Daidzein and genistein contents of vegetables

Food samples (n 114) were prepared from vegetables commonly eaten in Europe . The glycosidic forms of the phyto-oestrogens daidzein and genistein were extracted from the dried foods into aqueous methanol. The isoflavones were quantified by GC-MS after hydrolytic removal of any conjugated carbohydrate . Completeness of extraction and any procedural losses of the isoflavones w ere accounted for using synthetic daidzin (7-O-glucosyl-4 ' -hydroxyisoflav one) and genistin (7-O-glucosyl-4 '5-dihydroxyisoflavone) as internal stand ards. Of the 114 foods assayed, at a limit of quantification of 0.1 mug/kg dry weight, forty-eight contained no detectable daidzein or genistein, fort y-one contained less than 100 mug/kg of the two isoflavones combined and th e remaining twenty-five contained more than this amount. Soyabean products contained between 470 and 1420 mg (average of 960 mg) daidzein and genistei n combined per kg wet weight of food, and legumes contained between 20 and 5750 mug/kg wet weight of food, with an average of 620 mug/kg. Cooking by b oiling in water caused a decrease in the daidzein and genistein content of food in twenty-four of twenty-eight foods. The extent of the decrease was v ariable and warrants further investigation. The present paper comprises the first comprehensive description of the content of daidzein and genistein i n vegetables.