Abstract (eng)
In this study the first supercritical fluid based protocol for the identification and quantification of five characteristic polar reference substances in hops products was developed. One chalcone (xanthohumol), three flavanones (isoxanthohumol, 8-prenylnaringenin, 6-prenylnaringenin) and hulupinic acid, an oxidation product of hops bitter acids, were used as reference compounds.
Six mono hops dietary products were obtained from online pharmacies and extracted with EtOH 96% according to a published extraction protocol. A UPC² (Acquity UltraPerformance Convergence ChromatographyTM) method was developed for the five reference compounds using a mobile phase consisting of CO2 and isopropanol (IPA). Within 5 minutes all 5 reference substances could be baseline separated using a Viridis BEH 2-EP column (3.0 x 100 mm; 1.7 µm particle size).
All compounds were quantified in the six commercial products and the method was validated according to ICH guidelines. The optimized protocol and validation on UPC² achieved good results - also compared to other chromatographic methods like HPLC.
In addition, a second UPC² method was successfully established to separate and detect all compounds (from non-polar to polar) within a complex hops crude extract.
The last step was a scaling up of this method to SFC Prep-15 (preparative supercritical fluid chromatography) carried out with a Viridis BEH 2-EP column (10 x 250 mm; 5 µm particle size). However, separation and isolation of pure compounds were not satisfying on the SFC Prep-15 instrument due to the inherent instability of hops constituents.