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

• Published in: Journal of agricultural and food chemistry Vol. 51; no. 14; pp. 4101 - 4110
• Main Authors: Taylor, Alan W, Barofsky, Elizabeth, Kennedy, James A, Deinzer, Max L
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.07.2003
• 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; Hop; Acid catalysis; Matrix assisted laser desorption ionization; Electrospray; Gel permeation chromatography; matrix-assisted laser desorption/ionization (MALDI); Characterization; gel permeation chromatography (GPC); Ionization; Humulus lupulus; electrospray ionization (ESI); Isolation; time-of-flight (TOF); Proanthocyanidin; hops; Mass spectrometry; mass spectrometry (MS)
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0340409

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)