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 extractio n on octadecyl silica followed by liquid/liquid extraction on a ChemElut 10 10 column connected to a Florisil adsorption/desorption cartridge. 8-Prenyl naringenin was eluted from the tandem columns using a 1:1 mixture of diethy l ether and ethyl acetate and subsequently determined as tris(trimethylsily l) ether by GC/MS-SIM. The recovery of 8-prenylnaringenin in beer samples w as between 61.1 +/- 6.6 and 82.2 +/- 8.8% for levels of 37 and 92.5 mu g L- 1, respectively, and the detection limit was similar to 5 mu g L-1. Althoug h most beers do not contain 8-prenylnaringenin in detectable quantities, th e highest concentration found was 19.8 mu g L-1. The concentration of 8-pre nylnaringenin in beers and, possibly, its absence depend on the selection o f particular hop varieties, the hopping rate, or the type of hop product us ed in brewing. The efficiency of transfer of 8-prenylnaringenin from hops t o beer is between 10 and 20%.