Tandem mass spectrometry for sequencing proanthocyanidins.
Proanthocyanidins (PAs) are a group of bioflavonoids consisting of oligomers based on catechin monomeric units. These polyphenolic compounds are widely distributed in higher plants and are an integral part of the human diet. A sensitive LC-tandem mass spectrometric (LC/ESI-MS(n)) method in the positive ion mode for sequencing these ubiquitous and highly beneficial antioxidants is described. The hydroxylation patterns and interflavanoid linkage for A- and B-type PAs were determined by fragment ions derived from a retro-Diels-Alder (RDA) fission, heterocyclic ring fission (HRF), a novel benzofuran-forming (BFF) fission described here for the first time, and a quinone methide (QM) fission. The subunit sequence of the PAs was determined by diagnostic ions derived from HRF/RDA fission, HRF/BFF fission, and RDA/HRF fission together with QM fission. A total of 26 PAs were reliably sequenced by the newly established tandem mass spectrometric protocol. It is shown that the protocol based on a combination of these different fragmentation patterns allows for uniquely identifying PA oligomers.
Li
Hui-Jing
HJ
Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA.
Deinzer
Max L
ML
D002853:Chromatography, Liquid / Q000379:methods; D008968:Molecular Conformation; D044945:Proanthocyanidins / Q000032:analysis*; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013997:Time Factors
D044945:Proanthocyanidins