Humulone (Hum)

Humulone is a bitter-tasting chemical compound found in the resin of mature hops (Humulus lupulus). Humulone is a prevalent member of the class of compounds known as alpha acids, which collectively give beer its characteristic bitter flavor. Humulone can be synthesized by the acylation of 1,2,3,5-benzenetetrol with isovaleryl chloride to give 2,3,4,6-tetrahydroxyisovalerophenone. This step is followed by prenylation with 1-bromo-3-methyl-2-butene to give humulone. The biosynthesis of humulone in Humulus lupulus starts with an isovaleryl-CoA unit and 3 malonyl-CoA units catalyzed by phlorovalerophenone synthase. This conversion yields the benzenoid 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one. Dimethylallyl pyrophosphate is then obtained from the deoxyxylulose pathway, where prenylation of the benzenoid occurs, yielding humulone.