Determination of the hop-derived phytoestrogen, 8-prenylnaringenin, in beer by gas chromatography/mass spectrometry

A method was developed to determine 8-prenylnaringenin, a novel hop-derived phytoestrogen, in beer. Matrix purification involved solid-phase extraction on octadecyl silica followed by liquid/liquid extraction on a ChemElut 1010 column connected to a Florisil adsorption/desorption cartridge. 8-Prenylnaringenin was eluted from the tandem columns using a 1:1 mixture of diethyl ether and ethyl acetate and subsequently determined as tris(trimethylsilyl) ether by GC/MS-SIM. The recovery of 8-prenylnaringenin in beer samples was between 61.1 +/- 6.6 and 82.2 +/- 8.8% for levels of 37 and 92.5 microg L(-1), respectively, and the detection limit was approximately 5 microg L(-1). Although most beers do not contain 8-prenylnaringenin in detectable quantities, the highest concentration found was 19.8 microg L(-1). The concentration of 8-prenylnaringenin in beers and, possibly, its absence depend on the selection of particular hop varieties, the hopping rate, or the type of hop product used in brewing. The efficiency of transfer of 8-prenylnaringenin from hops to beer is between 10 and 20%.