A dichotomy in the lipophilicity of natural estrogens, xenoestrogens, and phytoestrogens.

Using two independent analyses, it is demonstrated that natural (e.g., estradiol) and some xenoestrogens (e.g., methoxychlor metabolite) are characterized by a lipophilic region that is absent in nonestrogens as well as in phytoestrogens. It is suggested that this lipophilic region affects binding to specific receptors and may, in fact, differentiate harmful from beneficial estrogens.