Estrogens and congeners from spent hops (Humulus lupulus)

Estrogenicity-directed fractionation of a methanol extract of the strobiles of Humulus lupulus that had been extracted previously with supercritical CO2, known as "spent hops", led to the isolation and identification of 22 compounds including 12 prenylated chalcones (1-8, 10-13), five prenylflavanones (14-17), 4-hydroxybenzaldehyde (18), sitosterol-3-O-beta-glueopyranoside (19), humulmone (20), and coliumulmone (21). In addition, the prenylated chalcone xanthohumol C (9a) was obtained as a 6:1 mixture along with its 1",2"-dihydro derivative (9b). Three new chalcones (4, 11, 12) and four previously unreported constituents of hops (5, 6, 9b, 13) are reported. The structures of the new compounds were determined through a combination of spectrometric techniques including 1D and 2D NMR, HRESIMS, and ESIMS-MS. Full H-1 NMR spin system analyses were performed to characterize the higher-order glueopyranosyl, prenyl, and chalcone B-ring spectra of the isolates. The principle estrogen 8-prenyl-naringenin (15) from hops is an artifact formed along with its positional isomer 6-prenylnaringenin (16) through the spontaneous isomerization of the pro-estrogenic chalcone DMX (7).