Classification and biological activity of phytoestrogens: A review

Abstract

Phytoestrogens represent polyphenolic and non-steroid compounds that have a similar structure and biological activity as human estrogens. They are the plant secondary metabolites and widespread in over 300 various plant species. The phytoestrogens are divided into two main subgroups, isoflavonoids and lignans. The isoflavonoids are divided into isoflavones and coumestans. Isoflavones are most present in soybean and red clover. A great number of isoflavones has been identified in the plants in the form of non-active glycosides (daidzein and genistein) and in the form of 4'-methylated derivatives (formononetin and biochanin A). Coumestans can also be found in red clover and legumes, while lignans are most present in the flax seed. Coumestans have the most pronounced estrogenic effect of all phytoestrogens. The most famous representative of this subgroup of compounds is coumestrol. Lignans include matairesinol, secoisolariciresinol, lariciresinol, pinoresinol and their metabolites, enterodiol, enterolactone and equol. Numerous studies in animals and humans have shown that phytoestrogens can have protective effects in the estrogen-dependent conditions and estrogen-dependent diseases. It was also shown that the use of phytoestrogens can have a positive effect on insomnia and cognitive functions, i.e. neural disorders, such as Alzheimer's disease. They can express the antioxidant activity in two ways, as the scavengers of free radicals or by the formation of chelating complexes with metal ions. Free metal ions increase the amount of reactive oxygen species by reduction of hydrogen peroxide resulting in a very reactive hydroxyl radical.

Cicer arietinum L. Sprouts’ Influence on Mineralization of Saos-2 and Migration of MCF-7 Cells

“…Regardless of the positive effects of the C. arietinum sprouts observed in vitro, the in vivo effectiveness of isoflavonoids is regulated by their bioavailability, which depends on their form. It is known that isoflavone glycosides must be metabolized by the intestinal microflora to be transformed into bioavailable forms [ 45 ]. The efficacy of microbiological transformation depends, in turn, on the overall population and composition of the intestinal microbiota, especially in older subjects with poor intestinal colonization.…”

“…To avoid this disadvantage, the sprouts were hydrolyzed with β-glucosidase, which released the aglycones of formononetin and biochanin A’s methylated derivatives. Methylated derivatives are approximately three-times-better absorbed than unmethylated forms and are distributed in the plasma [ 45 ]. Further metabolism to genistein and daidzein to equol in the next step can occur, but the rate of biotransformation depends on many factors; future studies on the dependence of the isoflavonoid extract composition, plasma concentration and action must therefore be performed in vivo with many subjects.…”

Food Bioactive Compounds and Emerging Techniques for Their Extraction: Polyphenols as a Case Study

“…Lignans is a group of natural non-flavonoids phytoestrogens structurally characterized by the combination of two phenylpropanoid units connected at the β and β’ carbon atoms [ 47 ]. They have a wide occurrence in nature and the main sources of dietary lignans are whole-grain cereals, oilseeds, fruit, vegetables, and some beverages, such as tea, coffee, and wine [ 25 ].…”

Targeting Abdominal Obesity and Its Complications with Dietary Phytoestrogens

“…The term "phytoestrogen" was developed in 1926 (from the Greek words phyto-"plant"-and estrogen-"sex hormone") and refers to a functional, not chemical, classification of compounds. Phytoestrogens belong to polyphenols and, based on their chemical structure, are divided into two main groups: flavonoids (including isoflavones and coumestans) and non-flavonoids (including lignans and resorcinol derivates) [16].…”