Abstract
Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.
Highlights
Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens
Their occurrence was first reported in the 1940s in connection with the “clover disease” [2], which appeared in Australia in sheep grazing subterranean clover (Trifolium subterraneum)
Tucker et al [52] or Njåstad et al [47] assume from the results of experiments with heifers and dairy cows that the main equol excretion route is via feces. These results indicate that there are substantial differences in the isoflavone metabolism between sheep and cattle
Summary
Phytoestrogensare arenaturally naturallyoccurring occurringnonsteroidal nonsteroidalphenolic phenolicplant plantcompounds compoundsand andcan canbebe divided into two main groups: flavonoids and non-flavonoids [19]. Flavonoids include isoflavones, divided into two main groups: flavonoids and non-flavonoids [19]. (5,7-dihydroxy-4′-methoxyisoflavone), and formononetin (7-hydroxy-4 ́-methoxyisoflavone) belong to isoflavone phytoestrogens. Point point out, equol is not a phytoestrogen, as it is not a natural plant compound. Solely metabolic product out, equol is is not a phytoestrogen, asas it it is is not a natural plant compound. It It is is solely a ametabolic product of intestinal bacteria. A source formononetin and daidzein, genistein, and glycitein and red clover asas a source ofof formononetin and biochanin A. Isoflavones may occur aglycons or as glycosides (Table 1). The structure of of isoflavones and their glycosides [24,25]
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