K-Targeted Metabolomic Profiling and Generation of Knock-Out Extracts of Hops (Humulus lupulus L)

This study develops K-targeted metabolomic profiling as a new method for botanical standardization. The method combines selective enrichment of a metabolite, or a group of congeneric metabolites, from a complex extract by means of countercurrent separation (CCS), with exhaustive chemical characterization of the end-products, namely the isolated metabolites and the deprived extract. This two-pronged approach was applied to target the enrichment of isoxanthohumol (IX), xanthohumol (XH), 8-prenylnaringenin (8-PN), and 6-prenylnaringenin (6-PN) from hops. Highly orthogonal analytical techniques, UHPLC with UV detection and quantitative NMR (qNMR) were chosen for the metabolomic fingerprinting of each end-product and the quantitation of targeted metabolites. After two CCS steps, using HEMWat 0 and HterAcWat +3 or HEMWat -3, the purity of each targeted hops marker was determined by qNMR. The other fractions obtained by CCS were recombined, thus yielding an extract deprived of its specific markers, which was fully characterized by UHPLC-UV and qNMR. This knock-out extract can be regarded as a powerful pharmacological tool to study the biological impact of targeted metabolite within an extract.