Differentiation of Interglycosidic Linkages in Permethylated Flavonoid Glycosides from Linked-Scan Mass Spectra (B/E)

Abstract

A series of per-O-methylated flavonoid di- and tri-glycosides, linked with 1-2 and/or 1-6 glycosidic bonds between sugar rings that were isolated from different plant materials were analyzed. It was demonstrated that the fragmentation behavior of permethylated flavonoid glycosides is dependent on the glycosidic bond placement between sugars. Y(n) type fragment ions, created after glycosidic bond cleavage with oxygen retention on sugar at the reducing end for permethylated compounds, were observed in the normal and linked-scan mass spectra recorded for alpha(1-2) bonded conjugates of flavonoid di- and tri-glycosides. Moreover, for alpha (1-6) linked glycosides, Y fragments created after rearrangement and elimination of internal sugar residues were observed in addition to Y(n) type ions, but these fragment ions were not registered in normal desorption ionization spectra. This second type of fragmentation was also reported previously in collision-induced dissociation tandem mass spectrometry (CID MS/MS) spectra of some oligosaccharides and flavonoid glycosides, but their presence was independent of the glycosidic bonds placement between sugar rings.

Rapid differentiation of isobaric and positional isomers of structurally related glycosides from Phytolacca bogotensis

“…It has been reported that an internal sugar loss can occur in the MS n fragmentation of protonated α ‐hederin and other triterpenic saponins 27, 28. This unusual fragmentation was first described for oligosaccharides such as sialyl lewis and the flavonoid glycosides 29–34. Although these fragmentations were only described for the 1→2 and 1→6 glycosidic linkages, this phenomenon can be avoided by using alkali metal ion adducts (such as lithium and sodium), in order to confirm the real sugar sequence.…”

Structural characterization of flavonoid glycosides by multi‐stage mass spectrometry

“…According to their FAB and ESI data, a thorough study of some characteristic fragment intensities provided means of differentiation for hexose and pentose isomers. On the other hand, it was demonstrated that the fragmentation behavior of permethylated flavonoid glycosides (the experiments did not include flavanones) depended on the glycosidic linkage between the sugars units (Franski et al, 2002). Contrary to the non‐derivatized glycosides (see Section 4.5), the Y * ion was observed for both flavones and flavonols, but the rearrangement reaction yielding the Y * fragment occurred only for 1 → 6 linked disaccharides.…”

Characterization of flavonoids by aluminum complexation and collisionally activated dissociation

“…Tandem mass spectrometry (MS/MS) has been used to characterize the structures of flavonoids over the past decade 4–23. Collisionally activated dissociation (CAD) of conventional protonated or deprotonated flavonoids has had some notable success for extensive isomer differentiation, but there have also been some limitations, in large part because of common structural features of the flavonoids which promote similar dissociation routes 4–23. Protonated flavonoids typically give more distinctive fragmentation patterns than deprotonated flavonoids, but the ionization efficiencies of flavonoids in the positive mode are often rather low because flavonoids are acidic, not basic, compounds.…”