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DOI: 10.1055/a-1130-0590
Quantitative Analysis of Prenylated Constituents in Commercial Hops Samples Using Ultrahigh-Performance Supercritical Fluid Chromatography[ # ]


Abstract
The importance of hops (the flowers of Humulus lupulus) as food and an herbal remedy is reflected by a large number of analytical methods published. However, supercritical fluid chromatography, a highly efficient, rapid, and “green” separation technique, has not been considered for hops samples so far. This prompted us to establish the first supercritical fluid chromatography-based protocol for the separation, identification, and quantitation of five prenylated constituents of hops. Hulupinic acid (
1), a prominent oxidation product of hop acids, three flavanones, i.e., 8-prenylnaringenin (
2), 6-prenylnaringenin (
3), and isoxanthohumol (
4), as well as the chalcone xanthohumol (
5) could be baseline separated in less than 5 minutes using a Viridis BEH 2-EP column (3.0 × 100 mm; 1.7 µm particle size) and a mobile phase consisting of CO2 and isopropanol. Good results regarding selectivity, accuracy (recovery rates: 85.0 – 113.1%), precision (intra-day ≤ 2.1%, inter-day ≤ 3.5%), and linearity (R2 ≥ 0.99) were obtained for both photodiode array and mass detection. The lowest detection limit at 220 nm was at 0.1 µg/mL (
1, 3, and
4), with mass detection even at 0.001 µg/mL (
4). As an application example of the validated method, the five hops constituents were quantified in three dietary supplements, one herbal medicinal product, and two batches of hop flowers (Lupuli flos). In most samples analyzed, the major component was
5 (0.01 – 1.02%), whereas the major component in Lupuli flos samples was compound
1 (0.12 – 0.21%). This protocol offers a fast and environmentally friendly alternative to liquid chromatography for the quality control of hops.
Key words
supercritical fluid chromatography - ultra-performance convergence chromatography - QDa, hops - Humulus lupulus - Cannabaceae# Dedicated to Professor Dr. Wolfgang Kubelka on the occasion of his 85th birthday.
Supporting Information
- Supporting Information
An overview on selected hops samples for the quantitation of compounds 1 – 5, chromatograms (UPC2-PDA) showing the method development and optimization of the make-up solvent as well as the six hops samples (Prod1–6) with optimized parameters are available as Supporting Information.
Publication History
Received: 15 January 2020
Accepted: 27 February 2020
Article published online:
17 March 2020
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