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      Isoflavones

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          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.

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          Mechanisms of anabolic therapies for osteoporosis.

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            Deglycosylation by small intestinal epithelial cell beta-glucosidases is a critical step in the absorption and metabolism of dietary flavonoid glycosides in humans.

            Pharmacokinetic studies have shown that the small intestine is the major site of absorption for many flavonoid glucosides. Flavonoids are generally present as glycosylated forms in plants and foods, but there is increasing evidence that the forms reaching the systemic circulation are glucuronidated, sulphated and methylated derivatives. Hence, first-pass metabolism (small intestine-liver) appears to involve a critical deglycosylation step for which the mechanisms are not known. To explore the hypothesis that deglycosylation is a prerequisite to absorption and metabolism of dietary flavonoid glycosides, to identify the enzymes responsible, and relate their specificities with absorption kinetics. Flavonoid glycoside hydrolysing enzymes were isolated from samples of human small intestine and liver using chromatographic techniques. The proteins were characterised with respect to the cellular fraction with which they were associated, molecular weight, specificity for various substrates, and cross-reactions with antibodies. Cellular models were used to mimic the small intestine. Protein extracts from human jejunal mucosa were highly efficient in hydrolysing flavonoid glycosides, consistent with an enterocyte-mediated deglycosylation process. Considerable inter-individual variation was observed [e. g. range, mean and standard deviation for rate of hydrolysis of quercetin-3-glucoside (n = 10) were 6.7-456, 96, and 134 nmol min(-1) (mg protein)(-1), respectively]. Two beta-glucosidases with activity towards flavonoid glycosides were isolated from human small intestine mucosa: lactase-phlorizin hydrolase (LPH; localised to the apical membrane of small intestinal epithelial cells) and cytosolic beta-glucosidase (CBG), indicating a role of human LPH and CBG from small intestine in flavonoid absorption and metabolism. Hydrolysis of flavonoid glycosides was only detected in cultured cells exhibiting beta-glucosidase activity. The absorption of dietary flavonoid glycosides in humans involves a critical deglycosylation step that is mediated by epithelial beta-glucosidases (LPH and CBG). The significant variation in beta-glucosidase activity between individuals may be a factor determining variation in flavonoid bioavailability.
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              Impact of polyphenols and polyphenol-rich dietary sources on gut microbiota composition.

              Gut microbiota plays a key role in host physiology and metabolism. Indeed, the relevance of a well-balanced gut microbiota composition to an individual's health status is essential for the person's well-being. Currently, investigations are focused on analyzing the effects of pre- and probiotics as new therapeutic tools to counteract the disruption of intestinal bacterial balance occurring in several diseases. Polyphenols exert a wide range of beneficial health effects. However, although specific attention has been paid in recent years to the function of this "biological entity" in the metabolism of polyphenols, less is known about the modulatory capacity of these bioactive compounds on gut microbiota composition. This review provides an overview of the latest investigations carried out with pure polyphenols, extracts rich in polyphenols, and polyphenol-rich dietary sources (such as cocoa, tea, wine, soy products, and fruits) and critically discusses the consequences to gut microbiota composition which are produced.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                Molecules
                Molecules
                molecules
                Molecules
                MDPI
                1420-3049
                19 March 2019
                March 2019
                : 24
                : 6
                : 1076
                Affiliations
                Department of Biochemistry, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic; Ludmila.S@ 123456seznam.cz (L.K.); 147047@ 123456mail.muni.cz (K.D.); 20829@ 123456muni.cz (J.K.)
                Author notes
                [* ]Correspondence: tkasp@ 123456sci.muni.cz ; Tel.: +420-549-494-827
                Author information
                https://orcid.org/0000-0003-1616-1207
                Article
                molecules-24-01076
                10.3390/molecules24061076
                6470817
                30893792
                c4a33822-af68-4c37-b0ca-dbf567cc3075
                © 2019 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 08 February 2019
                : 01 March 2019
                Categories
                Review

                isoflavones,phytoestrogens,daidzein,genistein,glycitein,formononetin,biochanin a,equol

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