Rafał Frański1, Błażej Gierczyk1, Tomasz Kozik1, Łukasz Popenda2, Monika Beszterda3. 1. Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614, Poznań, Poland. 2. NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614, Poznań, Poland. 3. Department of Food Biochemistry and Analysis, Poznan University of Life Sciences, Mazowiecka 48, 60-623, Poznań, Poland.
Abstract
RATIONALE: The main feature of the fragmentation of [M - H]- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH3 ]-• product ion). Subsequent decomposition of [M - H - CH3 ]-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids. METHODS: Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument. RESULTS: A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking. CONCLUSIONS: The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH3 ]-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.
RATIONALE: The main feature of the fragmentation of [M - H]- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH3 ]-• product ion). Subsequent decomposition of [M - H - CH3 ]-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids. METHODS: Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument. RESULTS: A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking. CONCLUSIONS: The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH3 ]-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.
Authors: Saied A Aboushanab; Vadim A Shevyrin; Grigory P Slesarev; Vsevolod V Melekhin; Anna V Shcheglova; Oleg G Makeev; Elena G Kovaleva; Ki Hyun Kim Journal: Plants (Basel) Date: 2022-03-10