Potentially hallucinogenic 5‐hydroxytryptamine receptor ligands bufotenine and dimethyltryptamine in blood and tissues

Bufotenine and N,N-dimethyltryptamine (DMT) are hallucinogenic dimethylated indolethylamines (DMIAs) formed from serotonin and tryptamine by the enzyme indolethylamine N-methyltransferase (INMT) ubiquitously present in non-neural tissues. In mammals, endogenous bufotenine and DMT have been identified only in human urine. The DMIAs bind effectively to 5HT receptors and their administration causes a variety of autonomic effects, which may reflect their actual physiological function. Endogenous levels of bufotenine and DMT in blood and a number of animal and human tissues were determined using highly sensitive and specific quantitative mass spectrometric techniques. A new finding was the detection of large amounts of bufotenine in stools, which may be an indication of its role in intestinal function. It is suggested that fecal and urinary bufotenine originate from epithelial cells of the intestine and the kidney, respectively, although the possibility of their synthesis by intestinal bacteria cannot be excluded. Only small amounts of the DMIAs were found in somatic or neural tissues and none in blood. This can be explained by rapid catabolism of the DMIAs by mitochondrial monoamino-oxidase or by the fact that the dimethylated products of serotonin and tryptamine are not formed in significant amounts in most mammalian tissues despite the widespread presence of INMT in tissues.

Familial correlations, segregation analysis, and nongenetic correlates of soy isoflavone-metabolizing phenotypes

Particular intestinal bacteria metabolize the soy isoflavone daidzein to equol and O-desmethylangolensin (O-DMA), metabolites that can be identified in urine. Individuals that harbor bacteria capable of producing equol or O-DMA are known as equol producers (approximately 30%-50% of the population) and O-DMA producers (approximately 80%-90% of the population), respectively. The equol-producer phenotype has been associated with sex hormone-related outcomes in several studies. However, the bacteria responsible for these phenotypes have not yet been identified and factors that influence the manifestation of these phenotypes are not well understood. To evaluate familial clustering of and nongenetic factors associated with these phenotypes, 410 individuals from 112 families participated in phenotyping (3-day soy challenge and Day 4 spot urine collection). In segregation analyses of the equol-producer phenotype, the Mendelian dominant model provided the most parsimonious fit to the data, suggesting that the pattern of inheritance of the equol-producer phenotype is consistent with an autosomal dominant trait. This phenotype was positively associated with education (p trend = 0.01), but not with sex, smoking, or several dietary factors. Results of the segregation analyses of the O-DMA-producer phenotype were inconclusive; no other models provided a more parsimonious fit to the data than the general model. This phenotype was inversely associated with age in a nonlinear model (p = 0.01), positively associated with age- and sex-adjusted height (odds ratio [OR] 10-cm increase = 0.38, 95% confidence interval [CI] = 0.15, 0.95) and body mass index (kg/m(2)) (OR = 0.91, 95% CI = 0.85, 0.96), but not with sex, education, smoking, or several dietary factors. These results suggest the equol-producer phenotype may be under some degree of genetic control and that there are likely other environmental factors not evaluated in the present analysis that contribute to both of these phenotypes. These results provide a foundation for further work to refine our understanding of heritable and environmental determinants of daidzein-metabolizing phenotypes.

Deuterated phytoestrogen flavonoids and isoflavonoids for quantitation

Isotopically and isomerically pure polydeuterated flavonoids and isoflavonoids have been prepared for quantitation of these compounds in biological matrices. Various deutero-labeling techniques are presented and methods for establishing the isotopical and isomerical purity of deuterated products are discussed.

Enterolignans

A review with 114 references about mammalian lignans (enterolignans). Several aspects have been reviewed: the precursors of mammalian lignans and their biosynthesis, biological activities and health effects, metabolism (in vivo and in vitro) in human and animals, some synthetic strategies to obtain enterolignan skeleton types, including the synthesis of haptens and deuterated lignans, and finally an overview of the analytical methods to detect and quantify lignans in biological matrices and foods.

Identification and quantification of polyphenol phytoestrogens in foods and human biological fluids

We review the methods used to measure phytoestrogens (genistein, daidzein, lignans and their derivatives) in foods and biological fluids, and discuss advantages and disadvantages of each. The range of detection limits reported varies widely between individual laboratories, but generally the best reported sensitivity is as follows: immunoassay>HPLC-mass spectrometry=HPLC-multichannel electrochemical detection (coularray)>GC-single ion monitoring-mass spectrometry>HPLC-UV diode array>HPLC-single channel electrochemical detection. The best sensitivity reported so far is 0.002 pmol per assay for daidzein by radioimmunoassay. HPLC with UV diode array detection is the most commonly employed, but is the least sensitive and specific. GC and HPLC coupled with mass spectrometry or electrochemical detection are the most accurate and reproducible methods for a wide variety of analytes. Generally most methods, with the exception of immunoassay, have not been correlated with other methods. Recoveries from extraction methods, limits of detection, nature of compounds analysed and the internal standards used are summarised for more than 90 reports in the literature. From this data, it is clear that an inter-laboratory validation and correlation between a wide range of methods for phytoestrogen analysis is required. One underdeveloped area that requires particular attention is the analysis of plant lignans.

Time-resolved fluoroimmunoassay of plasma and urine O-desmethylangolensin

We present a method for the determination of the phytoestrogen metabolite O-desmethylangolensin (O-DMA) in plasma (serum) and in urine. O-DMA is a metabolite of daidzein, which occurs in soybeans. It has been suggested that isoflavones may afford protection against breast and prostate cancer and therefore, also the metabolites are of interest. The method is based on time-resolved fluoroimmunoassay (TR-FIA) using a europium chelate as a label. After the synthesis of 4"-O-carboxymethyl-O-DMA, this compound is coupled to bovine serum albumin, and then used as antigen in immunization of rabbits. The tracers with the europium chelate are synthesized using the same 4"-O-derivative of the alpha-methyldeoxybenzoin. After enzymatic hydrolysis and ether extraction the immunoassay is carried out by time resolved fluoroimmunoassay (TR-FIA). Cross-reactivity was tested with angolensin, dihydrogenistein, dihydrodaidzein, equol, 6'-OH-angolensin, trans-4-OH-equol, 6'-OH-O-DMA, cis-4-OH-equol and 5-OH-equol. The antiserum cross-reacted only with angolensin. This cross-reactivity seems not to influence the results, which were highly specific. Plasma samples are hydrolyzed and extracted. Urine samples are analyzed directly after hydrolysis without extraction. The correlation coefficient between the plasma TR-FIA results and the GC-MS results was high; r value was 0.985. The correlation coefficient between the urine TR-FIA results and the GC-MS results was high over the entire range of concentrations (0-1500 nmol/l); r value was 0.976, but lower in the low concentration range (0-100 nmol/l), i.e. value was 0.631. The intra-assay coefficients of variation (CVs) for plasma O-DMA concentrations and for urine O-DMA concentrations at three different concentrations varied 2.8-7.7 and 3.0-6.0%, respectively and the inter-assay CVs varied 3.8-8.9 and 4.4-6.6%, respectively. The working range of the plasma and urine O-DMA assays was 0.5-512 nmol/l.

Quantitative determination of estradiol fatty acid esters in human pregnancy serum and ovarian follicular fluid

BACKGROUND

Lipophilic estradiol derivatives carried by lipoprotein particles in blood may mediate antioxidant or endocrine effects. We developed a new quantitative method to determine the concentration of circulating lipophilic estradiol fatty acid esters in human early- and late-pregnancy serum and in ovarian follicular fluid.

METHODS

After extraction from serum or follicular fluid, estradiol fatty acid esters were separated from nonesterified estradiol by Sephadex LH-20 column chromatography. The estradiol ester fraction was hydrolyzed by saponification and further purified by several chromatographic steps. The hydrolyzed estradiol esters were measured by time-resolved fluoroimmunoassay.

RESULTS

The average estradiol fatty acid ester concentration in serum increased 10-fold during pregnancy, from 40.4 pmol/L (expressed as pmol/L estradiol; range, 25.0-64.2 pmol/L) in early pregnancy (n = 8) to 404 pmol/L (196-731 pmol/L) in late pregnancy (n = 10). The ratio of estradiol ester to nonesterified estradiol remained relatively constant during pregnancy, at 0.4-0.6%. In 10 follicular fluid samples, the mean estradiol ester concentration was 106 nmol/L (56.9-262 nmol/L). Compared with serum, a greater proportion of estradiol in follicular fluid (3.0-10%) was in the esterified form.

CONCLUSION

The new method provides a means to measure circulating estradiol fatty acid ester concentrations in human pregnancy serum.

In vitro metabolism of plant lignans: new precursors of mammalian lignans enterolactone and enterodiol

The metabolism of the plant lignans matairesinol, secoisolariciresinol, pinoresinol, syringaresinol, arctigenin, 7-hydroxymatairesinol, isolariciresinol, and lariciresinol by human fecal microflora was investigated to study their properties as mammalian lignan precursors. The quantitative analyses of lignan precursors and the mammalian lignans enterolactone and enterodiol were performed by HPLC with coulometric electrode array detector. The metabolic products, including mammalian lignans, were characterized as trimethylsilyl derivatives by gas chromatography-mass spectrometry. Matairesinol, secoisolariciresinol, lariciresinol, and pinoresinol were converted to mammalian lignans only. Several metabolites were isolated and tentatively identified as for syringaresinol and arctigenin in addition to the mammalian lignans. Metabolites of 7-hydroxymatairesinol were characterized as enterolactone and 7-hydroxyenterolactone by comparison with authentic reference compounds. A metabolic scheme describing the conversion of the most abundant new mammalian lignan precursors, pinoresinol and lariciresinol, is presented.

Accumulation of high-density lipoprotein-derived estradiol-17beta fatty acid esters in low-density lipoprotein particles

Estrogens are known to be powerful antioxidants in lipid-aqueous systems, as demonstrated by their inhibition of low-density lipoprotein (LDL) oxidation in vitro. Studies reporting that endogenous human estrogens could be rendered fat-soluble by esterification with fatty acids in vivo, and the subsequent detection of such esters in blood and fat tissue suggested a possible mechanism explaining how estrogens might protect LDL. Because of their lipophilicity, esterified estrogens may become incorporated in the lipoprotein structure, providing antioxidant potential for the particles. We incubated labeled 17beta-estradiol with ovarian follicular fluid and with plasma in the absence and presence of the LCAT inhibitor DTNB. This was followed by ultracentrifugal isolation of LDL and high-density lipoprotein and analysis of the radioactive label in the "ester" and "free" fractions purified from these lipoproteins. The results indicated that LCAT-mediated synthesis of esterified 17beta-estradiol occurred in high-density lipoprotein particles, and suggested a novel cholesterol ester transfer protein-mediated mechanism for their transfer to LDL particles.

Wheat bran and soy protein feeding do not alter urinary excretion of the isoflavan equol in premenopausal women

The capacity to convert the soy isoflavone daidzein to equol in vivo is presumably determined by an individual's intestinal microfloral populations; however, diet may also influence this conversion. The objectives of the present study were to determine whether a 1-mo supplementation of dietary fiber as wheat bran increases urinary equol excretion in equol excreters and stimulates equol production in nonexcreters and whether longer-term soy isoflavone intake increases equol production or alters overall urinary isoflavone excretion. First, we screened 74 women, ages 20-40 y, and determined their equol-excreter status. In these women, health and lifestyle patterns and habitual dietary intake did not differ according to equol-excreter status. Next, 26 of the women (13 equol excreters and 13 nonexcreters) were assigned (blocked on equol-excreter status) to either longer-term (1 mo) or short-term (4 d) soy protein supplementation. Within each soy treatment group, women participated in two 1-mo intervention periods (the exact length was determined by each woman's menstrual cycle) during which they consumed their usual diets supplemented daily with either 0 or 16 g dietary fiber in a randomized crossover design. A 1-mo washout period separated the two diet periods. Among the 19 women who completed both periods, fiber supplementation did not increase equol production in equol excreters or nonexcreters. In addition, isoflavonoid excretion did not differ by fiber dose or length of soy intervention. These results suggest that a daily 16 g-fiber dose as wheat bran and the addition of soy protein do not alter significantly the capacity of colonic microflora to produce equol.

Intestinal metabolism of rye lignans in pigs

To study the intestinal metabolism of lignans, the concentrations of plant and mammalian lignans in intestinal digesta sampled along the intestinal tract of pigs were determined by isotope dilution GC-MS. The pigs were fed rye-bread diets made from either whole rye-grains or rye-grain milling fractions enriched in pericarp-testa, aleurone or endosperm cells. The content and characteristics of dietary fibre varied between diets and had been shown to induce different colon fermentation patterns. As the metabolism of lignans depends on the action of the intestinal flora, we tested whether the rye-bread diets influence the metabolism of lignans. In the ileum, the lignans were mainly present as conjugated plant lignans, which were determined only when the analytical procedure included a hydrolysis step. High recovery of dietary lignans in the ileum may indicate that the lignans enter the enterohepatic circulation. In addition, two to three times the intake of lignans were recovered in the faeces when the diets had a high content of dietary fibre suggesting underestimation of plant lignans in the diet. Most of the plant lignans disappeared from the intestinal tract between the terminal ileum and the caecum. The intestinal concentrations and the disappearance of lignans correlated with the content of lignans in the diet, being highest on the pericarp-testa diet and lowest on the endosperm diet. No effect of fermentation pattern on the intestinal metabolism of lignans was observed. The lignans were liberated from the pericarp-testa diet although the plant cell walls remained largely undegraded.

Isoflavonoids and lignans have different potentials to modulate oxidative genetic damage in human colon cells

Polyphenolic compounds, including isoflavonoids and lignans, have been suggested to be chemopreventive on account of antioxidative properties. In this context it is of importance to have knowledge of their ability to reduce oxidative stress within target cells of tumorigenesis. Therefore, we investigated isoflavonoids and lignans for modulation of oxidative genetic damage in mammalian cells. H(2)O(2)-induced damage as well as endogenous DNA strand breaks and oxidized bases were determined after 30 min incubation of human colon cells with polyphenols using various modifications of the microgel electrophoresis assay (Comet assay). Enterolactone, a mammalian metabolite of plant lignans, was additionally investigated for modulation of intracellular oxidative stress in NIH 3T3 cells using laser scanning microscopy. In vivo effects of rye crispbread (a source of lignans) were investigated in 12 human volunteers by determining genetic damage in lymphocytes and antioxidant activity in plasma (FRAP assay). Genistein induced DNA breaks in the human tumour cell line HT29 clone 19A (12.5-100 microM). The polyphenols (100 microM) did not reduce damage induced by 150 microM H(2)O(2), indicating that they lacked antioxidative potential. At this concentration enterolactone also had no effect on intracellular oxidative stress induced by 31.25 and 125 microM H(2)O(2). In contrast, enterolactone, dihydrogenistein and formononetin reduced endogenous oxidative DNA damage at 100 microM. Daily ingestion of nine slices (76.5 g/day) of rye crispbread per day (containing 41.8 and 33.0 microg/100 g dry weight secoisolariciresinol and matairesinol, respectively) for 2 weeks did not significantly reduce genetic damage in blood lymphocytes, nor was there a modulation of plasma antioxidant capacity. The moderate effects of high concentrations of the tested compounds on endogenous oxidative DNA damage and failure to prevent H(2)O(2)- induced damage are indicative of only marginal protective potential by antioxidant mechanisms. The genotoxic effects of genistein deserve further investigation.

Time-resolved fluoroimmunoassay of plasma daidzein and genistein

We present a method for the determination of the phytoestrogens daidzein and genistein in plasma (serum). These weakly estrogenic isoflavones occur in soybeans and in smaller amounts in some other beans and plants. It has been suggested that they may afford protection against prostate and breast cancer. The method is based on time-resolved fluoroimmunoassay (TR-FIA) using a europium chelate as a label. After synthesis of 4'-O-carboxymethyl-daidzein and 4'-O-carboxymethyl-genistein the compounds are coupled to bovine serum albumin (BSA), then used as antigens to immunize rabbits. The tracers with the europium chelate are synthesized using the same 4'-O-derivative of the isoflavones. After enzymatic hydrolysis and ether extraction the immunoassay is carried out using the VICTOR 1420 multilabel counter (Wallac Oy, Turku, Finland). The antisera cross-reacted to some extent with some isoflavonoids but not with flavonoids. The cross-reactivity seems not to influence the results, which were highly specific for both compounds. The correlation coefficients between the TR-FIA methods and the reference method based on isotope dilution gas chromatography-mass spectrometry were high; r-values were about 0.95-0.99 depending on concentration. The intra-assay coefficients of variation (CV%) for daidzein and genistein at three different concentrations vary 3.2-4.5 and 3.2-4.1, respectively. The inter-assay CVs vary 5.0-6.3 and 4.5-5.3, respectively. The working ranges of the daidzein and genistein assays are 1.0-216 and 1.7-370 nmol/l, respectively. The plasma values (n = 80) of daidzein and genistein are very low in Finnish subjects (mean for daidzein, 3.8+/-6.8 and for genistein, 3.2+/-7.6 nmol/l; median value for daidzein 1.5 and for genistein 1.4 nmol/l).

Synthesis of C-C-bridged bis-isoflavones

Unique C-C-bridged bis-isoflavones 5, 8, and 9 were obtained by reaction of 2-bromomethyl-7,4'-dimethoxyisoflavone 4 with ethyl cyanoacetate anion or tetraethylammonium cyanide or by Pd-catalyzed ethoxycarbonylation, respectively. The phenolic carboxylic acid 7 is available from 5 in two steps.

Phyto-oestrogen content of berries, and plasma concentrations and urinary excretion of enterolactone after a single strawberry-meal in human subjects

Quantitative data on phyto-oestrogen, particularly lignan, content in edible plants are insufficient. We, therefore, measured isoflavonoids and lignans in nine edible berries using an isotope dilution gas chromatography-mass spectrometry method for foods and found substantial concentrations of the lignan secoisolariciresinol (1.39-37.18 mg/kg DM), low amounts of matairesinol (0-0.78 mg/kg DM) and no isoflavones. To determine pharmacokinetics and urinary excretion pattern of the mammalian lignan enterolactone derived from plant lignans, a study with human subjects was conducted. Five healthy women and two men consumed, after a 72 h period of a phyto-oestrogen-free regimen, a single strawberry-meal containing known amounts of plant lignans. Basal and post-meal blood and urine samples were collected at short intervals. The samples were analysed using time-resolved fluoroimmunoassay of enterolactone. The meal increased plasma concentration of enterolactone after 8-24 h and in urine in the 13-24 h and 25-36 h urine collections. High individual variability of the metabolic response was observed. Enterolactone excreted in the urine collected throughout the 48 h post-meal yielded on average 114% of the plant lignans consumed. It is concluded that berries containing relatively high concentrations of plant lignans contribute to plasma and urinary levels of mammalian enterolactone in human subjects.

Rapid analysis of phytoestrogens in human urine by time-resolved fluoroimmunoassay

A time-resolved fluoroimmunoassay (TR-FIA), with europium labeled phytoestrogens as tracers, was developed for the quantitative determination of enterolactone, genistein and daidzein in human urine. The aim was to create a method for the screening of large populations in order to assess the possible correlations between the urinary levels and the risk of Western diseases. After the synthesis of the 5'-carboxymethoxy derivative of enterolactone and 4'-O-carboxymethyl derivatives of daidzein and genistein, the respective compound was coupled to bovine serum albumin and then used as an antigen in the immunization of rabbits. The same derivatives of the phytoestrogen were used in preparing the europium tracers. After the enzymatic hydrolysis, the TR-FIA was carried out using the Victor 1420 multilabel counter. The method has sufficient sensitivity to measure the phytoestrogens at concentrations even below 5 nmol/l. The intra- and inter-assay coefficients of variation, at three different concentrations, varied from 1.9 to 5.3 and from 2.4 to 9.7, respectively. We measured urinary enterolactone, genistein and daidzein in 215 samples from Finnish healthy women and found that more than 50% of the values ranged between 1 and 7, <0.1 and 0.6 and below 0.6 micromol/24 h, respectively. The TR-FIA method including only a hydrolysis step gave higher values than those measured by gas chromatography-mass spectrometry (GC-MS). However, the assay results by the present method showed strong correlation with those obtained by GC-MS. It is concluded that the TR-FIA is suitable for population screening of urinary phytoestrogens.

Identification of isoflavone metabolites dihydrodaidzein, dihydrogenistein, 6'-OH-O-dma, and cis-4-OH-equol in human urine by gas chromatography-mass spectroscopy using authentic reference compounds

The metabolic products of daidzein and genistein, the principal isoflavones of soy, were examined. Six volunteers included soy into their normal diet for a 2-week period and urine samples were analyzed before and after soy consumption. Isolation and characterization of the urinary metabolites were carried out with absorption chromatography on Sephadex LH-20 and gas chromatography-electron ionization mass spectrometry (GC-EIMS). The structures of the isoflavones isolated were confirmed by using authentic reference compounds. Dihydrogenistein, 6'-OH-O-desmethylangolensin, and cis-4-OH-equol were identified, in addition to known isoflavonoids daidzein, genistein, glycitein, and the known metabolites equol, O-desmethylangolensin, and dihydrodaidzein, by comparing the retention times and the spectra of the urinary compounds with those of the synthesized reference standards. The mammalian lignans enterolactone and enterodiol were also identified. Derivatization of the isoflavones for GC-MS was examined by comparing two silylating reagents, N, O-bis-(trimethylsilyl)-trifluoroacetamide (BSTFA) and pyridine:hexamethyldisilazan:trimethylchlorosilane (QSM), both used for the derivatization of these compounds. The silylation experiments revealed significant differences in the compositions of the derivatization products. Some corrections were made concerning the earlier published data of dihydrogenistein and 6'-OH-O-dma.

Antioxidant protection of lipoproteins containing estrogens: in vitro evidence for low- and high-density lipoproteins as estrogen carriers

Some recent studies have reported that low-density lipoprotein (LDL) isolated from estrogen-treated postmenopausal women exhibited increased oxidation resistance ex vivo. However, the underlying mechanisms responsible for this effect are not clear. We explored the possibility that lipophilic derivatives of 17beta-estradiol (E(2)) could be incorporated into LDL and high-density lipoprotein (HDL) particles inhibiting lipoprotein oxidation. Introduction of small amounts of esterified E(2) into lipoproteins by means of incubation of free E(2) and E(2) 17-stearate in plasma did not result in any antioxidant effect. Using an artificial transfer system (Celite dispersion), larger amounts of E(2) esters could be incorporated into lipoproteins. Concentrations ranging between 0.27 and 1.38 molecules/LDL particle for E(2) 17-stearate and between 0.36 and 1.93 molecules/LDL particle for E(2) 17-oleate resulted in increased Cu(2+)-induced oxidation resistance of LDL as indicated by statistically significant lag time prolongations. Significant prolongations of lag times were also observed for HDL following incorporation of E(2) esters using Celite as transfer system. Our results suggest that free E(2) can be esterified and incorporated into lipoproteins during incubation in plasma. However, incorporation of supraphysiologic concentrations of E(2) esters into lipoproteins by means of the artificial transfer system was required in order to reduce their oxidation susceptibility.

Urinary isoflavonoid and lignan excretion on a Western diet: relation to soy, vegetable, and fruit intake

Dietary isoflavone and lignan phytoestrogens are potential chemopreventive agents. This has led to a need to monitor exposure to these compounds in human populations and to determine which components of a mixed diet contribute to the exposure. Typically, urinary isoflavonoid excretion is associated with soy consumption and that of lignans is associated with whole grains. However, other plant foods are known to contain phytoestrogen precursors. The purpose of this study was to examine the association between urinary isoflavonoid and lignan excretion and intakes of vegetables and fruits (V&F). Isoflavonoids (genistein, daidzein, O-desmethylangolensin, and equol) and lignans (enterolactone, enterodiol, and matairesinol) were measured in urine collected for 3 days from 49 male and 49 female volunteers (age, 18-37 years) reporting a wide range of habitual V&F intakes. Dietary intakes were assessed using 5-day diet records and a food frequency questionnaire. V&F groupings (total V&F, total V, total F, soyfoods, and V&F grouped by botanical families) were used to assess the relationship between V&F intake and urinary isoflavonoid and lignan excretion. Pearson correlations were performed. Intake of soyfoods was correlated significantly with urinary genistein (r = 0.40; P = 0.0001), O-desmethylangolensin (r = 0.37; P = 0.0002), daidzein (r = 034; P = 0.0007), and the sum of isoflavonoids (r = 0.39; P = 0.0001). There was no association between equol excretion and soy intake or between the isoflavonoids and any other V&F groupings. In addition, isoflavonoid excretion was correlated positively with intake of high-fat and processed meats, particularly among men who did not consume soy. This suggests that, even in the United States, on a Western diet, soyfoods are the primary contributors to isoflavone intake; however, additional "hidden sources" of soy may also contribute to exposure. In contrast, a variety of fiber-containing foods contributed to lignan excretion; the sum of the urinary lignans, enterodiol, enterolactone, and matairesinol, was associated with intake of total F (r = 0.27; P = 0.008), total V&F (r = 0.25; P = 0.01), soyfoods (r = 0.28; P = 0.006), and dietary fiber (r = 0.36; P = 0.0003). Overall, urinary phytoestrogens (isoflavonoids + lignans) were significantly higher in "high" compared with "low" V&F consumers. Compared with the "low" V&F group, the "high" group consumed diets that were, on average, higher in fiber and carbohydrate and soyfoods and lower in fat; thus, the urinary phytoestrogens may also be a useful marker of healthier dietary patterns.

Incorporation of esterified soybean isoflavones with antioxidant activity into low density lipoprotein

We have recently reported that dietary intake of soybean isoflavone phytoestrogens resulted in increased oxidation resistance of isolated low density lipoprotein (LDL). In order to explore the underlying mechanisms we designed two types of in vitro experiments. First, we prepared several different isoflavone fatty acid esters to increase their lipid solubility and studied their incorporation into LDL. Second, the oxidation resistance of the isoflavone-containing LDLs was investigated with Esterbauer's 'conjugated diene' method using Cu2+ as prooxidant. Unesterified daidzein and genistein as well as genistein stearic acid esters were incorporated into LDL to a relatively small extent (0.33 molecules per LDL particle, or less) and they did not significantly influence oxidation resistance. The oleic acid esters of isoflavones were incorporated more effectively, reaching a level of 2.19 molecules per LDL particle or more, and the 4',7-O-dioleates of daidzein and genistein exhibited prolongations of lag times by 46% (P<0.05) and 202% (P<0.01), respectively. A smaller but significant increase in lag time (20.5%, P<0.01) was caused by daidzein 7-mono-oleate. In summary, esterification of soybean isoflavones daidzein and genistein with fatty acids at different hydroxyl groups provided lipophilicity needed for incorporation into LDL. Some isoflavone oleic acid esters increased oxidation resistance of LDL following their incorporation.

Maternal and neonatal phytoestrogens in Japanese women during birth

OBJECTIVE

High levels of soy isoflavonoids among adult Japanese persons are associated with a low incidence of hormone-dependent cancers, but nothing is known about isoflavonoids in pregnancy.

STUDY DESIGN

We studied 7 young healthy Japanese women at delivery by measuring 6 phytoestrogen metabolites in maternal and cord plasma and in amniotic fluid.

RESULTS

Total maternal plasma isoflavonoid concentrations ranged from 19 to 744 nmol/L (mean 232 nmol/L), cord plasma values ranged from 58 to 831 nmol/L (mean 299 nmol/L), and amniotic fluid values ranged from 52 to 779 nmol/L (mean 223 nmol/L). Maternal and cord plasma and amniotic fluid lignan values were low.

CONCLUSIONS

The high levels of isoflavonoid phytoestrogens found in healthy neonatal Japanese infants indicate transfer of isoflavonoids from the maternal to the fetal compartment. These compounds may modify estrogen metabolism and action during fetal life and perhaps affect cancer risk.

Antiproliferative efficacy of lipophilic soy isoflavone phytoestrogens delivered by low density lipoprotein particles into cultured U937 cells

Some fat-soluble bioactive substances incorporated into low density lipoprotein (LDL) may be delivered into cells via LDL receptor pathway influencing cellular functions. In this study, we synthesized a number of fat-soluble isoflavone esters and investigated their incorporation into LDL as well as their delivery into U937 cells. Using an artificial transfer system (Celite dispersion), genistein and daidzein oleates and daidzein dilinoleate were efficiently incorporated into LDL with concentrations ranging between 2.7 to 16.9 isoflavone molecules/LDL particle, while much smaller amounts of unesterified isoflavones and genistein stearates were transferred into LDL. LDL containing 7-oleates or 4',7-dioleates of genistein and daidzein significantly reduced U937 cell proliferation by 36-43%. The strongest inhibitory effect was shown by daidzein 4',7-dilinoleate with 93% reduction of cell proliferation. Neither of the 4'-oleates of genistein and daidzein contained in LDLs exhibited antiproliferative effects although they were incorporated into LDL. In summary, we demonstrated that isoflavones made fat-soluble by esterification can be incorporated into LDL in vitro and delivered into cultured U937 cells via the LDL-receptor pathway, reducing the cell proliferation.

Time-resolved fluoroimmunoassay for plasma enterolactone

We present a method for the determination of the lignan enterolactone in plasma (serum). This compound, produced by intestinal bacteria from matairesinol and secoisolariciresinol in fiber-rich food, is a biomarker related to the intake of a healthy diet. The method is based on time-resolved fluoroimmunoassay using a europium chelate as a label. After synthesis of 5'-O-carboxymethoxyenterolactone the compound is coupled to bovine serum albumin and then used as antigen in immunization of rabbits. The tracer with the europium chelate is synthesized using the same 5'-derivative of enterolactone. After enzymatic hydrolysis and ether extraction the immunoassay is carried out using the VICTOR 1420 multilabel counter (Wallac Oy, Turku, Finland). No antiserum cross-reactivity with available lignans, isoflavonoids, or flavonoids could be detected. The intraassay and interassay coefficients of variation at different concentrations vary 4.6-6.0 and 5.5-9.9, respectively. The working range of the assay is 1.5-540 nmol/liter. We measured enterolactone in serum/plasma of 224 Finnish subjects: 98.8% of the subjects had values <100 nmol/liter, 38.0% had 20-39.9 nmol/liter, and 34.4% had <20 nmol/liter.

Phytoestrogens and inhibition of angiogenesis

The consumption of a plant-based diet can prevent the development and progression of chronic diseases associated with extensive neovascularization, including the progression and growth of solid malignant tumours. We have previously shown that the plant-derived isoflavonoid genistein is a potent inhibitor of cell proliferation and in vitro angiogenesis. Moreover, the concentration of genistein in the urine of subjects consuming a plant-based diet is 30-fold higher than that in subjects consuming a traditional Western diet. We have also reported that certain structurally related flavonoids are more potent inhibitors than genistein. Indeed, 3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, apigenin and luteolin inhibit the proliferation of normal and tumour cells as well as in vitro angiogenesis at half-maximal concentrations in the lower micromolar range. The wide distribution of isoflavonoids and flavonoids in the plant kingdom, together with their anti-angiogenic and anti-mitotic properties, suggest that these phytoestrogens may contribute to the preventive effect of a plant-based diet on chronic diseases, including solid tumours.

Pharmacokinetics of soybean isoflavones in plasma, urine and feces of men after ingestion of 60 g baked soybean powder (kinako)

To take advantage of the various pharmacologic activities of soy bean isoflavones, more detailed studies of the absorption and excretion rates of these compounds in humans and subsequent evaluation of their bioavailabilities are required. We conducted a pharmacokinetic study of soybean isoflavones in seven healthy male volunteers. After ingestion of 60 g of kinako (baked soybean powder, containing 103 micromol daidzein and 112 micromol genistein), changes of the isoflavone and metabolite concentrations in plasma, urine and feces were measured by gas chromatography-mass spectrometry. The plasma concentration of genistein increased after 2 h and reached its highest value of 2.44 +/- 0.65 micromol/L 6 h later. The plasma concentration of daidzein peaked at 1.56 +/- 0.34 micromol/L at the same time, but it was always lower than that of genistein. Peak plasma concentration of O-desmethylangolensin (O-DMA) and equol appeared after the daidzein peak in four and two subjects, respectively. In contrast with plasma, daidzein was the main component in urine. Urinary daidzein excretion started to increase shortly after the rise in its plasma concentration and reached 2.4 micromol/h 8 h after ingestion of kinako. Genistein excretion in urine paralleled that of daidzein, but the value at 6 h was about half (1.1 micromol/h). The majority of ingested isoflavones after ingestion of kinako were recovered on d 2 or 3 in the feces. Total recovery of daidzein, O-DMA and equol from urine and feces was 54.7%, calculated from daidzein intake; 20.1% of administered genistein was recovered as genistein. The half-lives of plasma genistein and daidzein were 8.36 and 5.79 h, respectively. The individual plasma and urinary concentrations of equol and O-DMA were quite variable; subjects were classified as high and low metabolizers. The high plasma concentration of isoflavones for at least several hours after a single ingestion of soy protein suggests that these compounds may interact with macromolecules and have biological effects.

Effect of soybean phytoestrogen intake on low density lipoprotein oxidation resistance

The oxidation of low density lipoproteins (LDLs) is thought to take place in the arterial intima when the particles have become isolated from circulating water-soluble antioxidants. We hypothesized that isoflavonoid antioxidants derived from soy could be incorporated into lipoproteins and possibly could protect them against oxidation, which is regarded as atherogenic. Six healthy volunteers received 3 soy bars [containing the isoflavonoid antioxidants genistein (12 mg) and daidzein (7 mg)] daily for 2 weeks. LDLs were isolated from blood drawn at the the end of a 2-week dietary baseline period, after 2 weeks on soy, and after discontinuation of soy. Large increases in plasma isoflavonoid levels occurred during soy feeding, but only minute amounts were stably associated with lipoproteins (less than 1% of plasma isoflavonoids in the LDL fraction). The LDLs were subjected to copper-mediated oxidation in vitro. Compared with off soy values, lag phases of LDL oxidation curves were prolonged by a mean of 20 min (P < 0.02) during soy intake, indicating a reduced susceptibility to oxidation. The results suggest that intake of soy-derived antioxidants, such as genistein and daidzein, may provide protection against oxidative modification of LDL. As only very small amounts of these substances were detected in purified LDL, modified LDL particles may have been produced in vivo by circulating isoflavonoids promoting resistance to oxidation ex vivo.

Radioimmunoassay of free genistein in human serum

Two radioimmunoassay (RIA) systems for genistein have been established, based on polyclonal antibodies against genistein-4'-O-(carboxymethyl)ether-bovine serum albumin and genistein-7-O-(carboxymethyl)ether-bovine serum albumin conjugates. The sensitivities of assays were 4.44 and 10.4 fmol (1.2 and 2.8 pg)/tube, respectively, the intraassay coefficients of variation ranged from 3.54 to 9.30%, the interassay C.V. varied from 6.72 to 19.7%, depending on the type of method and on genistein concentration. The cross-reactivities with other chemically related compounds (with exception of genistein derivatives at the position used for construction of the immunogen) were 5.5 and 6.1% for daidzein and 3.9 and 0.04% for formononetin in RIAs using reagents prepared through positions 4'- and 7- of genistein, respectively. The method was used for measurement of genistein levels in 26 omnivore subjects and in three volunteers after consumption of a meal prepared from 125 g of cooked whole soybeans. The values obtained in ether extracts from human sera were almost identical for both RIA systems, indicating that both RIAs measure the same entity.

Synthesis of novel mammalian metabolites of the isoflavonoid phytoestrogens daidzein and genistein

The synthesis of novel mammalian metabolites of dietary isoflavones, dihydrodaidzein (4',7-dihydroxyisoflavanone) 7, dihydrogenistein (4',5,7-trihydroxyisoflavanone) 9, 6'-hydroxy-O-demethylangolensin [1-(2,4,6-trihydroxyphenyl)-2-(4-hydroxyphenyl)propan-1-one] 10, and cis- and trans-4',7-dihydroxyisoflavan-4-ols 11, 12 is described, and their characteristics by physical and chemical constants given for the first time.

Lignan and isoflavonoid concentrations in tea and coffee

Tea is a beverage consumed widely throughout the world. The existence in tea of chemopreventing compounds possessing antimutagenic, anticarcinogenic and antioxidative properties has been reported. High intakes of tea and foods containing flavonoids have recently been shown to be negatively correlated to the occurrence of CHD. However, tea may contain other compounds with similar activities. Using a new gas chromatographic-mass spectrometric method we measured lignans and isoflavonoids in samples of twenty commercial teas (black, green and red varieties) and, for comparison, six coffees. Both unbrewed and brewed tea were investigated. The analysis of the teas yielded relatively high levels of the lignans secoisolariciresinol (5.6-28.9 mg/kg; 15.9-81.9 mumol/kg) and matairesinol (0.56-4.13 mg/kg; 1.6-11.5 mumol/kg) but only low levels of isoflavonoids. Because the plant lignans, as well as their mammalian metabolites enterolactone and enterodiol, have antioxidative properties and these mammalian lignans occur in high concentrations in plasma, we hypothesize that lignan polyphenols may contribute to the protective effect of tea on CHD.

Identification of isoflavonoids in beer

The isoflavonoids, genistein (4',5,7-trihydroxyisoflavone), biochanin A (5,7-dihydroxy-4'-methoxyisoflavone), daidzein (4',7-dihydroxyisoflavone), and formononetin (7-hydroxy-4'-methoxyisoflavone) are supposed to be health-promoting dietary factors of plant origin. They are particularly abundant in seeds and other parts of many plant species belonging to Leguminosae. The most popular source of isoflavonoids in human diet is soy. Here, evidence is presented that isoflavonoids are regularly found in beer. Diethyl ether extracts of beer were fractionated on thin-layer chromatography-silica, (straight phase) and rechromatographed using a reversed phase high-performance liquid chromatography octadecylsilica column. The fractions were analyzed by two recently developed radioimmunoassays, the first of them being specific for diadzein/formononetin and the second one specific for genistein/biochanin A. The immunoreactivity was found only in fractions with the mobility corresponding to the positions of standards on control chromatograms. Additionally, 26 samples of bottled beer were analyzed for isoflavonoid content using the combination of reversed phase high-performance liquid chromatography and radioimmunoassay. The sum of the four isoflavonoids ranged from 1.26 to 29 nmol/L in individual beers. Formononetin was the major isoflavonoid (0.19-14.99 nmol/L), whereas the concentration of daidzein was several times lower (0.08-2.5 nmol/L). Genistein and biochanin A concentrations were comparable, ranging from 0.169-6.74 nmol/L and from 0.820-4.84 nmol/L for genistein and biochanin A, respectively. It is concluded that beer contains significant amounts of biologically active isoflavonoid phytoestrogens.

2,6-Bis((3,4-dihydroxyphenyl)-methylene)cyclohexanone (BDHPC)-induced apoptosis and p53-independent growth inhibition: synergism with genistein

Estrogen binds to two classes of proteins in the cells, the high-affinity estrogen receptor (ER) as well as a low affinity estrogen type II binding site (EBS-II). Methyl p-hydroxyphenyllactate (MeHPLA) is an endogenous ligand for EBS-II. Binding of MeHPLA to EBS-II has a growth regulatory effect in estrogen-responsive cells, and levels of MeHPLA are decreased in breast cancer due to degradation by a specific esterase. 2,6-bis((3, 4-dihydroxyphenyl)-methylene) cyclohexanone (BDHPC) is an esterase-resistant analogue of MeHPLA which binds irreversibly to EBS-II and inhibits growth of breast cancer cells. In the present study, we analyzed the mechanism of growth inhibition by BDHPC. Treatment with BDHPC resulted in accumulation of cells in G1 phase and apoptosis. The G1 accumulation was not dependent on a functional p53 gene. The G1-specific growth inhibition by BDHPC was found to act synergistically with the G2/M-specific inhibition induced by the tyrosine kinase inhibitor genistein, suggesting this drug combination could be effectively used in cancer treatment.

Flavonoids, dietary-derived inhibitors of cell proliferation and in vitro angiogenesis

Consumption of a plant-based diet can prevent the development and progression of chronic diseases associated with extensive neovascularization, including solid malignant tumors. In previous studies, we have shown that the plant-derived isoflavonoid genistein is a potent inhibitor of cell proliferation and in vitro angiogenesis. In the present study, we report that certain structurally related flavonoids are more potent inhibitors than genistein. Indeed, 3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, apigenin, and luteolin inhibited the proliferation of normal and tumor cells, as well as in vitro angiogenesis, at half-maximal concentrations in the low micromolar range. We have previously demonstrated that genistein concentrations in the urine of subjects consuming a plant-based diet is 30-fold higher than in subjects consuming a traditional Western diet. The wider distribution and the more abundant presence of flavonoids in the plant kingdom, together with the present results, suggest that flavonoids may contribute to the preventive effect of a plant-based diet on chronic diseases, including solid tumors.

A novel radioimmunoassay for daidzein

A radioimmunoassay for daidzein was established, based on polyclonal antibodies against daidzein-4'-O-(carboxymethyl)ether-BSA. The sensitivity of the assay was 0.4 pg/tube; the intra- and interassay coefficients of variation varied from 4.1 to 11.5% and from 5.6 to 21.7%, respectively, depending upon the method (direct or extraction) and concentration of daidzein in the sample. The cross reactivities with other chemically related compounds, with the exception of 4'-derivatives of daidzein, were 2.4% for dihydrodaidzein, 1.3% for genistein, 1.5% for biochanin A, and 1.6% for equol, respectively. The method was used for measurement of daidzein levels in 105 normal human subjects and in three volunteers after consumption of a meal prepared from 125 g of cooked whole soybeans. The daidzein values obtained following diethyl ether extraction of human sera was only 8% of that obtained by direct radioimmunoassay. We suggest that this difference is caused by cross-reacting daidzein 4'-glucuronides and -sulfates present in serum. Using ether extraction, the basal serum levels of free daidzein were 0.11 ng/mL (0.43 nmol/L), with 14 subjects showing no detectable levels. Levels were detectable in all subjects with the direct assay with a mean value of 7.1 ng/mL (28.0 nmol/L). Peak levels were reached 4 hours after ingestion of the soybeans. The levels were 10.3 +/- 3.6 ng/mL (40.4 +/- 14.3 nmol/L) for free daidzein and 129.4 +/- 36.1 ng/mL (509 +/- 142 nmol/L) for total immunoreactive compounds. After 24 hours, the levels were still clearly distinguishable from the basal levels; the concentrations were 0.43 +/- 0.15 ng/mL (1.69 +/- 0.59 nmol/L) and 24.36 +/- 6.07 ng/mL (95.9 +/- 23.9) for free and total immunoreactive material, respectively. It is concluded that this is the first immunoassay for a phytoestrogen in human biological fluids, and for the first time serial assays of unconjugated daidzein in plasma have been possible.

A soy protein isolate rich in genistein and daidzein and its effects on plasma isoflavone concentrations, platelet aggregation, blood lipids and fatty acid composition of plasma phospholipid in normal men

The effects of consuming a soy protein isolate beverage powder (60 g/d for 28 d) vs. a casein supplement was evaluated in 20 male subjects who were randomly allocated into the two groups. A dramatic rise in plasma isoflavone concentrations was observed after supplementation in the soy protein group, the levels reaching 907 +/- 245 nmol/L for genistein (a 110-fold increase) and 498 +/- 102 nmol/L for daidzein (a 150-fold increase) as measured by isotope dilution gas chromatography - mass spectrometry. These concentrations are higher than previously reported for the plasma of Japanese subjects consuming a traditional diet (276 nmol/L and 107 nmol/L, respectively). No significant differences in collagen- or 9,11-dideoxy-11alpha, 9alpha-epoxymethanoprostaglandin F2alpha (U46619)-induced platelet aggregation were observed in platelet-rich plasma from the two groups; the increase in plasma isoflavonoids from soy protein supplementation is not sufficient to significantly inhibit platelet aggregation ex vivo. Similarly, plasma total and HDL-cholesterol were not affected by protein supplementation, possibly because the men were normocholesterolemic at entry. Analysis of plasma phospholipid polyunsaturated fatty acid composition showed no differences between soy protein and casein supplementation. Previous investigations reported a significant alteration in fatty acid status in animals fed soy protein relative to those fed casein. The present studies indicate that although soy protein supplementation to a typical Western diet can increase plasma concentrations of isoflavones, this may not necessarily be sufficient to counter heart disease risk factors such as high plasma cholesterol and platelet aggregation.

Isotope dilution gas chromatographic-mass spectrometric method for the determination of isoflavonoids, coumestrol, and lignans in food samples

We present a method for the quantitative determination of the phytoestrogens formononetin, biochanin A, daidzein, genistein, and coumestrol and simultaneously the lignans secoisolariciresinol (SECO) and matairesinol in plant-derived foods. These compounds are measured by isotope dilution gas chromatography-mass spectrometry in the selected ion monitoring mode (ID/GC/MS/SIM) using synthesized deuterated internal standards for the correction of losses during the procedure. A three-step hydrolysis--a rehydration with distilled H2O, followed by enzymatic and acid hydrolysis--has been applied in order to convert the diphenolic glycosides into their respective aglycones. Purification and separation are carried out in two ion-exchange chromatographic steps followed by derivatization and GC-MS. The within-assay imprecision values vary 3.1-9.6% and the between-assay imprecision 7.0-21.2%. The mean recovery of authentic standards processed through the whole procedure varied from 95.5 to 105.5%. Values for some different food samples are presented. The simultaneous determination of the biologically most interesting phytoestrogens and lignans in foods has not been carried out previously and the method will be useful for screening of important foods in populations with different risk of cancer and coronary heart disease, and for metabolic studies.

Effect of diet on lignans and isoflavonoid phytoestrogens in chimpanzees

Diphenolic compounds belonging to the classes of lignans and isoflavonoids have been identified in urine of man and animals, including the chimpanzee. Some of these compounds, formed by intestinal bacteria from plant lignans and phytoestrogens, have been shown in animal studies to exhibit biological activities that suggest they could function as cancer-protective compounds. The effect of diet on urinary excretion of these compounds in the adult male chimpanzee has been studied. It was found that the chimpanzees consuming their regular food excreted large amounts of the isoflavonoid phytoestrogens, equol (mean +/- SE) (127.5 +/- 34.0 nmol/mg cr.) and daidzein (20.7 +/- 9.0 nmol/mg cr.) and the lignan, enterolactone (14.1 + 3.5 nmol/mg cr.). Small amounts of the lignan, enterodiol, (0.4 +/- 0.2 nmol/mg cr.) were also excreted. On all other four test diets (high protein, high carbohydrate, high vegetable, and high fat), the excretion was less, particularly on a high fat diet where the excretion of all diphenolic compounds was reduced by more than 90% to a level observed in omnivorous human subjects or women with breast cancer. These results suggest that diet profoundly influences the excretion of both animal lignans and phytoestrogens in urine. Because non-human primates are particularly resistant to mammary and genital carcinoma on estrogen treatment, the present data suggest that the very high levels of phytoestrogens and lignans as found during exposure to the regular diet may partially account for why these primates are so resistant to hormonal manipulations to induce cancer.

Isotope dilution gas chromatographic-mass spectrometric method for the determination of unconjugated lignans and isoflavonoids in human feces, with preliminary results in omnivorous and vegetarian women

We describe an isotope dilution gas chromatographic-mass spectrometric (GC/MS) method for the identification and quantitative determination of the lignans enterolactone, enterodiol, and matairesinol and the isoflavonoids daidzein, equol, O-desmethylangolensin, and genistein in feces. Following the addition of deuterated internal standards for all compounds, the feces samples are extracted and purified in several ion exchange chromatographic steps. Following formation of trimethylsilyl ethers, the samples are analyzed by combined capillary column GC/MS in the selective ion monitoring mode and corrected for all losses during the procedure using the deuterated internal standards. Results on the reliability of the method and values for nine Finnish omnivorous and nine vegetarian women are presented.

Lignan and isoflavonoid conjugates in human urine

Lignans and isoflavonoids are two groups of diphenolic phytoestrogens of plant origin which have gained increasing interest because of their possible cancer protective properties. High excretion of these compounds occur in populations at low risk of breast, prostate and colon cancer consuming either high amounts of whole-grain (lignans and some isoflavonoids) or soy products (isoflavonoids and some lignans). We determined the pattern of conjugation of the phytoestrogens in four urine samples from vegetarian or semivegetarian women and in two samples from men. Seven compounds were investigated: enterodiol, enterolactone, matairesinol, diadzein, equol, genistein and O-desmethylangolensin. The fractions quantified are the free fraction, mono- and disulfate, as well as the mono-, di- and sulfoglucuronide fractions. For the fractionation and purification we used ion-exchange chromatography and the determination of the concentrations of each compound in all fractions was done by isotope dilution gas chromatography-mass spectrometry (GLC-MS) using deuterated internal standards of all diphenols. More than 60% of all compounds determined, occurred in the monoglucuronide fraction. Daidzein, enterodiol and equol are excreted to a relatively high extent as sulfoglucuronides and genistein as diglucuronide. We conclude that the general pattern of lignan and isoflavonoid conjugates in urine is similar to that of endogenous estrogens.

Phytoestrogen content and estrogenic effect of legume fodder

This study is a summary of Finnish investigations of the phytoestrogen content of legume plants, red clover, white clover, alfalfa, and goat's rue. In addition to the chemical analyses, biological studies were performed. Uterine weight of immature rats was used as an indicator of the estrogenic effect of the fodder used. All red clover varieties studied contained estrogenic isoflavones, especially formononetin and biochanin-A. The phytoestrogen content varied from 1.0% to 2.5% of dry matter. The biological study of white clover showed a clear estrogenic effect not visible through chemical analysis. Alfalfa contains small quantities of formononetin and biochanin-A, but 25-65 ppm coumestrol in dry matter. The estrogenic effect of alfalfa was obvious in the biological study. Goat's rue did not contain any known phytoestrogens, and the biological study was completely negative.

Synthesis and labeling of isoflavone phytoestrogens, including daidzein and genistein

The synthesis of the important diphenolic isoflavone type phytoestrogens starting from the corresponding unprotected phenols and arylacetic acids is discussed. The aryl rings may carry additional alkyl, methoxy, and/or halogeno groups. Intermediate polyhydroxy deoxybenzoins can also be isolated in good yield. Isotopically labeled isoflavone phytoestrogens were prepared for use as internal standards in ion exchange chromatography and GC-MS selected ion monitoring (SIM technique). Traditional methods rely on total synthesis using deuterated starting materials for the preparation of labeled isoflavonoid structures. We have used successfully an application where the H/D exchange is performed within the finished molecular framework, based on the exchange of aromatic protons that are ortho or para to a phenolic OH group. By this method the deuterated products are available in an isotopic purity of 90% or higher.

Inhibition of human aromatase by mammalian lignans and isoflavonoid phytoestrogens

Isoflavonoid phytoestrogens and lignans in plants are known to be constituents of animal and human food and recently they have been found in human urine and other biological materials. These compounds have received increasing attention because of their interesting biological properties and possible role in human cancer and other diseases. The present study demonstrates that the main mammalian lignan enterolactone (trans-2,3-bis[(3-hydroxyphenyl)methyl]-butyrolactone) and some other diphenols are moderate or weak inhibitors of human estrogen synthetase (aromatase) and that this lignan binds to or near the substrate region of the active site of the P-450 enzyme. The inhibition is competitive with respect to testosterone and androstenedione, and the lignan affinity is 1/75-1/300 that of these natural substrates. It is suggested that the high concentration of lignans in vegetarians, by inhibiting aromatase in peripheral and/or cancer cells and lowering estrogen levels, may play a protective role as antipromotional compounds during growth of estrogen-dependent cancers.

Quantitative determination of lignans and isoflavonoids in plasma of omnivorous and vegetarian women by isotope dilution gas chromatography-mass spectrometry

The first quantitative method for the determination of both lignans and isoflavonoid phytoestrogens in plasma is presented. Using ion-exchange chromatography the diphenols are separated into two fractions 1) the biologically "active" fraction containing the free compounds + mono- and disulfates and 2) the biologically "inactive" fraction containing the mono- and diglucuronides and the sulfoglucuronides. After hydrolysis the fractions are further purified by solid phase extraction and ion exchange chromatography. Losses during the complete procedure are corrected for using radioactive estrogen conjugates during the first steps and later by adding deuterated internal standards of all compounds measured (matairesinol, enterodiol, enterolactone, daidzein, O-desmethylangolensin, equol, and genistein). The final determination is carried out by isotope dilution gas chromatography-mass spectrometry in the selected ion monitoring mode (GC/MS/SIM). The diphenols may be measured at concentrations as low as 0.2 to 1.0 nmol/l. Results of plasma analyses of all compounds in 27 pre- and postmenopausal omnivorous and vegetarian women are presented for the first time. The most important findings are that the free+sulfate fraction is low for genistein (3.8% of total), but as much as 21-25% of enterolactone and enterodiol occurs in this fraction. A good correlation between plasma and urine values was found. Total concentrations of individual compounds vary greatly between the subjects (from pmol/l to mumol/l), the vegetarians having higher values, particularly one vegan subject. The highest total enterolactone concentration value exceeded 1 mumol/l. It is concluded that a highly specific method for the assay of 3 lignans and 4 isoflavonoids in plasma has been developed. This method will be useful in future studies of lignan and isoflavonoid metabolism.

Identification in human urine of a natural growth inhibitor for cells derived from solid paediatric tumours

Partially purified urine of healthy human subjects contains several fractions able to inhibit the proliferation of cultured human neuroblastoma cells. One of the most active fractions was further analysed by gas chromatography-mass spectrometry and shown to contain genistein, a substance formed in the human body from precursors obtained by diet. Synthetic genistein was able to inhibit the proliferation of human neuroblastoma cells with a half-maximal effect at 5-10 mumol l-1 concentrations. Genistein displayed similar potencies in inhibiting the proliferation of cells derived from various other solid pediatric tumours. Our results suggest that genistein is a natural antineoplastic agent present in diet and that it could be useful for the therapy of paediatric tumours.

Dietary phytoestrogens and cancer: in vitro and in vivo studies

Thirty postmenopausal women (11 omnivores, 10 vegetarians and 9 apparently healthy women with surgically removed breast cancer) were investigated with regard to the association of their urinary excretion of estrogens, lignans and isoflavonoids (all diphenols) with plasma sex hormone binding globulin (SHBG). A statistically significant positive correlation between urinary total diphenol excretion and plasma SHBG was found which remained statistically significant after elimination of the confounding effect of body mass determined by body mass index (BMI). Furthermore we found a statistically significant negative correlation between plasma SHBG and urinary excretion of 16 alpha-hydroxyestrone and estriol which also remained significant after eliminating the effect of BMI. Furthermore we observed that enterolactone (Enl) stimulates the synthesis of SHBG by HepG2 liver cancer cells in culture acting synergistically with estradiol and at physiological concentrations. Enl was rapidly conjugated by the liver cells, mainly to its monosulfate. Several lignans and the isoflavonoids daidzein and equol were found to compete with estradiol for binding to the rat uterine type II estrogen binding site (the s.c. bioflavonoid receptor). It is suggested that lignans and isoflavonoids may affect uptake and metabolism of sex hormones by participating in the regulation of plasma SHBG levels and in this way influence their biological activity and that they may inhibit cancer cell growth like some flavonoids by competing with estradiol for the type II estrogen binding sites.

Phytoestrogens: new ligands for rat and human alpha-fetoprotein

The binding of the lignans, enterolactone, enterodiol, nordihydroguaiaretic acid (NDGA), and the isoflavonic phytoestrogen equol, to human and rat alpha-fetoprotein (AFP) was studied. They had differential inhibitory effects (NDGA greater than equol greater than enterolactone greater than enterodiol) on the binding of estrone and estradiol to rat AFP and the binding of unsaturated fatty acid to both rat and human AFP. Inhibition was dose-dependent. The apparent dissociation constants (Kd) for phytoestrogens binding to AFP were: Kd NDGA = 5 +/- 1.2.10(-7) M, Kd equol = 6.7 +/- 0.8.10(-6) M, Kd enterolactone = 1.7 +/- 0.4.10(-5) M and Kd enterodiol = 2.2 +/- 0.6.10(-5) M. The Kd for estrone binding to rat AFP was increased by increasing concentrations of equol, but the number of esterone binding sites remained unchanged. This, plus the results of double-reciprocal plots, suggests that they compete for the same site(s). NDGA also competitively inhibited estrone binding at low NDGA concentrations (increased Kd), but high concentrations induced conformational changes in rat AFP, as both Kd and the number of binding sites (n) were altered. Both rat and human AFPs underwent changes in electrophoretic behaviour and loss of immunoreactivity with increasing NDGA, suggesting that NDGA binding induces conformational changes in the AFPs. However, equol did not alter the electrophoretic or immunological properties of either rat or human AFP, providing further evidence for qualitative differences in the effects of these diphenols. These findings indicate that phytoestrogens could play a role in AFP-dependent normal and pathological growth and development.

Isotope dilution gas chromatographic-mass spectrometric method for the determination of lignans and isoflavonoids in human urine, including identification of genistein

We describe an isotope dilution gas chromatographic-mass spectrometric method for the quantitative determination of the lignans enterolactone, enterodiol and matairesinol and the isoflavonoids daidzein, equol, O-desmethylangolensin and genistein in urine. Furthermore we present the gas chromatographic/mass spectrometer identification of genistein. Urine samples were extracted on Sep-Pak cartridges, conjugated fractions were isolated by chromatography on the acetate form of DEAE-Sephadex and deuterated internal standards of all seven compounds were added to the samples before hydrolysis. The hydrolysate was extracted on a Sep-Pak cartridge and following chromatography on the acetate form of QAE-Sephadex two fractions were obtained: Fraction 1 contained equol, enterolactone, enterodiol, matairesinol and all estrogens and fraction 2 contained O-desmethylangolensin, daidzein and genistein. The latter was ready for gas chromatography/mass spectrometry, but the first one was further purified to eliminate the estrogens by chromatography on the carbonate form of QAE-Sephadex. Following silylation, the samples were analyzed by combined capillary column gas chromatography/mass spectrometry in the selective ion monitoring mode. The within-assay imprecision varied from 0.8-15.2% (mean 8.7%) and the between-assay imprecision from 4.1-13.9% (mean 9.3%), depending on compound and concentration level. The mean recovery of authentic standards added to urine extracts before hydrolysis varied from 96.6 to 105.5%. Values obtained from 10 Finnish omnivorous men are presented. Individual values for matairesinol (excretion range 3.3-59.9 nmol/24 h) and genistein (range 21.8-1180 nmol/24 h) in human urine have never been published before.