Improved Analysis of Isomeric Polyphenol Dimers Using the 4th Dimension of Trapped Ion Mobility Spectrometry-Mass Spectrometry.

Dehydrodicatechins resulting from (epi)catechin oxidation have been investigated in different foods and natural products, but they still offer some analytical challenges. The purpose of this research is to develop a method using ultra-high performance liquid chromatography coupled with trapped ion mobility spectrometry and tandem mass spectrometry (UHPLC-ESI-TIMS-QTOF-MS/MS) to improve the characterization of dehydrodicatechins from model solutions (oxidation dimers of (+)-catechin and/or (-)-epicatechin). Approximately 30 dehydrodicatechins were detected in the model solutions, including dehydrodicatechins B with and -interflavanic configurations and dehydrodicatechins A with -configuration. A total of 11 dehydrodicatechins B, based on (-)-epicatechin, (+)-catechin, or both, were tentatively identified in a grape seed extract. All of them were of -configuration, except for one compound that was of -configuration. TIMS allowed the mobility separation of chromatographically coeluted isomers including dehydrodicatechins and procyanidins with similar MS/MS fragmentation patterns that would hardly be distinguished by LC-MS/MS alone, which demonstrates the superiority of TIMS added to LC-MS/MS for these kinds of compounds. To the best of our knowledge, this is the first time that ion mobility spectrometry (IMS) was applied to the analysis of dehydrodicatechins. This method can be adapted for other natural products.