New UHPLC-Q-Orbitrap MS/MS-based Library-comparison method simultaneously distinguishes 22 phytophenol isomers from Desmodium styracifolium

Isomers distinction has become a bottleneck of the emerging ultra-high-performance liquid chromatography coupled with hybrid quadrupole-orbitrap tandem mass spectrometry (UHPLC-Q-orbitrap MS/MS) technology. The present study thus used Desmodium styracifolium as model plant to establish a new library-comparison method for isomers distinction. The method firstly established a data library comprising MS/MS characteristic fragment, MS/MS profile, and retention time (R.T.) value. Through subsequent comparisons, 22 phytophenol isomers in D. styracifolium have been simultaneously distinguished under MS spectra negative model. The results suggested that: (1) there were four main types of isomers, i.e., positional isomers, functional group isomers, skeleton isomers, and hybridized isomers. (2) The hybridized isomers (e.g., luteoloside and astragalin) could be easily distinguished, while positional isomers (e.g., schaftoside and isoschaftoside) were difficultly distinguished from each other. (3) The R.T. value comparison played a key role for distinction of highly similar isomers, especially positional isomers. On the basis of above results and computational chemistry, it is concluded that, the new UHPLC-Q-orbitrap MS/MS-based library-comparison method can be capable for isomers distinction and thus has developed the UHPLC-Q-orbitrap MS/MS technology. The development will benefit many fields, including food, herbal medicine, and analysis chemistry. Particularly, the data of 22 phytophenol isomers can be directly cited for their isomersdistinction in future by other researchers.