Conversion of deoxyhumulone into the hop α-acid humulone

In the final step of the biosynthesis of hop bitter acids an oxidation leads to the formation of α-acids. A method was set up to analyse the bitter acids in the presence of proteins, since proteins from a crude hop extract were found to interact with the phenolic bitter acids and interfere with the extraction and assay of these acids. After examination of the interaction of bovine serum albumin with hop bitter acids, concentration of the samples by lyophilization and subsequent analysis by HPLC were used to study the conversion of deoxyhumulone into humulone. Two types of oxidation were found to take place in vitro: a chemical reaction and a reaction catalysed by an unknown factor from hop protein extracts. The results of this study indicate that this factor, isolated from the glandular hairs of hop cones, is an enzyme that is involved in the biosynthesis of α-acids.