Characterization of Humulus lupulus glycosides with porous graphitic carbon and sequential high performance liquid chromatography quadrupole time-of-flight mass spectrometry and high performance liquid chromatography fractionation
Andrew J Caffrey1, Scott Lafontaine2, Jeff Dailey3
1Department of Viticulture and Enology, University of California, Davis CA, 95616, United States; Food Safety and Measurement Facility, University of California, Davis CA, 95616, United States.
Abstract:
Monoterpenes contribute to the characteristic aroma of several hop varieties and may occur as nonvolatile glycosides. Upon hydrolysis, the volatile terpenes are released from the glycoside precursors. Little is known, however, about the glycoside composition of hops. Seven pentose-hexose monoterpene alcohol glycosides from dried Humulus lupulus L. cv. Citra cones were isolated using high performance liquid chromatography separation and fractionation on a reverse phase phenyl-hexyl column. Further evaluation of each isolated fraction through HPLC qTOF MS with porous graphitic carbon (PGC) showed that the seven isolated monoterpenyl glycoside fractions could be further resolved into 20 isomers. Isolation on phenyl-hexyl followed by separation on PGC was needed to distinguish each isomer present. Additionally, the hop cones were screened for potential aroma glycosides. Using the PGC column combined with a database of over 900 potential glycosides, the identification of 21 additional monoterpene-polyol, norisoprenoid, volatile phenol, and aliphatic alcohol glycosides is reported.
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