Biosynthetic experiments with tall plants under field conditions. 18O2 incorporation into humulone from Humulus lupulus.

Five segments of a large hop plant (Humulus lupulus var. Hallertauer Magnum) carrying several cones were enclosed in sealed glass vessels that were gassed with (18)O(2). After 14 days, the segments were harvested and humulone and cohumulone were analysed by NMR spectroscopy and mass spectroscopy. The oxygen atoms in position 6 of humulone and cohumulone showed 9% (18)O enrichment, respectively. It follows that the C-6 hydroxy groups were introduced by oxygenase catalysis.