Fragmentation characteristics of hydroxycinnamic acids in ESI‐MSⁿ by density functional theory

Abstract

This work aims to analyze the electrospray ionization multistage mass spectrometry (ESI-MS ) fragmentation characteristics of hydroxycinnamic acids (HCAs) in negative ion mode. The geometric parameters, energies, natural bond orbitals and frontier orbitals of fragments were calculated by density functional theory (DFT) to investigate mass spectral fragmentation mechanisms. The results showed that proton transfer always occurred during fragmentation of HCAs; their quasi-molecular ions ([M - H] ) existed in more than one form and were mainly with the lowest energy. The fragmentation characteristics included the followings: (1) according to the different substitution position of phenolic hydroxyl group, the ring contraction reaction by CO elimination from benzene was in an increasingly difficult order: m-phenolic hydroxyl > p-phenolic hydroxyl > o-phenolic hydroxyl; and (2) ortho effect always occurred in o-dihydroxycinnamic acids (o-diHCAs), i.e. one phenolic hydroxyl group offered H , which combined with the other one to lose H O. In addition, there was a nucleophilic reaction during ring contraction in diHCAs that oxygen atom attacked the carbon atom binding with the other phenolic hydroxyl to lose CO . The fragmentation characteristics and mechanism of HCAs could be used for analysis and identification of such compounds quickly and effectively, and as reference for structural analogues by ESI-MS. Copyright © 2017 John Wiley & Sons, Ltd.

Mass Spectrometric Behavior and Molecular Mechanisms of Fermented Deoxyanthocyanidins to Alleviate Ulcerative Colitis Based on Network Pharmacology

“…In MS2, the possible structures of unknown anthocyanin metabolites may be deduced from HDX-MS experiments by comparing the fragmented mechanisms of known anthocyanin analogs [ 34 ]. Quantum chemistry can facilitate the interpretation, prediction, and analysis of MS data, particularly those obtained by MS/MS [ 35 , 36 ]. Using the tandem mass spectra of nondeuterated and deuterated vinylphenol-deoxyanthocyanins, we proposed two potential fragmentation pathways and calculated the optimized configurations, vibrational characteristics, IRCs, and relative energies of the transition states of these molecules using the DFT programme of Gaussian software.…”