Study on the fragmentation pattern and identification of new compounds of characteristic pharmacological flavonoids in Epimedium based on high-resolution mass spectrometry
Epimedium was first recorded in the “Shennong Bencao Jing” and is the dried leaf of the Epimedium L. plant in the Berberidaceae genus. It has a warm nature, a spicy and sweet taste, and belongs to the liver and kidney meridians. Has the effects of tonifying kidney and yang, strengthening muscles and bones, dispelling wind and dampness; Clinically, it is commonly used to treat male infertility, osteoporosis and other diseases. The material basis of Epimedium has been relatively clear, and the main active ingredients are flavonol derivatives with demethylated icariin as the parent nucleus, such as icariin, icariin, and icariin, which have been widely reported in research. The author found through literature review that the active groups of this type of compound are hydroxyl groups at C-3, C-7, and C-4 ‘positions, as well as isopentenyl groups at C-8 position. A total of 54 structurally active secondary metabolites have been formed through methyl transfer reaction, sugar transfer reaction, redox reaction, etc. So far, there have been numerous reports on the mass spectrometry fragmentation of flavonoid glycosides, but there is no literature that combines the chemical structure of characteristic components of Epimedium with the mass spectrometry fragmentation rules for in-depth exploration. In this experiment, high-resolution mass spectrometry was used to classify the characteristic pharmacological flavonols in Epimedium into five categories: aglycones, monoglycosides, diglycosides, tri glycosides, and tetra glycosides. The experimental results are helpful for the qualitative and quantitative analysis of such components and the structural identification of new compounds, providing scientific basis for further clarifying the pharmacological substance basis and biosynthetic laws of Epimedium.

Epimedium is a commonly used and important tonic Chinese medicinal herb in China. Although there have been many reports on the pharmacological substance basis of Epimedium, there is currently no literature analyzing and summarizing the chemical structure and mass spectrometry fragmentation rules of this component, which is not conducive to the qualitative and quantitative analysis of this component, the exploration of biosynthetic rules, and the identification of new components and compounds. This study used high-resolution mass spectrometry to experimentally analyze the secondary mass spectrometry of compounds containing isopentenyl pharmacodynamic flavonols. It was found that these compounds would first break the C-3 glycosidic bond and acetyl group from the outside to the inside in the ESI source mass spectrometry, followed by the breaking of the C-7 glycosidic bond and acetyl group from the outside to the inside, and then the removal of the C-8 isopentenyl group and the C-4 ‘methoxy group. If the C-8 isopentenyl double bond is reduced to an isopentenyl group by water addition, its mass spectrometry fragmentation behavior will first dehydrate and then remove the alkyl group. If the C-8 group forms a ring with the C-7 group, the characteristic fragment of the isopentenyl group will not be produced. The chemical structures of two new compounds were identified based on the above fragmentation rules, but there are certain deficiencies in the ability of high-resolution mass spectrometry to identify the structures of isomers. The chemical structures of the new compounds still need to be determined by nuclear magnetic resonance spectroscopy after plant separation. According to literature reports, the C-3 hydroxyl group containing isopentenyl flavonols in Epimedium plants is an important active site, indicating that glycosylation of the C-3 hydroxyl group is more likely to occur. Correspondingly, the glycosidic bond at this site is also more easily broken in mass spectrometry behavior. Glycoside bonds belong to heterolysis in mass spectrometry fragmentation, which means that the charge is unevenly distributed during fragmentation. Therefore, the dipole moment size of glycosidic bonds in this type of derivative may be an important factor determining the difficulty of fragmentation, which needs further research and verification by the research group. The results of this experiment provide a scientific basis for further elucidating the pharmacological substance basis and biosynthetic laws of Epimedium.