The mass spectral analysis of isolated hops A-type proanthocyanidins by electrospray ionization tandem mass spectrometry

✍ Scribed by Hui-Jing Li; Dr. Max L. Deinzer

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 399 KB
• Volume: 43
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1411

✦ Synopsis

Abstract

Comprehensive mass spectral fragmentation patterns have been established for sequencing chromatographically isolated A‐type proanthocyanidins (PAs) using electrospray ionization tandem mass spectrometry (ESI‐MS^n^) in the positive ion mode similar to those used for sequencing previously reported B‐type PAs. Sequence‐identifying fragmentations for A‐type PAs include heterocyclic ring fission (HRF), retro‐Diels–Alder (RDA) fission, benzofuran‐forming (BFF) fission, and quinone methide (QM) fission. There is commonality in fragmentation patterns between A‐type and B‐type PAs, but distinguishing features in the mass spectral patterns between the two classes include 2‐Da mass differences in the pseudo molecular ions, the propensity for the A‐type PAs to undergo QM fissions and yield bis‐quinoid ions as opposed to mono‐quinoid ions in the upper unit of the sequence, and the reluctance of A‐type linkages to undergo RDA, BFF, and BFF/H~2~O fissions from the upper unit. The positions of one or more A‐type (C2 → O → C7′) ether linkages have been located in sequences of PAs ranging in chain lengths of two to five monomer units using ESI‐MS^n^ data. Using the fragmentation information from ESI‐MS^n^ experiments, a total of 17 PAs were structurally sequenced by systematic real time ESI‐MS^n^. Among them ten A‐type and six B‐type hop PAs are reported here for the first time. Copyright © 2008 John Wiley & Sons, Ltd.