Hop (Humulus lupulus L.) Essential Oils and Xanthohumol Derived from Extraction Process Using Solvents of Different Polarity

This study evaluates the content of essential oils (EOs) and prenylated flavonoid Xanthohumol (XN) in extracts of Slovenian hops, cultivar Aurora, obtained by using fluids of different polarity. It is a continuation of our previous work, investigating the extraction of bitter acids from hops. Extraction was conducted semi-continuously, using sub- and supercritical fluids of different polarity, i.e., carbon dioxide (CO2) and propane as non-polar and dimethyl ether (DME) as the polar solvent. The experiments explored a temperature range between 20 degrees C and 80 degrees C and pressures ranging from 50 bar to 150 bar. The content of XN in extracts was analysed using high-performance liquid chromatography and experiments demonstrated the largest concentration of XN was obtained using DME. In order to analyse the EO components in extracts, connected with a distinct odour, the steam distillation of extracts was performed and GC analysis was employed. Hop oil derived from CO2 extracts at specific conditions, had the highest relative concentration of linalool, beta-caryophyllene and alpha-humulene, and oil derived from propane extracts had the highest content of all other five selected components (myrcene, geraniol, farnesene, alpha-selinene and delta-cadinene). The relative content of the investigated EO components in DME extracts was similar to that in propane extracts.

Automated summary

This study evaluates the content of essential oils and prenylated flavonoid Xanthohumol in extracts of Slovenian hops, and compares the extraction efficiency using fluids of different polarity. The results show that dimethyl ether is the most effective solvent for extracting Xanthohumol, while the content of essential oils in propane extracts is similar to that in dimethyl ether extracts.