Isoflavones

Křížová L1Dadáková K2Kašparovská J3Kašparovský T4.

Molecules. 2019 Mar 19;24(6). pii: E1076. doi: 10.3390/molecules24061076.

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.

Conclusions Isoflavones are polyphenolic compounds that represent one of the most common categories of phytoestrogens. These secondary plant metabolities are structurally similar to 17β-estradiol and are found mainly in the Fabaceae family usually in a conjugated form. Before being metabolized, they are hydrolysed into aglycones by the microflora present in the human or animal digestive tract or by the enzymes of the gastrointestinal tract. Except for their role in the plant interaction with its environment, they also show numerous health benefits often connected with their estrogenic activity, for which they have been intensively studied for decades. On the other hand, they may also be considered endocrine disruptors with the potential to cause adverse effects on human or animal health either directly through their consumption in food/feed or indirectly through the contamination of the environment, mainly surface water. Furthermore, inconsistency in the results obtained from isoflavone studies performed on various subjects suggest that microflora involved in the metabolism of isoflavones plays a key role in their final effect on the target organism because it can convert the parent molecules into metabolites, such as equol, with altered (higher) estrogenic activity. Many studies focused on identification of bacteria capable to convert daidzein into equol with the aim to produce food supplements, while other studies focused on production of isoflavone/equol-enriched milk or dairy products through the manipulation of dairy diets and metabolic processes in the rumen. However, these manipulations lead to increased excretion of isoflavones into the environment with subsequent estrogenic contamination of surface water. Further studies in many areas of isoflavone research are needed to improve our understanding in this extremely complex field of study

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