Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry

Abstract

Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS(3) experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice).

Dendropanax morbifera Leaf Polyphenolic Compounds: Optimal Extraction Using the Response Surface Method and Their Protective Effects against Alcohol-Induced Liver Damage

“…The MS analysis in the cation mode produced a [M + H] + of 355, which was determined to be an isomer of caffeic quinic acid, where caffeic acid is bonded to the hydroxyl group of quinic acid, based on identical molecular ions; the molecular ion peak at m/z 163.1 after the removal of H 2 O from caffeic acid; the peak at m/z 135.1 after the removal of CO from the peak at m/z 163.03. This pattern of molecular ion peaks agreed with the results of a previous study [35]. The peak at 19.9 min retention time exhibited maximum UV absorption peaks at 206, 256, and 353 nm, with molecular ion values of [M + H] + and [M + Na] at m/z 611.15 and m/z 633.14, respectively.…”

Chlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity

“…Matsui et al successfully ngerprinted several CQA, FQA and diCQA regio-isomers using two different collision energies in positive ion mode (15 and 30 eV) and three different collision energies in negative ion mode (20, 40 and 60 eV), 128 but this is too cumbersome for routine use. Similar limitations are apparent in the methods reported by Lin and Harnly, 129,130 and Willems et al 131 Ion-trap-MS has its limitations, most apparent where there is an aliphatic dicarboxylic acid substituent (e.g. succinic acid) because the fragmentations can be driven also by the distal carboxyl of that substituent in addition to the quinic acid carboxyl.…”

Recent advances in extraction and analysis procedures of natural chlorogenic acids

“…This is why the ESI ionization source, the most sensitive of all atmospheric pressure ionisation sources, typically operates in the negative mode. The correctness of this statement is confirmed by the data comparing the CQAs ionization efficiency of ESI and APCI in both positive and negative mode (Lai et al 2007;Shen et al 2010;Willems et al 2016). For most MS applications for CQAs analysis (see Table 1), the tandem MS worked under relatively high collision energy conditions (to 47 eV) to generate second order mass spectra.…”