phytoestrogens and naringenin

To examine the efficacy of a hop extract (standardized at 100mug 8-prenylnaringenin per day) for relief of menopausal discomforts.. A 16-week randomized, double-blind, placebo-controlled, cross-over study was conducted with 36 menopausal women. The participants were randomly allocated to either placebo or active treatment (hop extract) for a period of eight weeks after which treatments were switched for another eight weeks. The Kupperman Index (KI), the Menopause Rating Scale (MRS) and a multifactorial Visual Analogue Scale (VAS) were assessed at baseline, and after eight and sixteen weeks.. After 8 weeks, both active treatment and placebo significantly improved all outcome measures when compared to baseline with somewhat higher average reductions for placebo than for the active treatment. After 16 weeks only the active treatment after placebo further reduced all outcome measures, whereas placebo after active treatment resulted in an increase for all outcome measures. Although, the overall estimates of treatment efficacy (active treatment-placebo) based on linear mixed models do not show a significant effect, time-specific estimates of treatment efficacy indicate significant reductions for KI (P = 0.02) and VAS (P = 0.03) and a marginally significant reduction (P = 0.06) for MRS after 16 weeks.. Whereas the first treatment period resulted in similar reductions in menopausal discomforts in both treatment groups, results from the second treatment period suggest superiority of the standardized hop extract over placebo. Thus, phytoestrogen preparations containing this standardized hop extract may provide an interesting alternative to women seeking relief of mild vasomotor symptoms.

Topics: Cross-Over Studies; Double-Blind Method; Female; Flavanones; Humans; Humulus; Menopause; Middle Aged; Pain Measurement; Phytoestrogens; Phytotherapy; Pilot Projects; Plant Extracts; Reference Standards; Treatment Outcome

It has been shown that citrus flavanone naringenin and its prenyl derivative 8-prenylnaringenin (8-PN) possess various pharmacological activities in in vitro and in vivo models. Interestingly, it has been proposed that prenylation can enhance biological potentials, including the estrogen-like activities of flavonoids. The objective of this study was to investigate the anti-diabetic potential and molecular mechanism of 8-PN in streptozotocin (STZ)-induced insulin-deficient diabetic mice in comparison with naringenin reported to exhibit hypoglycemic effects. The oral administration of naringenin and 8-PN ameliorated impaired glucose homeostasis and islet dysfunction induced by STZ treatment. These protective effects were associated with the suppression of pancreatic β-cell apoptosis and inflammatory responses in mice. Moreover, both naringenin and 8-PN normalized STZ-induced insulin-signaling defects in skeletal muscles and apoptotic protein expression in the liver. Importantly, 8-PN increased the protein expression levels of estrogen receptor-α (ERα) in the pancreas and liver and of fibroblast growth factor 21 in the liver, suggesting that 8-PN could act as an ERα agonist in the regulation of glucose homeostasis. This study provides novel insights into the mechanisms underlying preventive effects of naringenin and 8-PN on the impairment of glucose homeostasis in insulin-deficient diabetic mice.

Topics: Animals; Apoptosis; Blood Glucose; Diabetes Mellitus, Experimental; Estrogen Receptor alpha; Estrogens; Flavanones; Glucose; Hypoglycemic Agents; Insulin; Mice; Phytoestrogens; Streptozocin

The potential utilization of plant secondary metabolites possessing estrogenic properties as alternatives to the classical hormone replacement therapy (HRT) for the relief of postmenopausal complaints asks for an evaluation regarding the safety in reproductive organs. In order to contribute to the estimation of the safety profile of the flavanones naringenin (Nar), 8‑prenylnaringenin (8PN) and 6‑(1,1‑dimethylally) naringenin (6DMAN), we investigated uterus and vagina derived from a three‑day uterotrophic assay in rats. Also, we investigated the metabolite profile resulting from the incubation of the three substances with liver microsomes. While no metabolites were detectable for naringenin, hydroxylation products were observed for 8PN and 6DMAN after incubation with human as well as rat liver microsomes. The parent compound naringenin did not evoke any estrogenic responses in the investigated parameters. A significant increase of the uterine wet weight, uterine epithelial thickness and proliferating vaginal cells was observed in response to 8PN, questioning the safety of 8PN if applied in the human situation. In contrast, no estrogenic effects on the reproductive organs were observed for 6DMAN in the conducted study, rendering it the compound with a more promising safety profile, therefore justifying further investigations into its efficacy to alleviate postmenopausal discomforts.

Topics: Animals; Cell Proliferation; Epithelium; Estradiol; Estrogens; Female; Flavanones; Humans; Microsomes, Liver; Phytoestrogens; Rats; Rats, Inbred Lew; Rats, Sprague-Dawley; Uterus; Vagina

Activation of estrogen receptor-β (ERβ) is an important mechanism for colon cancer prevention. Specific sorghum varieties that contain flavones were shown to activate ER in non-malignant colonocytes at low concentrations. This study aimed to determine positive interactions among estrogenic flavonoids most relevant in sorghum. Apigenin and naringenin were tested separately and in combination for their ability to influence ER-mediated cell growth in non-malignant young adult mouse colonocytes (YAMC). Sorghum extracts high in specific flavanones and flavones were also tested. Apigenin reduced ER-mediated YAMC cell growth comparable to physiological levels of estradiol (E₂, 1 nM) at 1 μM; naringenin had similar effect at 10 μM. However, when combined, 0.1 μM apigenin plus 0.05 μM naringenin produced similar effect as 1 nM E₂; these concentrations represented 1/10th and 1/200th, respectively, of the active concentrations of apigenin and naringenin, demonstrating a strong enhanced action. A sorghum extract higher in flavones (apigenin and luteolin) (4.8 mg g(-1)) was more effective (5 μg mL(-1)) at activating ER in YAMC than a higher flavanone (naringenin and eriodictyol) (28.1 mg g(-1)) sorghum extract (10 μg mL(-1)). Enhanced actions observed for apigenin and naringenin were adequate to explain the level of effects produced by the high flavone and flavanone sorghum extracts. Strong positive interactions among sorghum flavonoids may enhance their ability to contribute to colon cancer prevention beyond what can be modeled using target compounds in isolation.

Topics: Animals; Anticarcinogenic Agents; Apigenin; Cell Line; Cell Proliferation; Colon; Colonic Neoplasms; Drug Synergism; Estrogen Receptor Antagonists; Estrogen Receptor beta; Flavanones; Functional Food; Intestinal Mucosa; Luteolin; Mice; Osmolar Concentration; Phytoestrogens; Pigments, Biological; Plant Extracts; Seeds; Sorghum

Previous studies have found that 8-prenylflavonoids have a higher osteogenic activity than do flavonoids, which suggested that the 8-prenyl group may play an active role in bone-protective properties. To address this hypothesis, activities of 8-prenylnaringenin (PNG) and naringenin (NG) in osteoblast and osteoclast differentiation and function were compared in vitro. PNG was found to have a stronger ability than NG to improve osteoblast differentiation and osteogenic function in cultured rat calvarial osteoblasts, as demonstrated by levels of alkaline phosphatase activity, osteocalcin, calcium deposition, and the number and area of mineralized bone nodules, as well as mRNA expression of osteogenesis-related genes Bmp-2, OSX, and Runx-2. In addition, although expression of osteoclastogenic inducer receptor activator of nuclear factor kappa-B ligand (RANKL) was not affected, that of osteoclastogenesis inhibitor osteoprotegerin (OPG) and consequently the OPG/RANKL ratio were increased, more potently by PNG than NG. PNG was also found to have a higher potency than NG in inhibiting the osteoclast formation in rabbit bone marrow cells and their resorptive activity, as revealed by lower numbers of osteoclasts formed, lower numbers and areas of bone resorption pits, and lower mRNA expression levels of tartrate-resistant acid phosphatase and cathepsin K. Furthermore, PNG induced apoptosis of mature osteoclasts at a higher degree and at an earlier time than did NG. These results indicate that the 8-prenyl group plays an important role and contributes to the higher bone-protective activity of PNG in comparison with NG.

Topics: Animals; Apoptosis; Base Sequence; Bone Density; Bone Resorption; Cell Differentiation; Cells, Cultured; Flavanones; Gene Expression; Osteoblasts; Osteoclasts; Osteogenesis; Osteoprotegerin; Phytoestrogens; Rabbits; RANK Ligand; Rats; RNA, Messenger; Structure-Activity Relationship

Evidence indicates sorghum may be protective against colon cancer; however, the mechanisms are unknown. Estrogen is believed to protect against colon cancer development by inducing apoptosis in damaged nonmalignant colonocytes. Three sorghum extracts (white, red, and black) were screened for estrogenic activity using cell models expressing estrogen receptor α (ER-α; MCF-7 breast cancer cells) and β [ER-β; nonmalignant young adult mouse colonocytes (YAMC)]. Black and white sorghum extracts had significant estrogenic activity mediated through both estrogen receptors at 1-5 and 5-10 μg/mL, respectively; but red sorghum did not. Activation of ER-β in YAMC reduced cell growth via induction of apoptosis. Only the black and red sorghums contained 3-deoxyanthocyanins; however, these compounds were non-estrogenic. Flavones with estrogenic properties, luteolin (0.41-2.12 mg/g) and apigenin (1.1-1.4 mg/g), and their O-methyl derivatives (0.70-0.95 mg/g) were detected in white and black sorghums, but not in the red sorghum. On the other hand, naringenin, a flavanone known to interfere with transcriptional activities of estrogen, was only detected in the red sorghum extract (as its 7-O-glycoside) at relatively high concentration (11.8 mg/g). Sorghum flavonoid composition has important implications on possible modes of chemoprotection by sorghum against colon carcinogenesis.

Topics: Animals; Apigenin; Apoptosis; Cell Line, Tumor; Cell Proliferation; Colon; Epithelial Cells; Estrogen Receptor alpha; Female; Flavanones; Humans; Luteolin; Mice; Phytoestrogens; Plant Extracts; Sorghum

A number of recent studies have suggested that flavonols (a class of phytochemical with many biological activities), might exert protective effects against post-menopausal bone loss. In the present study, we compared naringenin (NG) and 8-prenylnaringenin (PNG), two major naturally occurring flavonols, on in vitro differentiation of osteoblasts and bone resorbing activity, of rat bone marrow stromal cells (BMSCs). Our results indicated that both compounds, at 10(-6)  m, enhanced BMSCs' differentiation. Then effects of the two compounds at 10(-6)  m on ALP activity, osteocalcin secretion and calcium deposition, were compared over a time course. Numbers and areas of colonies stained for ALP (CFU-F(ALP) ) expression, and mineralized bone nodules, were histochemically analysed after 12 days and 16 days osteogenic induction, respectively. Expression of BMP-2, OPG, OSX, RUNX-2 genes and p38MAPK protein were examined using real-time PCR and western blotting, respectively. The data presented indicate that PNG, significantly enhanced the rat BMSCs' differentiation and mineralization through the BMP-2/p38MAPK/Runx2/Osterix signal pathway, greater than did NG. In conclusion, PNG has a more pronounced ability to enhance osteoblast differentiation and mineralization, than NG.

Topics: Alkaline Phosphatase; Animals; Cell Differentiation; Cells, Cultured; Estrogen Antagonists; Flavanones; Gene Expression Regulation, Developmental; Male; Mesenchymal Stem Cells; Osteoblasts; Osteocalcin; Osteogenesis; Phytoestrogens; Rats; Rats, Wistar; Signal Transduction

A variety of plant derived substances, so-called phytoestrogens (PEs), although structurally not related to steroids, produce effects similar to the mammalian estradiol. However, little is known so far about the structural requirements which determine PE activities. Taking into consideration that prenylation reactions are relatively common in plant secondary metabolism, the activity of a set of three PE derivatives of genistein and naringenin, namely genistein, 8-prenylgenistein (8PG), 6-(1,1-dimethylallyl)genistein (6DMAG), naringenin, 8-prenylnaringenin (8PN) and 6-(1,1-dimethylallyl)naringenin (6DMAN) was compared regarding structure-estrogenicity relationships in three functionally different estrogen receptor assays. Strong estrogenic activities were recorded for 6DMAN and 8PN in all assays used, while the parent compound naringenin showed only very weak estrogenicity. In contrast, in the case of genistein derivatives, only genistein itself exhibited estrogenic activity in a yeast based assay. In MVLN breast cancer cells, a bioluminescent MCF-7-derived cell line, the estrogenic activity of all three genistein derivatives was similar. Studying alkaline phosphatase activity in Ishikawa endometrial cancer cells as an estrogenic response marker revealed a similar pattern of estrogenicity of the genistein derivatives compared to the yeast based assay although a slight estrogenic effect of 6DMAG and 8PG was apparent. In summary, this study demonstrates that prenylation often found in plant secondary metabolism differentially modifies estrogenic properties of PEs depending on the basic structure of the respective PE.

Topics: Alkaline Phosphatase; Animals; beta-Galactosidase; Cell Line, Tumor; Estradiol; Estrogen Receptor alpha; Estrogens; Flavanones; Gene Expression; Genes, Reporter; Genistein; Humans; Luciferases; Phytoestrogens; Prenylation; Promoter Regions, Genetic; Response Elements; Saccharomyces cerevisiae; Transfection; Vitellogenins; Xenopus

Many flavonoids, a major group of phenolic plant-derived secondary metabolites, are known to possess estrogen-like bioactivities. However, little is known about their estrogenic properties in the central nervous system due to the lack of suitable cellular models expressing sufficient amounts of functional estrogen receptor beta (ERbeta). To overcome this deficit, we have created a cellular model, which is serotonergic in origin, to study properties of estrogenic substances by stably transducing RN46A-B14 cells derived from raphe nuclei region of the rat brain with a lentiviral vector encoding a human ERbeta. We clearly showed that the transgenic human ERbeta is a spontaneously expressed and a functional receptor. We have further assessed the estrogenicity of three different isoflavones and four different naringenin-type flavanones in this cell line utilizing a luciferase reporter gene assay. Genistein (GEN), Daidzein (DAI), Equol (EQ), Naringenin (NAR) and 8-prenylnaringenin (8-PN) showed strong estrogenic activity in a concentration-dependent manner as compared to 7-(O-prenyl)naringenin-4'-acetate (7-O-PN) which was only slightly estrogenic and 6-(1,1-dimethylallyl)naringenin (6-DMAN) that neither showed estrogenic nor anti-estrogenic activity in our model. All observed effects could be antagonized by the anti-estrogen fulvestrant. Moreover, co-treatment of cells with 17beta-estradiol (E2) and either GEN or DAI showed a slight additive effect as compared to EQ. On the other hand, 8-PN in addition to 7-O-PN, but not NAR and 6-DMAN, were able to slightly antagonize the responses triggered by E2. Our newly established cellular model may prove to be a useful tool in explicating basic physiological properties of ERbeta in the brain and may help unravel molecular and cellular mechanisms involved in serotonergic mood regulation by estrogen or potential plant-derived secondary metabolites.

Topics: Animals; Cell Line; Cloning, Molecular; Estrogen Receptor beta; Flavanones; Genes, Reporter; Humans; Phytoestrogens; Raphe Nuclei; Rats; Transduction, Genetic; Transgenes

Hop is a well-known and already frequently used estrogenic phytotherapeutic, containing the interesting prenylflavonoids, xanthohumol (XN), isoxanthohumol (IXN), 8- and 6-prenylnaringenin (8-PN and 6-PN). Since the use of secondary standards can form a solution whenever the determination is required of certain components, not commercially available or too expensive, it was decided to develop an accessible HPLC-DAD method for the determination of these prenylflavonoids. The amounts were determined in hop extract and capsules, using quercetin and naringenin as secondary standards. After optimization of the sample preparation and HPLC conditions, the analysis was validated according to the ICH guidelines. The response function of XN, 8-PN, quercetin and naringenin showed a linear relationship. For the determination of XN, a calibration line of at least three concentrations of quercetin has to be constructed. The correction factors for XN (quercetin) and for 8-PN (naringenin) were validated and determined to be 0.583 for XN, and 1.296 for IXN, 8-PN and 6-PN. The intermediate precision was investigated and it could be concluded that the standard deviation of the method was equal considering time and concentration (RSD of 2.5-5%). By means of a recovery experiment, it was proven that the method is accurate (recoveries of 96.1-100.1%). Additionally, by analysing preparations containing hop extracts on the Belgian market, it was shown that the method is suitable for its use, namely the determination of XN, IXN, 8-PN and 6-PN in hop extract and capsules, using quercetin and naringenin as secondary standards.

Topics: Calibration; Capsules; Chemistry Techniques, Analytical; Chromatography, High Pressure Liquid; Flavanones; Flavonoids; Humulus; Phytoestrogens; Propiophenones; Quercetin; Reproducibility of Results; Xanthones

Phytoestrogens exhibit significant estrogen agonistic/antagonistic properties in animals and humans. Naturally occurring flavonoids with a naringenin backbone like 8-prenylnaringenin (8-PN) and 6-(1,1-dimethylallyl)naringenin (6-DMAN) are considered to be some of the most potent phytochemicals activating nuclear receptors. 8-PN is a more potent estrogenic substance while 6-DMAN appears to have a higher antiandrogenic potency, however these are less well characterized compared to other phytoestrogens such as genistein. The aim of this study was to assess the estrogenic properties of 8-PN and 6-DMAN in an ovariectomized in vivo rat model. 8-PN and 6-DMAN were applied at concentrations of 15mg/kgBW. We assessed the uterotrophic response after 7h, 24h and 72h of treatment. In contrast to 8-PN, 6-DMAN did not alter uterine wet weight or the level of expression of proliferation markers at any time point. In contrast to the uterotrophic response, 6-DMAN stimulated uterine mRNA expression of estrogen responsive genes carrying an estrogen response element (ERE) in the ovariectomized rats, but to a lesser extent than E2 and 8-PN. In all treatment regimens, the mRNA expression of estrogen receptors alpha and beta mRNA was measured. In summary, we assessed the time dependent uterine responses and estrogenic activities of 6-DMAN and 8-PN. In contrast to 8-PN which mimicked the E2 induced responses on uterine wet weight and gene expression, 6-DMAN has no uterotrophic effect and only regulated the mRNA expression of genes carrying an ERE. Therefore, 6-DMAN is an exciting candidate molecule for future investigations and potentially a natural occurring selective estrogen receptor modulator.

Topics: Animals; Cell Line, Tumor; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Flavanones; Gene Expression Regulation; Humans; Organ Size; Ovariectomy; Phytoestrogens; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Uterus

Diets rich in citrus and citrus-based products have been negatively correlated with the risk of cardiovascular disease, but so far no studies have been conducted to determine whether naringenin and hesperetin, two major flavanones in citrus plants, influence endothelium nitric oxide (NO) production. The aim of this study is to clarify estrogenic activities of naringenin and hesperetin and to examine whether they affect endothelial NO production via estrogen receptor (ER) activation. Both naringenin and hesperetin were observed to promote growth of MCF-7 cells under greatly reduced estrogen conditions and to suppress estrogen-induced response. Naringenin activated both ERalpha and ERbeta, whereas hesperetin exhibited stronger potential to activate ERalpha rather than ERbeta. Hesperetin, but not naringenin, increased NO releases from human umbilical vein endothelial cells in a dose-dependent manner. Hesperetin-induce responses were suppressed by ICI 182 780 and actinomycin D. Real-time reverse transcription polymerase chain reaction (RT-PCR) and western-blotting analysis revealed that hesperetin up-regulated endothelium nitric oxide synthase (eNOS) expression. These results suggested that hesperetin exerts an antiatherogenic effect, in part, via ER-mediated eNOS expression and subsequent increase of endothelial NO production. Distinct effects of naringenin and hesperetin on NO production also imply that ERalpha might play the major role in estrogen-induced eNOS expression. However, the inefficacy of naringenin on NO production remains to be elaborately studied. Our findings add more proof to the molecular explanations for the health benefits of citrus used to prevent cardiovascular disease, especially for postmenopausal women.

Topics: Cells, Cultured; Citrus; Endothelial Cells; Flavanones; Gene Expression; Hesperidin; Humans; Nitric Oxide; Nitric Oxide Synthase Type III; Phytoestrogens; RNA, Messenger; Umbilical Veins

A phenotypic definition of the term estrogen has become increasingly problematic due to the multiple modes of estrogen action which can now be defined by differing nuclear and membrane receptors for the classic ligand, 17beta-estradiol, and by the multiple signalling pathways that are consequently addressed. This has led to the term xenoestrogen being largely determined by whatever assay system is used for its definition. Here we describe a novel and simple matrix for a transfection system using MBA-MD231 and MCF-7 breast cancer cells as hosts. This matrix is able to vary the type of nuclear estrogen receptor used, and by varying the promoter-reporter construct between one using a classic estrogen response element (ERE) enhancer, and one using an enhancer element derived from the bovine oxytocin gene promoter binding an orphan nuclear receptor, direct classical effects can be neatly discriminated from non-classical and non-genomic actions of test substances. This assay matrix has been used to examine a selection of phytoestrogens and xenobiotics, thereby providing new information on the mechanism of action of some of these substances in breast cancer cells.

Topics: Animals; Biological Assay; Cations, Divalent; Cattle; Cell Line, Tumor; Dose-Response Relationship, Drug; Estrogens; Flavanones; Genistein; Humans; Mutant Proteins; Phytoestrogens; Promoter Regions, Genetic; Receptors, Estrogen; Resveratrol; Stilbenes; Transcription, Genetic; Xenobiotics

Phytoestrogens are plant-derived, non-steroidal constituents of our diets. They can act as agonists or antagonists of estrogen receptors, and they can modulate the activities of the key enzymes in estrogen biosynthesis. Much less is known about their actions on the androgen and progesterone metabolizing enzymes. We have examined the inhibitory action of phytoestrogens on the key human progesterone-metabolizing enzyme, 20alpha-hydroxysteroid dehydrogenase (AKR1C1). This enzyme inactivates progesterone and the neuroactive 3alpha,5alpha-tetrahydroprogesterone, to form their less active counterparts, 20alpha-hydroxyprogesterone and 5alpha-pregnane-3alpha,20alpha-diol, respectively. We overexpressed recombinant human AKR1C1 in Escherichia coli, purified it to homogeneity, and examined the selected phytoestrogens as inhibitors of NADPH-dependent reduction of a common AKR substrate, 9,10-phenantrenequinone, and progesterone. The most potent inhibitors were 7-hydroxyflavone, 3,7-dihydroxyflavone and flavanone naringenin with IC(50) values in the low microM range. Docking of the flavones in the active site of AKR1C1 revealed their possible binding modes, in which they are sandwiched between the Leu308 and Trp227 of AKR1C1.

Topics: 20-Hydroxysteroid Dehydrogenases; 3-Hydroxysteroid Dehydrogenases; Aldo-Keto Reductase Family 1 Member C3; Binding Sites; Computer Simulation; Coumarins; Enzyme Inhibitors; Estradiol Congeners; Estrogen Receptor Modulators; Flavanones; Flavones; Humans; Hydroxyprostaglandin Dehydrogenases; Isoflavones; Models, Biological; Models, Molecular; Phenanthrenes; Phytoestrogens; Progesterone; Progesterone Reductase; Protein Binding; Recombinant Proteins; Stilbenes; Zearalenone

The estrogenic activity of several intermediary plant compounds has raised concern about possible risks of unwanted interference with endocrine regulation, but on the other hand there are potential medical benefits, in particular in treatment of menopausal symptoms or cancer. In the present study, we compare the estrogenic effects of phytoestrogens naringenin, 8-prenylnaringenin, 6-(1,1-dimethylallyl)naringenin, and the synthetic 4'-acetyl-7-prenyloxynaringenin. Two mammalian in vitro systems and a fish in vivo system were used to study the estrogenic properties with reference to genistein, 17-beta-estradiol or ethynylestradiol. Strong differences were observed between the mammalian in vitro and the fish in vivo test system. In the medaka sex reversal/vtg gene expression assay no estrogenic effects of the naringenin-type flavonoids were observed, while mammalian in vitro systems showed a similar and graded response to the test compounds.

Topics: Animals; Breast Neoplasms; Cell Line; Dose-Response Relationship, Drug; Estrogens; Flavanones; Flavonoids; Genistein; Humans; Oryzias; Phytoestrogens; Receptors, Estrogen; Sex Differentiation; Species Specificity

Naturally occurring naringenin derivatives, known for their estrogenic activity, were tested in two independent (anti-)androgen screening assays. Using a yeast-based androgen receptor assay relatively strong antiandrogen activities were demonstrated for 6-(1,1-dimethylallyl)naringenin and 8-prenylnaringenin, while the parent compound naringenin did not show recognizable antiandrogen activity. In an androgen receptor activity assay based on the analysis of prostate specific antigen (PSA) concentrations in the supernatants of treated PC3(AR)2 cells the antiandrogenic activity of 6-(1,1-dimethylallyl)naringenin was detected at concentrations of 10 (-5) M. 8-Prenylnaringenin or naringenin have no detectable antiandrogenic effect. In summary, for the first time we provide evidence of the antiandrogenic activity of 6-DMA-N in two independent model systems. In conclusion, we demonstrated the ability of prenylated naringenins not only to act via the estrogen receptor but also through the androgen receptor.

Topics: Androgen Antagonists; Cells, Cultured; Dose-Response Relationship, Drug; Flavanones; Humans; Isoflavones; Phytoestrogens; Phytotherapy; Plant Preparations; Plants, Medicinal; Receptors, Androgen

Chemically synthesized naringenin derivatives, identical to natural occurring compounds, were tested for their estrogenic activity using two independent estrogen screening assays. Using a yeast based estrogen receptor assay, strong estrogenic activities were demonstrated for 6-(1,1-dimethylallyl)naringenin and 8-prenylnaringenin, while the parent compound naringenin did not show recognizable estrogenic activity. In MVLN cells, a bioluminescent MCF-7-derived cell line, the estrogenic activity of 8-prenylnaringenin and 6-(1,1-dimethylallyl)naringenin was detected at concentrations of 10(-6) M and 5 x 10(-6) M respectively. Naringenin demonstrated estrogenic activity but only at a concentration of 10(-5) M. These estrogenic effects are mediated by the ER, as the antiestrogen 4-hydroxytamoxifen inhibited these activities. In summary, this study provides the further confirmation that 8-prenylnaringenin demonstrates high estrogenic activity, and demonstrated for the first time for 6-(1,1-dimethylallyl)naringenin a reasonable high estrogenic activity, while naringenin exhibit low or no estrogenic activity.

Topics: Dose-Response Relationship, Drug; Estradiol Congeners; Estrogen Antagonists; Estrogens, Non-Steroidal; Flavanones; Flavonoids; Humans; Isoflavones; Molecular Structure; Phytoestrogens; Plant Preparations; Receptors, Estrogen; Tamoxifen; Tumor Cells, Cultured

The effects of 17beta-estradiol (17beta-E(2)) or the phytoestrogen naringenin on spontaneous atherosclerosis were studied in 36 ovariectomized homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits receiving a semisynthetic control diet; this diet added 0.0040% 17beta-E(2;) or 0.20% naringenin, for 16 weeks. The uterine weight was increased (P < 0.001) and the concentration of estrogen receptor alpha was decreased (P < 0.001) in the 17beta-E(2) group compared with the controls. Total plasma cholesterol and triglycerides were not different from those in the controls. In lipoproteins, HDL cholesterol was increased (P < 0.01), and LDL triglyceride and IDL triglyceride were lowered (P < 0.05). The oxidation (as concentration of malondialdehyde) was increased in LDL (P < 0.05) but not in plasma. The cholesterol accumulation was decreased (P < 0.05) in the ascending aorta and in the total aorta but the ratio of intima to media and area of intima in ascending, thoracic, and abdominal aorta were not significantly different. In the naringenin group the only differences, compared with the control group, were increased HDL cholesterol (P < 0.001) and decreased activity of glutathione reductase (P < 0.05). In conclusion, 17beta-E(2), but not naringenin, attenuated aortic cholesterol accumulation independently of plasma and LDL cholesterol. Further, these results support previously suggested pro-oxidant ability of 17beta-E(2) toward LDL and a possible connection between the pro-oxidant nature of 17beta-E(2) and its antiatherogenic effect.

Topics: Animals; Aorta; Arteriosclerosis; Cholesterol; Disease Models, Animal; Erythrocytes; Estradiol; Estrogens, Non-Steroidal; Female; Flavanones; Flavonoids; Food, Formulated; Humans; Isoflavones; Lipoproteins; Molecular Structure; Ovariectomy; Oxidation-Reduction; Phytoestrogens; Plant Preparations; Rabbits

The study investigated the ability of 34 natural and synthetic chemicals to compete with [3H]17beta-estradiol (E2) for binding to bacterially expressed glutathione-S-transferase (GST)-estrogen receptors (ER) fusion proteins from five different species. Fusion proteins consisted of the ER D, E and F domains of human alpha (GST-hERalphadef), mouse alpha (GST-mERalphadef), chicken (GST-cERdef), green anole (GST-aERdef) and rainbow trout ERs (GST-rtERdef). All five fusion proteins displayed high affinity for E2 with dissociation constants (K(d)) ranging from 0.3 to 0.9 nM. Although, the fusion proteins exhibited similar binding preferences and binding affinities for many of the chemicals, several differences were observed. For example, alpha-zearalenol bound with greater affinity to GST-rtERdef than E2, which was in contrast to other GST-ERdef fusion proteins examined. Coumestrol, genistein and naringenin bound with higher affinity to the GST-aERdef, than to the other GST-ERdef fusion proteins. Many of the industrial chemicals examined preferentially bound to GST-rtERdef. Bisphenol A, 4-t-octylphenol and o,p' DDT bound with approximately a ten-fold greater affinity to GST-rtERdef than to other GST-ERdefs. Methoxychlor, p,p'-DDT, o,p'-DDE, p,p'-DDE, alpha-endosulfan and dieldrin weakly bound to the ERs from the human, mouse, chicken and green anole. In contrast, these compounds completely displaced [3H]E2 from GST-rtERdef. These results demonstrate that ERs from different species exhibit differential ligand preferences and relative binding affinities for estrogenic compounds and that these differences may be due to the variability in the amino acid sequence within their respective ER ligand binding domains.

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Chickens; Cloning, Molecular; Coumestrol; Dieldrin; Estrogen Receptor Modulators; Estrogens; Estrogens, Non-Steroidal; Flavanones; Flavonoids; Genistein; Humans; Isoflavones; Lizards; Methoxychlor; Mice; Molecular Sequence Data; Mycotoxins; Oncorhynchus mykiss; Phytoestrogens; Plant Preparations; Receptors, Estrogen; Recombinant Fusion Proteins; Sequence Homology, Amino Acid; Species Specificity

This study reports on some environmental chemicals with estrogenic activity (xenoestrogens) and their binding interaction for human plasma sex-hormone binding globulin (hSHBG). The binding affinity constant of these xenoestrogens was measured in equilibrium conditions by solid phase binding assay, and their ability to displace endogenous testosterone and estradiol from hSHBG binding sites was determined with an ammonium sulfate precipitation assay in native plasma from normal men and women. The data showed that some of these xenoestrogens bind hSHBG, with a reversible and competitive binding activity for both [3H]testosterone and [3H]17beta-estradiol and with no apparent decrease in the number of hSHBG binding sites. Their respective binding affinity constants were low, ranging from 0.02 to 7.8 10(5) 1 x mol(-1). However, in native plasma from normal men and women, they were able to dose-dependently increase concentrations of hSHBG-unbound testosterone and/or estradiol. In this study, 4-nonylphenol and 4-tertoctylphenol, two alkylphenols used as surfactants in many commercial products, and bisphenol A and O-hydroxybiphenyl, widely used in the plastics industry, were identified as potent hSHBG-ligands. Additionally, the flavonoid phytoestrogens genistein and naringenin were also identified as hSHBG ligands, whereas their glucoside derivatives, genistin and naringin, had no binding activity for hSHBG. From these data, it is suggested that hSHBG binding may transport some contaminant xenoestrogens into the plasma and modulate their bioavailability to cell tissues. On the other hand, xenoestrogens may also displace endogenous sex steroid hormones from hSHBG binding sites and disrupt the androgen-to-estrogen balance. Whether xenoestrogen SHBG ligands could reach high enough concentrations in the blood to expose humans to any such effect merits further investigation.

Topics: Binding, Competitive; Estradiol; Estrogens; Estrogens, Non-Steroidal; Female; Flavanones; Flavonoids; Genistein; Humans; Isoflavones; Male; Phenols; Phytoestrogens; Plant Preparations; Sex Hormone-Binding Globulin; Testosterone; Xenobiotics