Quantification of co-, n-, and ad-lupulone in hop-based dietary supplements and phytopharmaceuticals and modulation of their contents by the extraction method.

Hop β-bitter acids (lupulones) are health-beneficial components of Humulus lupulus L. showing, for example, antidepressant-like effects in vitro. Despite of the widespread use of hops for medicinal purposes, the concentrations of lupulones in hop-based drugs have not been reported yet. The present study developed, validated, and applied a method with external calibration, which allows for the first time separate quantification of co-, n-, and ad-lupulone in hop-based drugs by UHPLC‒DAD. Concentrations between 'not detectable' and 2.7 mg/mL co-lupulone, 2.2 mg/mL nlupulone, or 0.7 mg/mL ad-lupulone were measured in nine different commercial dietary supplements and phytopharmaceuticals. Only one hop tincture contained sufficient lupulone to possibly exert potential antidepressant effects. Aiming for products with increased lupulone content, the extraction efficiency of different solvents was investigated. Complete extraction of lupulones from raw hops was achieved by organic solvents including methanol and ethanol, whereas aqueous mixtures resulted in low recovery. These results indicate that adapted extraction conditions may result in more effective hops products.