Capillary zone electrophoresis method for determination of bitter (alpha- and beta-) acids in hop (Humulus lupulus L.) cone extracts.

PURPOSE: Humulus lupulus (H. lupulus), more commonly known as hop, is a member of the Cannabaceae family with male and female flowers on separate plants. It is native in Europe including Lithuania, Asia and North America. Hop has been recognized as a medicinal plant for centuries, nevertheless different medicinal activities of hop are currently investigated and discovered. An important class of hop compounds is the hop acids, which are classified as alpha-acids and beta-acids. Different varieties of hops vary in amount and composition of hop acids. METHODS: Simple capillary zone electrophoresis method has been optimized and applied for the analysis of hop acids in hop cone extracts. RESULTS: With this method the analysis takes ca. 10 min. Repeatability for migration times and peak areas expressed as relative standard deviation were up to 0.21% and 5.96%, respectively. CONCLUSIONS: Comparative results of capillary zone electrophoretic analysis of extracts of different hop varieties and conductometric titration, as a standard method for determination of alpha-acids, are presented. Both methods provide consistent results, however capillary zone electrophoresis is capable of separating co- form of humulones from other forms.