Receptor binding and transactivation activities of red clover isoflavones and their metabolites

Department of Biotechnology, University of Natural Resources and Applied Life Sciences, Vienna, Austria.
The Journal of Steroid Biochemistry and Molecular Biology (Impact Factor: 3.63). 10/2008; 112(1-3):87-94. DOI: 10.1016/j.jsbmb.2008.08.007
Source: PubMed


Red clover extracts contain a variety of isoflavones, which have affinity toward estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta), androgen receptor (AR), and progesterone receptor (PR). Upon ingestion, they undergo various metabolic transformations. For a complete evaluation of red clover extracts and possible health benefits, the resulting metabolites should also be investigated. Biochanin A, formononetin, genistein, daidzein, dihydrobiochanin A, dihydroformononetin, dihydrogenistein, dihydrodaidzein, 3'-hydroxygenistein, 6-hydroxydaidzein, 6-hydroxydesmethylangolensin, equol, O-desmethylangolensin, angolensin, and p-ethylphenol were tested for their transactivation potential toward ERalpha, AR, and PR in yeast. Competitive binding assays with radiolabeled 17beta-estradiol, 17alpha-methyltrienolone or progesterone assessed binding to the respective ERalpha and ERbeta, AR, and PR. The compounds showed only weak binding affinity to AR and PR, with IC(50) values being greater (i.e., lesser affinity) than 10(-5)M for the respective receptor. So far, beneficial health effects have been attributed to the production of equol. We propose that other metabolites can also contribute to these effects. However, more detailed information for the formation of these metabolites in humans and for bioavailability data are required to confirm our assumptions.

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    • "The present study, confirms the presence of these compounds in the serum of study subjects. Due to the instability of the reference compounds [44], it was not possible to quantify hydroxylated serum metabolites such as 3′-hydroxygenistein, 6-hydroxydaidzein, and 6-hydroxy-O-desmethylangolensin. The primary metabolic reaction after RCI consumption is the demethylation of the methoxy group at the 4′-position, yielding genistein and daidzein [42] [45]. "
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    ABSTRACT: Red clover is an important source of isoflavones; which has been made commercially available as dietary supplements for the treatment of menopausal symptoms. Bioavailability and metabolism of these red clover isoflavones (RCI) have not been studied in detail. Fructooligosaccharides (FOS) stimulate the growth of intestinal bacteria and play an important role in the formation of certain isoflavone metabolites, such as equol and O-desmethylangolensin. To determine the bioavailability of RCI metabolites and analyze whether FOS supplementation could influence their bioavailability. Seventeen healthy adults were enrolled in the study carried out in two periods. In the first, compound bioavailability was determined after consumption of 80mg of RCI (MF11RCE). In the second, a 6-day supplementation of 2×3000mg/day of FOS was administered before isoflavone consumption. Biochanin A and formononetin were rapidly absorbed and both reached maximum concentrations at an average of 5-7h. Demethylation was a major reaction in the metabolic pathway. Daidzein serum level peaked after about 12.6h. Supplementation with FOS led to a significant decrease in the bioavailability of daidzein, dihydroformononetin, dihydrogenistein and dihydrodaidzein. An increase in equol production was also observed which did not reach statistical significance (p>0.05). This study is the first to provide detailed data on RCI bioavailability in humans and determine no influence of FOS yet a trend toward increased equol production. More research is warranted involving a greater sample size. Copyright © 2015. Published by Elsevier B.V.
    Fitoterapia 06/2015; 105. DOI:10.1016/j.fitote.2015.06.011 · 2.35 Impact Factor
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    • "Similar to phytoestrogen, daidzein, the precursor of O-DMA, may possess biphasic activity (inhibitory at high concentrations and stimulatory at low concentrations) (15,16). Although O-DMA has only a weak affinity for the estrogen receptor (17–19), the exposure to O-DMA in the present study resulted in slightly increased MCF-7 cell growth after only 24 h. Thus, O-DMA may be a more promising anticancer candidate than its precursor. "
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    ABSTRACT: The aim of the present study was to investigate the anticancer effect of O-desmethylangolensin (O-DMA) by assessing cell proliferation, apoptosis and cell cycle distribution, as well as exploring the mechanisms underlying these effects in breast carcinoma MCF-7 cells. The cells were exposed to O-DMA (5-200 μM) for 24, 48 and 72 h. The results revealed that cell proliferation was significantly inhibited in a dose-dependent manner following treatment for 48 and 72 h, but not after 24 h, and resulted in the significant induction of apoptosis and the promotion of cell cycle arrest at the G1/S and G2/M phases. To elucidate these effects of O-DMA, the expression levels of cell cycle regulators were measured in the cells exposed to O-DMA at 150 μM for 72 h. Of the G1/S phase-related proteins, O-DMA modulated the cyclin-dependent kinases (CDKs), with a decrease in CDK2 and CDK4 and an increase in CDK6, and downregulated cyclin D and E. With respect to the G2/M-related proteins, O-DMA caused a reduction in CDK1, together with a slight increase in cyclin A and B. In addition, O-DMA downregulated p21(Cip1) and p27(Kip1), but not p16(INK4a) and p15(INK4b), and interacted with the CDK6-cyclin D and CDK1-cyclin B complexes. In conclusion, these results indicate for the first time that the regulation of the CDK4/6-cyclin D and CDK1-cyclin B complexes may participate in the anticancer activity pathway of O-DMA in MCF-7 cells.
    Oncology letters 12/2013; 6(6):1784-1788. DOI:10.3892/ol.2013.1601 · 1.55 Impact Factor
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    • "The data on the skeletal effects of T. pratense extracts are very limited, but there are numerous reports on skeletal effects of soy isoflavones. The most abundant soy isoflavones (aglycones) are genistein and daidzein, and the main Trifolium isoflavones, biochanin A and formononetin, are metabolized to genistein and daidzein, respectively, in mammalian organisms [27]. Nevertheless, the results of studies on soy product effects on the skeletal system in humans are inconsistent [28–32]. "
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    ABSTRACT: Some plant species belonging to Trifolium L. genus are a source of isoflavones considered to exert phytoestrogenic activities. The aim of the present study was to examine the effects of standardized extract obtained from aerial parts of Trifolium medium L., in comparison with the extract of Trifolium pratense L., on the development of estrogen deficiency-induced osteoporosis in rats. Both Trifolium extracts, at doses corresponding to 10 and 20 mg/kg of isoflavone aglycones daily, or estradiol (0.2 mg/kg daily), were administered orally to ovariectomized (OVX) rats for 4 weeks. Serum bone turnover markers, bone mass, mineralization, and mechanical properties were studied. In OVX control rats, mechanical properties of the tibial metaphysis and femoral neck were strongly worsened in comparison with sham-operated control rats, and those of femoral diaphysis were unaffected. Estradiol counteracted the worsening of the tibial strength and increases in bone turnover markers. Both extracts significantly increased the strength of the femoral diaphysis and calcium and phosphorus content in the bone mineral, but only T. pratense extract increased the strength of the tibial metaphysis. In conclusion, effects of both Trifolium extracts differed from those of estradiol. It is possible that other than isoflavone extract constituents contributed to their skeletal effects.
    Evidence-based Complementary and Alternative Medicine 11/2012; 2012(1):921684. DOI:10.1155/2012/921684 · 1.88 Impact Factor
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