Isoflavones estrogenic potency

In 1961, Bickoff proposed that methylation could be the mechanism by which the estrogenic potency of isoflavones is reduced. In addition, the different potency of genistein and daidzein could be due to the presence of the hydroxyl group of genistein [7],... 

The three major chemical types of phytoestrogens that have been identified are flavones, isoflavones, and coumestans. The estrogenic potency of these com pounds is variable. The flavones are weak estrogens. The methoxyflavone, tricin, is a constituent of alfalfa and weakly estrogenic in the mouse. 

The three main classes of phytoestrogens (and common food sources) are isoflavones (soybeans), lignans (cereals and oilseeds such as flaxseed), and coumestans (alfalfa sprouts). The biologic potency of phytoestrogens varies and is less than that of synthetic estrogen. 

As regards these and those previously reported, a hierarchy of estrogenic activity may be proposed, in which flavone 7, 4 -dihydroxylate has the lowest activity and coumestrol with its internal cyclation the highest, Fig. (6). Table 2 shows the relative potencies of different isoflavones and coumestrol in different models for evaluating estrogenic activity. 

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