Chemical profiling of bioactive constituents in hop cones and pellets extracts by online comprehensive two-dimensional liquid chromatography with tandem mass spectrometry and direct infusion Fourier transform ion cyclotron resonance mass spectrometry

Humulus lupulus L. (hop) is highly interesting from a nutraceutical perspective. The hop phytocomplex contains a wide range of bioactive metabolites, and its characterization is challenging. To tackle such a task, for the first time we applied and compared a combined approach consisting of online comprehensive two-dimensional liquid chromatography with tandem mass spectrometry and direct infusion Fourier transform ion cyclotron mass spectrometry. A reversed phase × reversed phase approach with a shifted gradient in the second dimension ensured selectivity and two-dimensional space coverage. Hyphenation with an ion trap time-of-flight analyzer led to the identification of 83 compounds in 70 min, comprising a novel quercetin derivative and six unknown bitter acids. On the other hand, the direct infusion method was able to identify 40 analytes (except isomers) with high mass accuracy (≤ 0.1 ppm) in less than 1 min analysis time. The developed approach can be used in a complementary way, combining the separation capability and high informative spectra of two-dimensional liquid chromatography tandem mass spectrometry with the ultra-high mass accuracy of direct infusion, for potential compound discovery or the accurate profiling of bioactive compounds in different hop cultivars as well as for monitoring processing and storage of hop-based products.