PRENYLFLAVONOIDS FROM HUMULUS-LUPULUS

Five flavonoids were isolated from the resin part of the female inflor escences of Humulus lupulus, together with four known hop flavonoids, i.e. xanthohumol, 2',4',6',4-tetrahydroxy-3'-C-prenylchalcone, isoxant hohumol and 6-prenylnaringenin. The new hop compounds were identified as 2',4',6',4-tetrahydroxy-3'-C-geranylchalcone, 5'-prenylxanthohumol, 6'',6''-dimethylpyrano (2'',3'': 3',4')-2',4-dihydroxy-6'-methoxychal cone, its hydrate and 8-prenylnaringenin; apart from 8-prenylnaringeni n, these are new flavonoids. Their mass fragmentation patterns were st udied by mass spectrometry using atmospheric pressure chemical ionizat ion in combination with collision-activated decomposition. Loss of the isoprenoid substituent in the positive ion mode and retro Diels-Alder fission in both the positive and negative ion modes provided useful i nformation on the substitution patterns of the A and B rings. Nine hop varieties were qualitatively and quantatively characterized by HPLC-m ass spectrometry. The flavonoid profiles of the samples examined were uniform and proved to be of little value in hop variety identification . Xanthohumol was the principal flavonoid in all samples (80-90% of th e total of flavonoids) and was accompanied by minor amounts of the oth er eight flavonoids in virtually all samples. Copyright (C) 1997 Elsev ier Science Ltd.