ISOLATION AND CHARACTERIZATION OF TWO ISOHUMULONE ISOMERS

Isohumulones may be prepared by boiling humulone in a buffer solution of medium pH or by the methods of Howard and of Windisch et al., who use alkaline solutions. Medium pH is to be preferred as no humulinic acid is formed. The reaction product may be resolved by reversed-phase partition chromatography into two isomeric substances, one optically inactive and one dextrorotatory isohumulone with very similar properties. When purified humulone is used, small amounts of co- and ad-humulone are present and give rise to the corresponding iso-compounds. The same six isohumulones are present in beer. An isooctane extract of beer which is resolved into three fractions by countercurrent distribution thus gives five to six peaks when an efficient chromatographic procedure is used. No substance corresponding to the resin B of Windisch et al. has been observed in the isomerization mixture at any pH.