Disambiguation of Isomeric Procyanidins with Cyclic B-Type and Non-cyclic A-Type Structures from Wine and Peanut Skin with HPLC-HDX-HRMS/MS

Abstract

Hydrogen/deuterium exchange coupled with high-resolution mass spectrometry was successfully applied for the identification of A-type tetrameric, pentameric, and hexameric procyanidins in peanut skin. This extended a previous study on isomeric cyclic B-type unconventional tetramer, pentamer, and hexamer procyanidins found in wine and cranberries. Not only had the method successfully identified the procyanidins with a single A-linkage (e.g., tetrameric m/z 1153.2608) by means of distinguishing them from their isomeric cyclic B-type analogues, but this method also worked for procyanidins with two or more A-linkages (such as the tetrameric m/z 1151.2452). As a further consequence, B-type cyclic pentamers and hexamers in wine have been elucidated with hydrogen/deuterium exchange (HDX) for the first time. Graphical Abstract ᅟ.

Relative abundances of novel cyclic prodelphinidins in wine depending on the grape variety

“…As previously seen by Longo et al here too, the c‐analogs appear to retain those features that distinguished them from their linear analogs, namely (a) the anticipated retention times and (b) the lower number of peaks (even just one). It was already reported that the increased polarity, a lower fragmentation probability (along with all the differences in the fragmentation patterns) and fewer peaks (usually only a main one with much smaller traces at higher retention times) are features distinguishing the cyclic from their linear (a‐ or l‐) counterparts.…”

“…The presence and distribution of cyclic B‐type proanthocyanidins containing (epi)gallocatechins (ie, prodelphinidins) in red and white wines have been demonstrated for the first time. Previous evidences of the relation between these cyclic oligomers and other factors (eg, winemaking procedures) were already shown for procyanidins . Overall, these two classes (cyclic B‐type procyanidins and cyclic B‐type prodelphinidins) showed similar behaviors under many respects: (1) the retention times were anticipated with respect to their linear analogs; (2) they showed much fewer HPLC peaks with respect to their linear analogs, indicating the presence of just one main regio‐ and stereoisomer; (3) the MS/MS spectra showed much less fragmentation with respect to their linear analogs (higher pseudo‐molecular ion intensity) at 15‐eV collision energy.…”

“…The HPLC‐HRMS/MS method applied was adapted from published reports . The HPLC‐HRMS system used consisted of a Q Exactive HRMS instrument (Thermo Fisher Scientific, Waltham, MA, USA) coupled to an Agilent 1260 HPLC (Agilent Technologies Santa Clara, CA, USA) with a 16 channel DAD detector.…”

“…In fact, the H/D replacement indicated that the main C 60 H 48 O 24 compound observed was of B‐type (Figure C), thus confirming the previous observations . The method allowed to identify correctly also the isomeric non cyclic A‐type procyanidins in a peanut skin extract …”

“…9,10 The method allowed to identify correctly also the isomeric non cyclic A-type procyanidins in a peanut skin extract. 12 Furthermore, the distribution of these species (cyclic tetrameric, pentameric, and hexameric procyanidins-CTP, CPP, and CHP, respectively) in many wines obtained from different grape varieties was investigated, showing that their proportions over the total amount of procyanidins (by number of monomer units) was related to the specific grape variety used for the winemaking procedure. 13 However, in the cited work, only the flavan-3-ols constituent (+)-catechin and (−)-epicatechin monomer units were addressed.…”