UPLC-MS/MS Based Identification of Dietary Steryl Glucosides by Investigation of Corresponding Free Sterols

Abstract

Dietary plant foods are characterized by a vast molecular diversity of glycosylated sterols (SG) that differ in the structure of the steryl backbone. The identification of these polar steryl conjugates represents a major challenge as they are structurally highly similar, and commercial standards are limited to a few naturally abundant species. Spectral databases do not yet contain MS/MS spectra of these sterol conjugates obtained by electrospray ionization (ESI), which would facilitate their reliable identification. Thus, this study aimed at providing novel information on ESI-MS/MS spectra of both abundant and minor SG found in foods. As a first step, however, free sterols (FS) were investigated for their fragmentation behavior as they share the same intermediate ion as SG. Pure SG were obtained from commercially available standard mixtures and minor SG were extracted from different food sources (oat bran, wheat bran, pumpkin seeds, melon, rapeseeds, and potato peel). ESI-MS/MS spectra of 15 FS were assessed and fragment ions reflective of structural features were identified and rationalized. Subsequently, 14 SG were identified at four different levels, while relative retention times from chromatographic separation and spectral features of FS served to identify five SG. Spectral data from FS were directly transferable to SG when analyzed as aglycone ions as shown by similarity scores while SG were characterized by shorter retention times in reverse phase chromatography and the additional analysis as sodiated adduct confirmed their glycosidic nature. Moreover, we report for the first time the occurrence of 24-methylenecholesterol and a 4-monomethyl sterol as glycosidic conjugates in higher plants. The presented data will serve as a valuable tool for SG profiling of foods by facilitating their identification.

Detection of ergosterol using liquid chromatography/electrospray ionization mass spectrometry: Investigation of unusual in‐source reactions

“…Potential fragmentation pathways of ergosterol and ergosterol analogues as observed by MS/MS experiments conducted with an IT‐TOF mass spectrometer, and in accordance with the fragmentation mechanisms reported in the literature 33 [Color figure can be viewed at wileyonlinelibrary.com]…”

“…Typical fragmentations in accordance with the literature including loss of water or fragmentations on the side chain were observed for most ion species (Figure 5; and supporting information S4–S8). 33 The fragmentation pattern shows that, when oxidation is due to oxygen addition, no loss corresponding to oxidation of the side chain could be observed, indicating that only the cyclic moiety is involved. Moreover, when highly oxidized species were formed in the source, other specific fragmentations were observed such as additional losses of 2 u (H 2 ), 18 u (H 2 O), 28 u (CO), 32 u (O 2 ) or 60 u.…”

Metabolite Profiling of Aquilaria malaccensis Leaf Extract Using Liquid Chromatography-Q-TOF-Mass Spectrometry and Investigation of Its Potential Antilipoxygenase Activity In-Vitro

“…Two plant-derived sterols were detected in the sample on the positive ionization mode. The characteristic MS/MS spectra that have been obtained from free sterols occur as [M+H-H2O] + [70].…”

Systematic Characterization and Identification of Saikosaponins in Extracts From Bupleurum marginatum var. stenophyllum Using UPLC-PDA-Q/TOF-MS

“…It is tedious to purify, separate, and identify them using conventional phytochemical separation methods, and the experimental period is long. In recent years, ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) has been widely used in many research fields due to its ability to obtain abundant sample information and efficient component separation, such as rapid identification of chemical components of TCM and drug quality control, speculated by aligning MS information and fragmentation patterns of target compounds with chemical standard substances or literature; the chemical components of TCM can be rapidly and accurately identified ( Guo et al, 2016 ; Qing et al, 2017 ; Münger et al, 2018 ; Yang et al, 2019 ; Ye et al, 2019 ; Xia et al, 2021 ). At present, there are still many saikosaponins with structural diversity present at low abundance that remain to be separated and identified by UPLC-MS.…”