Daidzein and genistein content of fruits and nuts

Dietary phytoestrogens such as the isoflavones daidzein and genistein are t hought to protect against chronic diseases that are common in Western socie ties, such as cancer, osteoporosis and ischemic heart disease. Irt addition , there are concerns regarding the deleterious effects of hormone-like comp ounds, especially with respect to the development of infants. However, ther e is little information regarding the phytoestrogen content of foods, and t herefore epidemiologic investigations of phytoestrogens are limited. As par t of a study quantifying the consumption of phytoestrogens, the objective o f this work was to assess the daidzein and genistein content of fruits and nuts commonly eaten in Europe. Eighty different fruits and nuts were sample d prepared for eating, and freeze-dried Daidzein and genistein were extract ed from the dried foods, and the two isoflavones were quantified after hydr olytic removal of any conjugated carbohydrate. Completeness of extraction a nd any procedural losses of the isoflavones were accounted for using synthe tic daidzin (7-O-glucosyl-4'-hydroxyisoflavone) and genistin (7-O-glucosyl- 4'5-dihydroxyisoflavone) as internal standards. Of the 80 foods assayed, 43 contained no detectable daidzein or genistein, at a limit of quantificatio n of 1 mu g/kg dry weight of food. Nine foods contained more than 100 mu g of the two isoflavones combined per kilogram wet weight, and 28 contained l ess than this amount. Currants and raisins were the richest sources of the isoflavones, containing 2,250 mu g and 1,840 mu g of the two isoflavones co mbined per kilogram of wet weight of food Although fruits and nuts are not as rich in isoflavone phytoestrogens as are soy and other legumes this is t he first documentation of levels of daidzein and genistein occurring in the se foods. (J. Nutr. Biochem. 11:326-331, 2000) (C) Elsevier Science Inc. 20 00. All rights reserved.