IDENTIFICATION OF ISOFLAVONOIDS IN BEER

The isoflavonoids, genistein (4',5,7-trihydroxyisoflavone), biochanin A (5,7-dihydroxy-4'-methoxyisoflavone), daidzein (4',7-dihydroxyisofla vone), and formononetin (7-hydroxy-4'-methoxyisoflavone) are supposed to be health-promoting dietary factors of plant origin. They are parti cularly abundant in seeds and other parts of many plant species belong ing to Leguminosae. The most popular source of isoflavonoids in human diet is soy. Here, evidence is presented that isoflavonoids are regula rly found in beer. Diethyl ether extracts of beer were fractionated on thin-layer chromatography-silica, (straight phase) and rechromatograp hed using a reversed phase high-performance liquid chromatography octa decylsilica column. The fractions were analyzed by two recently develo ped radioimmunoassays, the first of them being specific for daidzein/f ormononetin and the second one specific for genistein/biochanin A. The immunoreactivity was found only in fractions with the mobility corres ponding to the positions of standards on control chromatograms. Additi onally, 26 samples of bottled beer were analyzed for isoflavonoid cont ent using the combination of reversed phase high-performance liquid ch romatography and radioimmunoassay. The sum of the four isoflavonoids r anged from 1.26 to 29 nmol/L in individual beers. Formononetin was the major isoflavonoid (0.19-14.99 nmol/L), whereas the concentration of daidzein was several times lower (0.08-2.5 nmol/L). Genistein and bioc hanin A concentrations were comparable, ranging from 0.169-6.74 nmol/L and from 0.820-4.84 nmol/L for genistein and biochanin A, respectivel y. It is concluded that beer contains significant amounts of biologica lly biologically active isoflavonoid phytoestrogens. (C) 1998 by Elsev ier Science Inc.