Hop (Humulus lupulus L.) Proanthocyanidins Characterized by Mass Spectrometry, Acid Catalysis, and Gel Permeation Chromatography

Proanthocyanidins extracted from hops (Humulus lupulus L. cv. Willamette) were subjected to Sephadex LH-20 column chromatography using a step gradient of methanol, water, and acetone. The resulting fractions were analyzed by acid catalysis, electrospray ionization and matrix-assisted laser desorptio...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2003-07, Vol.51 (14), p.4101-4110
Main Authors: Taylor, Alan W, Barofsky, Elizabeth, Kennedy, James A, Deinzer, Max L
Format: Article
Language:English
Subjects:
acetone
Anthocyanins - chemistry
Beers
Biological and medical sciences
Catalysis
catalytic activity
catechin
Catechin - analysis
Chromatography, Gel
desorption
epicatechin
epigallocatechin
Fermented food industries
Food industries
Fundamental and applied biological sciences. Psychology
gel permeation chromatography
hops
Humulus - chemistry
Humulus lupulus
Hydrogen-Ion Concentration
ionization
Mass Spectrometry
methanol
polymerization
polymers
Proanthocyanidins
Spectrometry, Mass, Electrospray Ionization
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Summary:Proanthocyanidins extracted from hops (Humulus lupulus L. cv. Willamette) were subjected to Sephadex LH-20 column chromatography using a step gradient of methanol, water, and acetone. The resulting fractions were analyzed by acid catalysis, electrospray ionization and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and gel permeation chromatography (GPC). The proanthocyanidins contained catechin and epicatechin as monomers and as terminal and extension units. Epigallocatechin was found as extension units. The mean degree of polymerization (mDP) of the crude proanthocyanidins was 7.8, but heptamers were the largest oligomers visible in mass spectra of the whole. In the last-eluted fraction (mDP = 22.2), polymers as large as 20-mers were detected by MALDI-TOF-MS, demonstrating the effectiveness of prior separation in improving MS detection. GPC data correlated well with acid catalysis results, confirming the presence of large polymers that were not detected by MS. Keywords: Proanthocyanidin; hops; Humulus lupulus; acid catalysis; gel permeation chromatography (GPC); electrospray ionization (ESI); matrix-assisted laser desorption/ionization (MALDI); time-of-flight (TOF); mass spectrometry (MS)
ISSN:0021-8561
1520-5118
DOI:10.1021/jf0340409