Electrospray ionisation mass spectrometric behaviour of flavonoid 5‐O‐glucosides and their positional isomers detected in the extracts from the bark of Prunus cerasus L. and Prunus avium L.

Abstract

Introduction Literature data concerning the electrospray ionisation mass spectrometry (ESI‐MS) behaviour of flavonoid 5‐O‐glycosides are poor and sometimes disputable. Therefore, we decided to analyse the compounds of this kind present in the bark of Prunus cerasus and Prunus avium by using high‐performance liquid chromatography HPLC/ESI‐MS. Objective The aim of this study is to obtain the comprehensive information about the ESI‐MS(+/−) behaviour of flavonoid 5‐O‐glucosides, to compare their behaviour with that of their positional isomers, to confirm that the known susceptibility of flavonoid 5‐O‐glucosides to hydrolysis may be successfully used for their identification. Method The bark from Prunus trees was extracted with pure methanol or, in order to perform hydrolysis and extraction simultaneously, with 5% methanolic solution of hydrochloric acid. The HPLC‐ESI‐MS analyses were performed using a Waters model 2690 HPLC pump and Waters/Micromass ZQ2000 mass spectrometer. Results Flavonoid 5‐O‐glycosides were completely hydrolysed under the acid conditions used, in contrast to their positional isomers. In positive ion mode, at low cone voltage, flavonoid 5‐O‐glycosides yield abundant Y0+ aglycone ions, in contrast to their positional isomers. In the negative ion mode, flavonoid 5‐O‐glycosides do not yield [Y0 − H]−· fragment ions, in contrast to their positional isomers. When aglycone contains only two hydroxyl groups, the flavonoid 5‐O‐glycosides can be detected in negative ion mode, whereas their positional isomers do not yield [M − H]− ions. Conclusion It has been demonstrated that the susceptibility to hydrolysis of the analysed compounds, the abundances of respective fragment ions formed, and their ESI(−) response allow unambiguous identification of flavonoid 5‐O‐glycosides and their differentiation from their positional isomers.

Extraction with Acidified Methanol—An Easy and Effective Method of Methyl Chlorogenate Formation, as Studied by ESI-MS

“…In both analyzed extracts we also detected flavonoid compounds, characteristic of Crataegus monogyna , e.g., hyperoside, vitexin-2′′- O -rhamnoside, quercetin (the latter only in the acid extract due to the partial hydrolysis of quercetin glycosides, [ 37 , 38 ]). Their identification was supported by the characteristic product ions [ 39 , 40 , 41 ], as shown in the supplementary material, Figures S3–S5 .…”

Seasonal Qualitative Variations of Phenolic Content in the Stem Bark of Prunus persica var. nucipersica ‐ Implication for the Use of the Bark as a Source of Bioactive Compounds

“…The main features allowing structure identification were: (i) 5‐O‐glycosides at low cone voltage that yielded very abundant Y 0 + ion, (ii) 3‐O‐glycosides that yielded abundant Y −. ion, (iii) abundant product ions formed as a result of the breaking of heterocyclic C‐ring were observed for flavanone glycosides in the positive ion mode, (iv) structures of all aglycones were identified in the hydrolyzed samples on the basis of characteristic product ions [2c,10] . The identification of flavanone conjugates (Table 1), including 5‐O‐glycosides (glycosylation of 5 position is rare in nature), is in good agreement with the observations reported by Rahman and Bhatnagar [2j].…”

“…The low amount of p ‐coumaroylsucrose conjugates containing 0–4 acetyl groups seems to be out of importance, since it is compensated by the tetra‐ and pentaacetylated conjugates, expected to show greater biological activity [13] . Taking into account the flavanone 5‐O‐glycosides content (5‐O‐glycosides, as easily hydrolyzing forms, [2c] may be of special interest with respect to their bioactivity) and catechin content it is clear that the September‐April period is the most appropriate. However, the lowered amount of rutin in this period surely is a disadvantage, since rutin is probably the flavonoid glycoside most widely used in pharmaceuticals, dietary supplements and cosmetics [14] .…”

Elucidation of glycosylation sites of kaempferol di‐O‐glycosides from methanolic extract of the leaves of Prunus domestica subsp. syriaca

“…In the positive ion mode, the loss of the sugar moiety from position 5 is very facile (easier than from position 3) and, in the negative ion mode, a homolytic cleavage occurs with very low efficiency. 14,19 None of the glycosides analyzed in this work meet these criteria; therefore, the glycosylation of position 5 can be excluded.…”