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Phytoestrogens are plant-derived xenoestrogens (see estrogen) not generated within the endocrine system but consumed by eating phytoestrogenic plants. Also called "dietary estrogens", they are a diverse group of naturally occurring nonsteroidal plant compounds that, because of their structural similarity with estradiol (17-β-estradiol), have the ability to cause estrogenic or/and antiestrogenic effects, by sitting in and blocking receptor sites against estrogen.〔Theresa L. Crenshaw and James P. Goldberg: Sexual Pharmacology.〕 Their name comes from the Greek ''phyto'' ("plant") and ''estrogen'', the hormone which gives fertility to female mammals. The word "estrus" - Greek οίστρος - means "sexual desire", and "gene" - Greek γόνο - is "to generate". It has been hypothesized that plants use phytoestrogens as part of their natural defence against the overpopulation of herbivore animals by controlling female fertility. The similarities, at molecular level, of estrogens and phytoestrogens allow them to mildly mimic and sometimes act as antagonists of estrogen.〔 Phytoestrogens were first observed in 1926,〔 but it was unknown if they could have any effect in human or animal metabolism. In the 1940s and early 1950s, it was noticed that some pastures of subterranean clover and red clover (phytoestrogen-rich plants) had adverse effects on the fecundity of grazing sheep.〔 Researchers are exploring the nutritional role of phytoestrogens in the regulation of cholesterol and the maintenance of proper bone density post-menopause. Evidence is accruing that phytoestrogens may have protective action against diverse health disorders, such as prostate, breast, bowel, and other cancers, cardiovascular disease, brain function disorders and osteoporosis,〔〔 Phytoestrogens cannot be considered nutrients, given that the lack of these in the diet does not produce any characteristic deficiency syndrome nor do they participate in any essential biological function.〔 Analytical methods are available to determine phytoestrogen content in plants and food. == Structure == Phytoestrogens mainly belong to a large group of substituted natural phenolic compounds: the coumestans, prenylflavonoids and isoflavones are three of the most active in estrogenic effects in this class. The best-researched are isoflavones, which are commonly found in soy and red clover. Lignans have also been identified as phytoestrogens, although they are not flavonoids.〔 Mycoestrogens have similar structures and effects, but are not components of plants; these are mold metabolites of ''Fusarium'', especially common on cereal grains, but also occurring elsewhere, e.g. on various forages. Although mycoestrogens are rarely taken into account in discussions about phytoestrogens, these are the compounds that initially generated the interest on the topic. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phytoestrogens」の詳細全文を読む スポンサード リンク
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