Structural Study of Phenolic Acids by Triple Quadrupole Mass Spectrometry with Electrospray Ionization in Negative Mode and H/D Isotopic Exchange

Abstract

This work reports the theoretical and experimental study of fragmentation reactions in the gas phase of five phenolic acids using triple quadrupole mass spectrometry by electrospray ionization in negative ionic mode, as well as the isotope exchange experiments. MS/MS spectra were analyzed to suggest the fragmentation mechanisms, while theoretical calculations at the theory level B3LYP/6-311+G** were performed to expose the proposed mechanisms viability for this class of compounds. As expected, compounds with aromatic methoxy substitution presented •CH 3 radical elimination as the principal fragmentation pathway, forming dystonic ions. Compounds without methoxy substituents dissociate with higher energies losing the CO 2 , CO and H 2 O. The isotopic marking experiments indicated the exchange of hydrogens by deuterases in the hydroxyl protons, which corroborates with the proposed mechanisms.

Characterization and profiling of polyphenolics of Brassica microgreens by LC-HRMS/MS and the effect under LED light

“…Compounds 1, 2 and 3 were identified as p-, m-and o-coumaric acid, respectively, with the same deprotonated molecular ion [M-H] − of m/z 163.0401 and the major fragment ion at m/z 119.0501 (Table 1). The main fragment ion of caffeic acid 6 was m/z 135.0451 (neutral loss of CO 2 , 44 amu, from [M-H] − ) Sinosaki et al, 2020). One study identified the presence of ferulic acid 5 in PC microgreens, although this was not seen in the current study which could imply that under the current combined lighting and photon flux the accumulation of 5 was inhibited (Kyriacou et al, 2020).…”

Thinned Nectarines, an Agro-Food Waste with Antidiabetic Potential: HPLC-HESI-MS/MS Phenolic Characterization and In Vitro Evaluation of Their Beneficial Activities

“…Compound 14 showed a [M-H] − ion at m / z 179 and was identified as caffeic acid. According to the literature data, the base peak ion at m / z 135 [M-H-CO 2 ] − and the fragment ions at m / z 161 [M-H-H 2 O] − and m / z 151 [M-H-CO] − highlighted the presence of a carboxylic acid and a phenolic group [ 35 ]. Two feruloylquinic acid isomers (compounds 15 and 27) were putatively identified.…”

“…The fragment ions at m / z 145 [M-H-H 2 O] − , m / z 135 [M-H-CO] − and m / z 93 [M-H-CO 2 -C 2 H 2 ] − suggested the presence of a phenolic group and the hydroxycinnamic acid moiety. According to the mass fragmentation pattern, compound 29 was annotated as p-coumaric acid [ 35 ]. Compound 34 displayed a [M-H] − ion at m / z 193 and a base peak ion at m / z 149 [M-H-CO 2 ] − .…”

“…The base peak ion and the fragment ions at m / z 178 [M-H-CH 3 ] − , m / z 160 [M-H-CH 3 -H 2 O] − and m / z 134 [M-H-CH 3 -CO 2 ] − indicated the presence of a free carboxylic acid and a methyl group. Based on the literature data, compound 34 was identified as ferulic acid [ 35 ]. Two dicaffeoylquinic acid isomers (compounds 42 and 46) were putatively identified and gave a [M-H] − ion at m / z 515.…”

Feature-Based Molecular Network-Guided Dereplication of Natural Bioactive Products from Leaves of Stryphnodendron pulcherrimum (Willd.) Hochr

“…Group 1 includes conjugates of gallic acid with sugars and small organic acids ( Figure 4 ). Fragmentation patterns of these compounds are characterized by the ions of m / z 169 (gallate) and 125 (3,4,5-trihydroxybenzene, ion derived from the decarboxylation of the gallate) [ 50 , 51 ]. If a sugar unit is present, common losses of H 2 O and consecutive losses of C 2 H 4 O 2 units from the residual hexose and the heterolytic cleavage of the sugar are observed [ 52 ].…”