Synthesis of hapten and conjugates of coumestrol and development of immunoassay

3-O-Carboxymethylcoumestrol was prepared as the hapten for immunoassay by a partial alkylation of coumestrol with ethyl chloroacetate in acetone alkalized with potassium carbonate. 3-O-Ethoxycarbonylmethylcoumestrol was separated by column chromatography and finally was hydrolyzed with formic acid. 1H and 13C NMR data (APT, COSY, HMQC, and HMBC) revealed that the reaction was regioselective, as 3-O-ethoxycarboxymethylcoumestrol was the only monosubstituted derivative. The hapten was then conjugated to bovine serum albumin and used for immunization of rabbits. A radioimmunoassay (RIA) system was established based on the polyclonal antiserum and a 125I-labeled hapten-tyrosine methyl ester conjugate as the radioligand. Parameters of the RIA: sensitivity: 12 pg per tube, 50% intercept: 140 pg per tube, working range: 20-4000 pg per tube. The cross-reactivity of a panel isoflavonoid and lignan phytoestrogens was either negligible (e.g. formononetin 0.07%; biochanin A 0.06%) or not detectable at all. The major immunoreactive peak in HPLC fractions from an alfalfa extract had the same retention time as coumestrol standard and represented 94.8% of the signal. The remaining 5.2% of immunoreactivity was distributed between five minor peaks. We conclude that after the validation for particular matrices, the method will be a useful tool for analysis of coumestrol, especially in low volume and low concentration samples.     

Uptake and metabolism of enterolactone and enterodiol by human colon epithelial cells

The enterolignans enterolactone and enterodiol are phytoestrogens that are formed from plant lignans by microorganisms in the human colon. Enterolignans circulate in plasma as conjugates. We hypothesized that conjugation of enterolignans takes place in colon epithelial cells, and studied the time course of uptake and metabolism of enterolactone and enterodiol in three human colon epithelial cell lines. In addition, the conjugates were identified by mass spectrometry with accurate mass measurement (LC/QTOFMS/MS). Intracellular levels of conjugated enterolactone and enterodiol in HT29 cells rose immediately after starting the exposure. This was accompanied by a rapid decrease in free enterolactone and enterodiol in the exposure medium of HT29 and (un)differentiated CaCo-2 but not of CCD841CoTr cells. Conjugation and excretion of enterolactone and enterodiol was complete within 8 h, except for enterodiol in CaCo-2 cells ( approximately 48 h). Enterolactone appears to be more rapidly metabolized and/or excreted than enterodiol, and also the appearance of conjugated enterolactone in medium is less affected by the presence of enterodiol than vice versa. Total (free plus conjugated) enterolignan concentrations remained constant throughout the experiments. Three conjugates were identified in exposure medium of HT29 cells: enterolactone-sulfate, enterolactone-glucuronide, and enterodiol-glucuronide.Taken together, our data suggest that phase II metabolism of enterolactone and enterodiol already may take place during uptake in the colon and that colon epithelial cells may be responsible for this metabolism.     

Xanthohumol and related prenylflavonoids from hops and beer: to your good health!

Xanthohumol (3'-[3,3-dimethyl allyl]-2',4',4-trihydroxy-6'-methoxychalcone) is the principal prenylated flavonoid of the female inflorescences of the hop plant ('hops'), an ingredient of beer. Human exposure to xanthohumol and related prenylflavonoids, such as 8-prenylnaringenin and isoxanthohumol, is primarily through beer consumption. Xanthohumol has been characterized a 'broad-spectrum' cancer chemopreventive agent in in vitro studies, while 8-prenylnaringenin enjoys fame as the most potent phytoestrogen known to date. These biological activities suggest that prenylflavonoids from hops have potential for application in cancer prevention programs and in prevention or treatment of (post-)menopausal 'hot flashes' and osteoporosis. Xanthohumol and 8-prenylnaringenin are metabolized into many flavonoid derivatives with modified 3,3-dimethyl allyl (prenyl) moieties. Xanthohumol is formed in lupulin glands by a specialized branch of flavonoid biosynthesis that involves prenylation and O-methylation of the polyketide intermediate chalconaringenin. Although a lupulin gland-specific chalcone synthase is known, the aromatic prenyltransferase and O-methyltransferase participating in xanthohumol have not been identified. The prenylflavonoid pathway is a possible target for breeding or biotechnological modification of hops with the aim of increasing xanthohumol levels for beer brewing and 8-prenylnaringenin levels for pharmaceutical production.     

Combinatory effects of phytoestrogens and 17beta-estradiol on proliferation and apoptosis in MCF-7 breast cancer cells

Phytoestrogens have been described to be weak estrogens, SERMs or exhibit antiestrogenic properties. However, information about their activity in presence of estrogens is limited. Therefore, we have analysed the dose dependent combinatory activity of the phytoestrogens genistein (Gen), daidzein (Dai) and coumestrol (Cou), and 17ß-estradiol (E2) on cell proliferation and apoptosis induction in human MCF-7 breast cancer cells. Neither additive nor antagonistic effects on proliferation could be observed, but in contrast all phytoestrogens possessed the ability to inhibit apoptosis in the presence of 17ß-estradiol.

In summary, our in vitro results demonstrate that Gen does not exhibit any antiestrogenic properties. The additive growth stimulatory effects of Gen, Dai and Cou in the presence of E2 are not the result of a stimulation of proliferation; these phytoestrogens, at least in MCF-7 cells, could be characterised as inhibitors of apoptosis.     

Effects of genistein in the maternal diet on reproductive development and spatial learning in male rats

Endocrine disruptors, chemicals that disturb the actions of endogenous hormones, have been implicated in birth defects associated with hormone-dependent development. Phytoestrogens are a class of endocrine disruptors found in plants. In the current study we examined the effects of exposure at various perinatal time periods to genistein, a soy phytoestrogen, on reproductive development and learning in male rats. Dams were fed genistein-containing (5 mg/kg feed) food during both gestation and lactation, during gestation only, during lactation only, or during neither period. Measures of reproductive development and body mass were taken in the male offspring during postnatal development, and learning and memory performance was assessed in adulthood. Genistein exposure via the maternal diet decreased body mass in the male offspring of dams fed genistein during both gestation and lactation, during lactation only, but not during gestation only. Genistein decreased anogenital distance when exposure was during both gestation and lactation, but there was no effect when exposure was limited to one of these time periods. Similarly, spatial learning in the Morris water maze was impaired in male rats exposed to genistein during both gestation and lactation, but not in rats exposed during only one of these time periods. There was no effect of genistein on cued or contextual fear conditioning. In summary, the data indicate that exposure to genistein through the maternal diet significantly impacts growth in male offspring if exposure is during lactation. The effects of genistein on reproductive development and spatial learning required exposure throughout the pre- and postnatal periods.     

Insight into estrogenicity of phytoestrogens using in silico simulation

Phytoestrogens, including miroestrol and deoxymiroestrol, have the ability to act through competition with estrogen for binding to the estrogen receptor (ER). Here, we utilize manual ligand docking followed by molecular dynamics simulations and binding free energy calculations with the linear interaction energy method to predict the binding modes and the binding affinities of phytoestrogens on the ligand binding domain of ER (ERα-LBD). The calculations brought about the good correlation between the calculated binding free energy and the bioassays. Furthermore, consideration of Lennard-Jones and Coulomb interaction energies of miroestrol and deoxymiroestrol on ERα-LBD provided the information to develop the phytoestrogen derivatives as the preferred drug for ER positive breast cancer treatment.     

Experimentally induced mastitis and metritis modulate soy bean derived isoflavone biotransformation in diary cows

The present study compared the changes in isoflavone (daidzein and genistein) and their metabolite (equol and para-ethyl-phenol) concentrations in the blood plasma of cows with induced mastitis and metritis after feeding with soy bean. Sixteen cows were divided into four groups: control for mastitis group, cows with induced mastitis group, control for metritis group, and cows with induced metritis group. All cows were fed a single dose of 2.5 kg of soy bean and then blood samples were taken from the jugular vein for 8 h at predetermined intervals. The concentrations of soy bean-derived isoflavones and their active metabolites were measured in the blood plasma on HPLC system. β-Glucuronidase activity in the blood plasma of cows was measured by fluorometric method. In the blood plasma of cows with induced mastitis and metritis, we found considerably higher concentrations and time-dependent increase in isoflavone metabolites (equol and para-ethyl-phenol) with reference to cyclic cows (P < 0.05). Moreover, we noticed significant decrease of genistein in the blood plasma of the cows with induced metritis compared with control cows (P < 0.05). In addition, in the blood plasma of the cows with induced metritis, we found an increase in β-glucuronidase activity compared with control cows (P < 0.05). In conclusion, health status of the females influenced the concentrations of isoflavone metabolites in the blood plasma of the cows. Experimentally induced mastitis and metritis increased isoflavone absorption, biotransformation and metabolism. Therefore, we suggest that cows with induced mastitis and metritis are more exposed to active isoflavone metabolite actions than healthy cows.     

白藜芦醇对乳腺癌细胞MCF-7增殖的影响

目的：研究白藜芦醇体外活性,确定它的植物雌激素作用。方法：采用MTT法观察不同浓度白藜芦醇对MCF-7细胞增殖作用的影响。采用DNA ladder法和荧光显微镜观察高浓度白藜芦醇对细胞的影响。免疫组化法观察低浓度白藜芦醇对核增殖抗原PCNA表达的影响。结果：MTT结果显示白藜芦醇高浓度抑制MCF-7细胞增殖,IC50为8.70×10-5mol/L;低浓度（10-7~10-6mol/L）则对细胞有促增殖作用,最高促增殖浓度为1.0×10-7mol/L。DNA ladder和荧光显微镜可观察到高浓度白藜芦醇作用后细胞典型的凋亡形态。免疫组化结果显示低浓度白藜芦醇作用后,细胞核内PCNA表达明显增加（P〈0.05）。结论：高、低浓度的白藜芦醇对MCF-7细胞分别表现为诱导凋亡和促增殖作用,呈现出植物雌激素对MCF-7细胞典型的双向调节作用。     

A soy supplement and tamoxifen inhibit sexual behavior in female rats

In addition to displaying proceptive (hopping and darting) and receptive (lordosis) behaviors during a sexual encounter with a male, female rodents will regulate the timing of the encounter by engaging in a series of approaches and withdrawals from the male, a behavior termed paced mating behavior. Proceptive, receptive, and paced mating behaviors are all regulated by, and sensitive to, estrogen and progesterone, suggesting that compounds capable of disrupting these critical hormones may also perturb the display of female sexual behavior. The present experiments examined the impact of the selective estrogen receptor modulator (SERM) tamoxifen and a popular soy phytoestrogen dietary supplement on female sexual behavior in rats. Ovariectomized female rats were given either tamoxifen (TAMOX) by implant or the soy supplement through the diet then injected with estradiol benzoate (EB, 10 microg) or oil followed 48 h later with an injection of progesterone (P, 500 microg). Animals were then tested for sexual behavior 4 h after the P injection. Neither compound had any effect on sexual behavior when administered in conjunction with P alone; however, both significantly diminished receptive behavior, as measured by the lordosis quotient (LQ), in animals primed with both EB and P. Similarly, the hopping and darting rate was also significantly depressed in both the soy- and TAMOX-treated animals, compared to the EB- and P-treated controls, with the soy-treated animals showing significantly less proceptive behavior than the TAMOX-treated animals. Finally, soy but not TAMOX significantly attenuated paced mating behavior in animals compared to the EB- and P-treated controls. These results demonstrate that both the soy supplement and TAMOX act as estrogen antagonists on both proceptive and receptive behavior in female rats.