyl‐(1 → 2)‐[rhamnosyl‐(1 → 6)]‐hexosides produced sodiated disaccharide residues, and the product ion spectra of these ions assisted the identification of the complete sugar. The product ion spectra of the sodiated glycosyl groups were consistent among flavonoid O ‐glycosides differing in the position at which the sugar was O ‐linked to the aglycone, and the nature of the aglycone. The abundance of sodiated species was enhanced by application of a pre‐trap collision voltage, without the need to dope with salt, allowing automated LC/MS methods to be used to identify the glycosyl groups of common flavonoid O ‐glycosides, such as rutinosides, robinobiosides, neohesperidosides, gentiobiosides and sophorosides. Copyright © 2011 John Wiley & Sons, Ltd.