Furofuranic glycosylated lignans: a gas‐phase ion chemistry investigation by tandem mass spectrometry

Abstract

Alkali metal cation adducts, [M+Alk](+), and [M-H](-) ions of four known glycosylated furofuran lignans, (+)-pinoresinol 4-O-beta-D-glucopyranoside, (+)-phylliroside, (+)-8-hydroxypinoresinol 4-O-beta-D-glucopyranoside, and (+)-8-hydroxypinoresinol 8-O-beta-D-glucopyranoside, recently isolated from Carex distachya, were generated by electrospray ionization and allowed to undergo collisionally activated dissociation (CAD) in a quadrupole ion trap (QIT) and in a triple quadrupole (TQ) mass spectrometer. CAD mass spectra of [M+Na](+) and [M+Li](+) adducts revealed the presence of structurally diagnostic product ions. CAD mass spectra of deprotonated glycosylated furofuran lignans showed the typical neutral loss of 162 Da when the glucose residue was bound to a phenolic oxygen atom. When glycosylation occurred at an alcoholic oxygen, as for (+)-8-hydroxypinoresinol 8-O-beta-D-glucopyranoside, a neutral loss of 180 Da represented the main fragmentation pathway. Selective hydrogen/deuterium (H/D) exchange of all the acidic hydrogen atoms of furofuran glycosides, performed by introducing lignan glycosides in D(2)O/CH(3)OD solutions, were employed to obtain information on the nature of the product ions generated during TQ/CAD processes. Energy-resolved TQ/CAD mass spectra of deprotonated lignan glycosides and their deprotonated aglycones were used in a qualitative way to infer information on the integrated energetic picture of CAD fragmentations and to investigate the mechanism of the predominant dissociation/isomerization processes. On the basis of the hypothesized fragmentation mechanisms, gas-phase features of the furofuran ring were derived. The presence of an OH substituent in the C8 position decreased the electron density in the adjacent C8' position, modifying the fragmentation pathway.

From the Collisionally Induced Dissociation to the Enzyme-Mediated Reactions: The Electron Flux Within the Lignan Furanic Ring

“…Useful information were obtained in the positive ion mode and CAD/MS spectra of [M+H] + ions and of alkali metal cation adducts were proposed for their rapid and unambiguous identification in plant extracts (Ricci et al, 2008;. The CAD mass spectra of glycosylated lignans coordinated to different alkali metal cations (Alk + , e.g.…”

“…Literature on mass spectrometric data concerning the fragmentation pattern of many plant secondary metabolites is almost limited to few classes of compounds. This issue represents the main object of our experimental research (Ricci et al, 2008;. In this chapter first we will focus on the structural investigation studies by tandem mass spectrometry of plant secondary metabolites belonging to the two classes of furofuranic lignans (FUR) and tetrahydrofuranic lignans (THF).…”

A tandem mass spectrometric investigation of the low‐energy collision‐activated fragmentation of neo‐clerodane diterpenes

“…The CAD mass spectrum of the [M–H] – ion of compound 1 ( m/z 507), shown in Fig. 2(a), is dominated by the presence of the aglycone ion at m/z 345, arising from the loss of 162 Da, probably through a mechanism well known for flavonoid O ‐glycosides,16 and also observed for other plant secondary metabolites such as furofuran lignan glucosides 19. This mechanism involves proton transfer from the sugar to the glycosidic oxygen atom and heterolytic cleavage of the glycosidic bond.…”

“…The coupling of high‐performance liquid chromatography (HPLC) with mass spectrometry (MS) is routinely used for the characterization of plant secondary metabolites and their glycosides in organic mixtures. In order to perform a rapid, accurate and reliable qualitative and/or quantitative analysis in plant extracts, alcoholic beverages, foods, biological fluids, etc., collision‐activated dissociation (CAD) mass spectra of precursor ions from an enormous variety of natural compounds such as flavonoids, flavonoid glycosydes,16 dibenzylbutyrolactone, dibenzocyclooctadiene and furofuran lignans17–20 have been employed.…”

Structural discrimination of isomeric tetrahydrofuran lignan glucosides by tandem mass spectrometry

“…Although the use of fragmentation patterns of lignans can prove helpful for their identification as well as for their quantification, the number of systematic investigations, aimed at furnishing guidelines for the interpretation of their CAD mass spectra, is yet limited and rather incomplete 18–24. Systematic studies dealt with the fragmentation pattern of lignans belonging to different sub‐classes,18, 19 or considered a particular lignan class such as dibenzylbutyrolactone,20 dibenzocyclooctadiene lignans,20–24 and furofuran lignans 9, 21, 25…”