A fragmentation study of isoflavones in negative electrospray ionization by MSⁿ ion trap mass spectrometry and triple quadrupole mass spectrometry

Abstract

This study has elucidated the fragmentation pathway for deprotonated isoflavones in electrospray ionization using MS(n) ion trap mass spectrometry and triple quadrupole mass spectrometry. Genistein-d(4) and daidzein-d(3) were used as references for the clarification of fragment structures. To confirm the relationship between precursor and product ions, some fragments were traced from MS(2) to MS(5). The previous literature for the structurally related flavones and flavanones located the loss of ketene (C(2)H(2)O) to ring C, whereas the present fragmentation study for isoflavones has shown that the loss of ketene occurs at ring A. In the further fragmentation of the [M-H-CH(3)](-*) radical anion of methoxylated isoflavones, loss of a hydrogen atom was commonly found. [M-H-CH(3)-CO-B-ring](-) is a characteristic fragment ion of glycitein and can be used to differentiate glycitein from its isomers. Neutral losses of CO and CO(2) were prominent in the fragmentation of deprotonated anions in ion trap mass spectrometry, whereas recyclization cleavage accounted for a very small proportion. In comparison with triple quadrupole mass spectrometry, ion trap MS(n) mass spectrometry has the advantage of better elucidation of the relationship between precursor and product ions.

Current trends in isolation, separation, determination and identification of isoflavones: A review

“…6A. A study dealing with the fragmentation of isoflavones in negative electrospray ionization was presented by Kang et al [66] and information about the fragmentation of glucosides were published in [9] (fragmentation of glucosidic conjugates of irilone is shown in Fig. 6B).…”

Identification of metabolites of Danggui Buxue Tang in rat urine by liquid chromatography coupled with electrospray ionization time‐of‐flight mass spectrometry

“…29,33 Furthermore, it has been well documented that P10 could be metabolized to daidzein, 34 and then to equol (C 15 H 14 O 3 ).…”

Phytochemical analysis of isoflavonoids using liquid chromatography coupled with tandem mass spectrometry

“…In case of glucosides, the loss of the malonyl, acetyl and glucosyl groups are common fragmentation reactions that are very valuable for the structural elucidation of isoflavonoids conjugates (Wu et al 2003). Using multistage fragmentation experiments (MS n ), Kang et al (2007) investigated the fragmentation mechanism in negative ion mode and the predominant fragments were neutral losses of CO, CO 2 , C 3 O 2 and C 2 H 2 O (Kang et al 2007). Even though fragments resulting from rDA reaction were found in much lower abundance, they were in particular useful for structural elucidation as they allowed not only the determination of -OH groups on different rings, but also to identify the position of glucosidic bonds using fragments with intact glycoside bonds.…”