Abstract: Accumulated structure-activity data on environmental estrogens has focused on several structural sub-categories within this general family of chemical agents. Of these compounds, the most extensively studied include phytoestrogens, macrolactones, alkylphenols and arylphenols. For phytoestrogens, binding to the estrogen receptor (ER) is observed for the flavone and isoflavone nucleus particularly when the stilbene-like core is appropriately functionalized with hydroxylation at the 4' and/or 7 positions. Simple alkyl phenols behave as weak estrogens when substituted at the para position with a branched aliphatic group such as found in p-octyl and p-nonyl phenol. In the case of polychlorinated biphenyls (PCBs), quantitative structure-activity studies (QSAR) indicate that the electron donating properties of the hydroxyl moiety and the aromatic component correlate highly with affinity to the ER. Further studies have shown that the phenolic ring of PCBs favor orientation over the estradiol D-ring with the hydroxyl group of the PCB in close proximity to the 17-hydroxyl of estradiol while maximizing the hydrophobic overlap in the central regions. Structure-activity studies on diphenylethanes, such as dichlorodiphenyltrichloroethane (DDT), demonstrate the significance of the substituents present on both the aryl rings and the side-chain. Other structural classifications include polyhalogenated carbocyles.

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