Phytoestrogens are natural compounds found in various plant species and they have the ability to bind to the estrogenic receptors, exerting agonist and/or antagonist effects. The main classes of phytoestrogens are isoflavones, lignans, and coumestranes. Isoflavones are plant bioactive nonsteroidal polyphenolic metabolites with antioxidant properties. They have a very close structure with 17β-estradiol and possess estrogenic/antiestrogenic effects. The main dietary source of isoflavones is soy (Glycine max L.). Other legumes, such as red clover (Trifolium pratense L.), alfalfa (Medicago sativa L.), and Genista species, have important content in isoflavones, showing nutritional or phytotherapeutic interest. In plants, isoflavones can be found mainly as non-active glycosides which are converted after ingestion, in the corresponding aglycones (e.g., genistein, daidzein) that have pharmacological activity. Many studies have demonstrated the benefits of dietary isoflavones in menopause and multiple chronic pathologies, including cardiovascular diseases, osteoporosis, and hormonal cancers. Dietary intake of isoflavones is widespread, mainly due to the consumption of soybean products. Analytical methods applied for the quantification of isoflavones allow both assessment of dietary intake of isoflavones and highlighting natural sources with phytotherapeutic potential. Health benefits of isoflavones justify the interest for this class of functional food; therefore, further clinical and epidemiological studies are required.
Part of the book: Superfood and Functional Food