Metabolomic fingerprinting, targeted xanthohumol quantification and network-based pathway analysis of hydroponically cultivated Humulus lupulus

Hop cones (Humulus lupulus) are highly valued, both commercially and therapeutically, due to their diverse array of bioactive secondary metabolites. However, relatively few studies have characterized the phytochemical profile of hops grown in controlled environments. This study investigated the phytochemical profile of the bioactive secondary metabolites in hydroponically cultivated Humulus lupulus. Hop seeds were germinated and cultivated using a deep-water culture (DWC) hydroponic system under controlled environmental conditions. The roots and shoots were harvested separately and extracted using different solvents. The total phenolic (TPC) and flavonoid (TFC) assays were performed. The complete metabolic profiling of the Humulus lupulus plant cultivated under controlled environmental conditions was studied using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). The signature compound of hops, i.e., xanthohumol, was quantified using ultra-performance liquid chromatography (UPLC). The metabolomics data were further studied for network-based pathway analysis. The results showed that methanol was the most effective solvent for extracting compounds from hop roots, yielding a TFC of 0.272 mg QE/mg hop extract and a TPC of 0.057 mg GAE/mg hop extract. The hydroponic cultivation resulted in plants enriched in fatty acids, phenolics, flavonoids, and terpenoids, as analyzed using LC-MS and GC-MS. The concentration of xanthohumol in the hydroponically grown Humulus lupulus was determined to be 21.82 µg mL−1. The network-based analysis revealed a highly interconnected metabolic network, in which lipid metabolism played a key role in coordinating biochemical pathways within the hydroponics system. These findings demonstrate that controlled growth conditions significantly shape the metabolic composition of Humulus lupulus and enable effective quantification of xanthohumol in a hydroponics system. These findings also establish a foundation for future investigation on optimizing hydroponic nutrient formulations to enhance xanthohumol yields for industrial-scale applications.