Detection of estrogen active compounds in hops by planar yeast estrogen screen

Hops used in the brewing process of beer for flavoring are known to contain estrogen active compounds (EAC) and to be the source of EAC in beer. The recently developed planar yeast estrogen screen (pYES) with the substrate resorufin-β-d-galactopyranoside (RGP) successfully was applied for the detection of EAC in ethanolic extracts of hops pellet samples. The only pYES positive compound was identified as the hop flavanone prenylnaringenin (PN) by thin-layer chromatography-mass spectrometry. The heat-induced formation of estrogen active PN from the inactive hop flavonoid desmethylxanthohumol was confirmed by simulation of wort boiling, extraction of both the hops' remainder and the supernatant water, and subsequent investigation of the extracts by pYES. By means of the dose-response curve of PN of a hops' remainder extract, the estradiol equivalent concentration (EEQ) and thus the estradiol equivalent amount (EEA) of PN in the hops' remainder after simulation of the wort boiling was determined to 39 μg/L and 52 μg/kg, respectively.