Composition of the essential oils from leaves of various Humulus lupulus L. cultivars

Abstract

AbstractCultivars of hop, Humulus lupulus L., are of economic importance for breweries, since hop cones contain a resinous fraction, responsible for the bitter taste of beer, and a volatile fraction, which contributes to its flavour. Till now research on the presence of volatile compounds in the leaves of hop plants has not been reported.Dried leaves of ten cultivars were submitted to hydrodistillation, using the apparatus described in the European Pharmacopoeia. A trap of pentane was necessary to detect and to take up the oils, because hop leaves contain volatile compounds to a much lesser extent than hop cones (<0.05%).The oils were analysed by GC and GC–MS. Of the many components detected 36 were identified, among which were eleven alkanes. In all oil samples sesquiterpene hydrocarbons clearly predominated; α‐humulene (3‐23%) and β‐caryophyllene (5‐29%) were the main components. β‐Myrcene, one of the main components of the essential oils from the cones of the same cultivars, was found in the leaf oils in a concentration of 1% or less.