Biosynthesis of bitter acids in hops -: A 13C-NMR and 2H-NMR study on the building blocks of humulone

The biosynthesis of humulone, an antibacterial bitter acid from hops, was studied by isotope-incorporation experiments using C-13-labelled glucose or (H2O)-H-2. C-13 enrichments, H-2 enrichments and (CC)-C-13-C-13 coupling patterns identify isovaleryl-CoA, malonyl-CoA and dimethylallyl pyrophosphate as precursors for humulone. Dimethylallyl pyrophosphate, which serves as a building block for the bitter acid, is generated via the deoxyxylulose pathway of terpenoid biosynthesis. The data confirm that a symmetrical intermediate is involved in humulone formation.