Individual Isoflavones Research Articles

Synergic Effect of Genistein and Daidzein on UVB‐Induced DNA Damage: An Effective Photoprotective Combination

The anti-inflammatory effects and antioxidant activities of individual isoflavones are well established although little is known about the photoprotective effect of their combination. The aim of this study was to investigate the photoprotective effects of different concentrations of genistein and daidzein individually or combined. We measured the expression levels of the cyclo-oxygenase-2 (COX-2) and growth arrest and DNA-damage inducible (Gadd45) genes, which are involved in inflammation and DNA repair, respectively, in BJ-5ta human skin fibroblasts irradiated with 60 mJ/cm2 UVB. We also determined the cellular response to UVB-induced DNA damage by Comet assay. We report that genistein and daidzein when administered combined, and at a specific concentration and ratio, exerted a synergistic photoprotective effect that was greater than the effect obtained with each isoflavone alone. The results reported herein suggest that low concentrations of genistein and daidzein combined may be good candidate ingredients for protective agents against UV-induced photodamage.

Higher bioavailability of isoflavones after a single ingestion of aglycone‐rich fermented soybeans compared with glucoside‐rich non‐fermented soybeans in Japanese postmenopausal women

There have been conflicting study results concerning how the food matrix affects the bioavailability of isoflavone aglycone and glucoside. In this study the bioavailability of isoflavones after a single ingestion of aglycone-rich fermented soybeans (Fsoy) and glucoside-rich non-fermented soybeans (Soy) was compared. Eleven healthy postmenopausal Japanese women were recruited for a randomised, double-blind, crossover trial and consumed Fsoy or Soy powder dissolved in hot water. Blood samples were collected 0, 1, 2, 3, 4, 6, 8, 12 and 24 h and urine samples from 0 to 48 h after ingestion of the powders. The Fsoy and Soy powders ingested had the same total isoflavone content (95 µmol), but the former was rich in aglycone (90.6 µmol) while the latter was rich in glucoside (81.9 µmol). Serum concentrations of total isoflavones after 1-4 h were significantly higher in the Fsoy group than in the Soy group. The Fsoy group showed significantly higher maximum concentration (Cmax: 2.79 ± 0.13 vs 1.74 ± 0.13 µmol L(-1) ) and area under the curve (AUC(0-24 h) : 23.78 ± 2.41 vs 19.95 ± 2.03 µmol day L(-1) ) and lower maximum concentration time (Tmax: 1.00 ± 0.00 vs 5.00 ± 0.67 h) compared with the Soy group. The cumulative urinary excretion of total isoflavones after 2 h was significantly higher in the Fsoy group than in the Soy group. Individual isoflavones (daidzein, genistein and glycitein) showed similar trends to total isoflavones. Equol (a metabolite from daidzein) did not differ between the two groups. The results of this study demonstrated that the isoflavones of aglycone-rich Fsoy were absorbed faster and in greater amounts than those of glucoside-rich Soy in postmenopausal Japanese women.

Method development and optimization for isoflavone quantification in dry soy extract containing products

Isoflavones are secondary metabolites belonging to flavonoids found in a variety of plants, especially soy (Glycine max L.). Due to the estrogen-like activity of these compounds several soy products are on the market and applied to relieve menopausal symptoms. The aim of our study was to develop a simple method for the determination of isoflavones in soy extract containing products. The main isoflavones of soybean are genistin, glycitin, daidzin and their respective acetyl, malonyl and aglycone forms. Quantitative measurement of each individual isoflavone is difficult because some of the reference compounds are not widely commercially available [1]. Keeping in mind that the biological effects of soy isoflavones depend upon aglycone form, hydrolysis of glycosides is a practical method for the quantitative determination of total isoflavones and assessment of biological value of extracts [2]. The objective of our investigation was to establish an acid hydrolysis method for the quantitative HPLC determination of total isoflavones including daidzein, genistein and glycitein. To optimize the extraction and hydrolysis of isoflavones, the effect of HCl concentration (1.5–6 N), hydrolysis time (25–210min) and temperature (30–100°C) on total isoflavone aglycone content was studied using an RP-HPLC-DAD method. By mathematical fitting and optimization methods optimum hydrolysis conditions for maximizing the quantification of isoflavones were determined (t=94min, cHCl=5.09 N, T=80°C). The experimentally verified model has a good coefficient of R2 (0,9928) and the recovery of isoflavones was 97.81–102.76%. The developed method allows a reliable and maximum determination of isoflavones in dry soy extract containing products.

Mixture effects of dietary flavonoids on steroid hormone synthesis in the human adrenocortical H295R cell line

Humans are exposed to a mixture of dietary flavonoids with a variety of potential beneficial and harmful effects. Flavonoids are endocrine disruptors, acting both at receptor level and by interfering with steroid hormone synthesis. Due to a high dietary intake and the potential to cause mixture effects, assessment of combined exposure of flavonoids is required. We have studied effects on cortisol, aldosterone, testosterone and oestradiol secretion of the individual isoflavones daidzein and genistein, the flavone apigenin and the mixture of the three flavonoids in human adrenocortical H295R cells. The most vulnerable targets of the flavonoids were the secretion of cortisol and testosterone, which were inhibited by daidzein and genistein with IC50 values below 1 μM. An equimolar mixture of the flavonoids caused inhibition of cortisol, aldosterone and testosterone secretion in an additive manner. The observed mixture effect was described well by both concentration addition (CA) and independent action (IA) prediction models. Both prediction models underestimated the effect on oestradiol secretion. We conclude that the three flavonoids exhibit specific effects on steroid hormone secretion. A mixture of the flavonoids caused additive effects emphasizing the need to assess flavonoids together as a group. The prediction models are valuable tools for mixture assessment.

Effect of Growth Stage and Pod Position on Soybean Seed Isoflavone Concentration

Field experiments were established during 2004 at two sites of the Emile A. Lods Agronomy Research Centre in Sainte-Anne-de-Bellevue, QC, Canada. Soil types were a fine sandy loam at one site (site A), and a Macdonald clay loam at the other (site B). During seed development and maturation, three replicates of 200 pods were collected from different parts of plants (from the top and base of plants) at three development stages; full-seed pod (R6), yellow pod (R7), and brown pod (R8), resulting in 6 treatments. Total and individual isoflavone concentrations were determined by high-performance liquid chromatography. Our results indicate that the individual and total isoflavone contents were influenced significantly by growth stage and pod position. The maximum individual and total isoflavone contents were recorded when the soybean seeds were collected from the base parts of plants at brown pod stage (R8). The maximum protein content of 468 g kg-1 was obtained by collecting soybean seeds at the earlier growth stage (R6). Also, the soybean seeds developing at the top parts of plants accumulate greater amount of protein than those from base region. On the other hand, soybean seeds developing at the base parts of plants (first 20 cm from soil surface) accumulate greater amount of oil than those from the top (last 20 cm from soil surface).

Abstract 2815: Soy increases risk of rectal cancer among Singapore Chinese women

Abstract Background. Estrogens are thought to play a protective role in colorectal carcinogenesis, however, recent findings for positive associations with circulating estrogens and colorectal cancer risk among postmenopausal women suggest otherwise. Soy isoflavones are phytoestrogens that can display either estrogenic or antiestrogenic properties depending on estrogen receptor signaling, as well as the estrogen milieu. Inconsistent findings for soy and colorectal cancer risk from observational studies may be due to the relatively low and mainly adulthood intake, as well as differences in the estrogen milieu levels in the most studied populations. Methods. We examined the relationship between soy isoflavone intake and colorectal cancer in a population-based cohort of 61,314 Singapore Chinese men and women that was established between 1993 and 1998. As of December 31, 2007, 1,167 (640 male and 527 female) incident colorectal cancer cases had been diagnosed. Diet was assessed at baseline with a validated 165-item quantitative food frequency questionnaire. We used Cox regression methods to calculate hazard ratios (HR) and 95% confidence intervals (CI) adjusted for age at baseline, interview year, dialect group, education level, smoking, alcohol use, body mass index (BMI), physical activity, family history of colorectal cancer and total energy intake. Results. No association was observed between total soy isoflavone intake and risk of colorectal, colon or rectal cancer, overall or among men. Among women, we observed a 43% increase in rectal cancer risk (HR=1.43; 95% CI: 0.92, 2.21; P for trend = 0.11), comparing 4th to 1st quartile of intake (P for interaction by sex=0.04). The association with soy isoflavones was stronger among women who were postmenopausal at baseline (HR=1.64; 95% CI: 1.03, 2.60; P for trend = 0.01). The associations for rectal cancer among postmenopausal women were similar with individual soy isoflavones, soyfoods and soy protein intake. The estrogen milieu was low among postmenopausal women in our cohort. For example, only 6% reported ever use of exogenous hormones and the median BMI was 23.2 kg/m2. Conclusion. We report a detrimental effect for dietary soy isoflavones on rectal cancer risk among postmenopausal women. Our finding suggests that in a low estrogen milieu phytoestrogens have procarcinogenic effects in the rectum that require lifelong exposure to relatively high levels of intake. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2815.

Abstract 5725: Differential effects of dietary soy isoflavones on cancer metastasis

Abstract The role of soy foods in cancer prevention is known but their effects on cancer metastasis remain to be understood. The purpose of this study is to investigate the effects and mechanism of action of dietary soy isoflavones in established carcinomas. This objective was achieved by testing the effect of the individual and combined soy isoflavones on progression of mammary fat pad tumors in nude mice created from green fluorescent protein (GFP) tagged-MDA-MB-435 metastatic cancer cells. Following tumor establishment, mice were orally gavaged with vehicle or soy isoflavones: genistein (10 mg/kg body weight (BW)), daidzein (10 mg/kg BW), or genistein (50%), daidzein (40%), and glycitein (10%) three times per week. Tumor progression was quantified by whole body fluorescence image analysis twice a week followed by microscopic image analysis of excised organs for metastases. Results show that daidzein significantly increased while genistein decreased mammary tumor growth by 38% and 33% respectively. Daidzein increased lung, heart, and kidney metastases while genistein decreased bone and liver metastases. Combined soy isoflavones did not affect primary mammary tumor growth but increased metastasis to all organs tested; i.e. lung, liver, heart, kidney, and bones. Phosphoinositide-3-kinase (PI3-K) pathway real time PCR array analysis on excised tumors demonstrates that genistein significantly downregulated 26% of the genes tested, including Rho GTPases RHOA, RAC1, and CDC42, and their downstream effector PAK1 that are known regulators of cancer cell invasion, and thus, metastasis. Daidzein upregulated 14% of the genes including CCND1, GRB2, MAPK1, JUN, CTNNB1, IRS1, EIF4G1, and GSK3B that regulate proliferation and protein synthesis. Combined soy treatment significantly increased EIF4E and decreased TIRAP expression. Western blotting of mammary tumor extracts following genistein, daidzein, or combined soy isoflavones show that genistein downregulates RhoA, Rac1, and Cdc42 while daidzein upregulates Rac1, GSK3, and eIF4G1 protein expression. Combined soy isoflavones did not show significant differences in expression of Rho GTPases or PAK. In conclusion, downregulation of Rho GTPases by genistein may reduce mammary tumor growth and metastasis while upregulation of eIF4G and Rac1 by daidzein may increase mammary tumor growth and metastasis. Consumption of soy foods that contain both genistein and daidzein may neutralize their differential effects on primary tumor growth. The increased metastasis but not primary tumor growth in response to combined soy isoflavones indicates that even though dietary soy has been implicated in cancer prevention, caution must be exercised in dietary decisions of soy foods for cancer patients and survivors. This research was supported by AICR IIG 03-31-06 and NIH/NIGMS SC3GM084824 to SD and NCCR/NIH 2G12RR003035 and S06GM050695 to UCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5725.

Overnight urinary excretion of isoflavones as an indicator for dietary isoflavone intake in Korean girls of pubertal age

Little is known about the bioavailability of isoflavones in children. Previous studies have shown that children excrete more isoflavone in urine compared with adults. Thus we examined the relationship between usual dietary isoflavone intake and the urinary excretion of isoflavonoids in Korean girls of pubertal age. Twelve girls each were selected from the lowest and the highest quartiles of isoflavone intake among 252 Korean girls aged 8-11 years. Age, BMI and sexual maturation stage were matched between the two groups. Dietary intakes for 3 d by diet record and overnight urine samples were collected at baseline and at 6 and 12 months. Total and individual isoflavone (daidzein, genistein and glycitein) intakes were calculated from diet records. The parent isoflavone compounds (daidzein, genistein and glycitein) and their metabolites (equol, O-desmethylangolensin (O-DMA), dihydrodaidzein and dihydrogenistein) present in the urine samples were analysed using liquid chromatography-MS. Intake levels of total and individual isoflavone compounds were significantly higher in the high isoflavone (HI) group than the levels in the low isoflavone (LI) group (P < 0.05). Urinary excretion of all isoflavone parent compounds was significantly higher in the HI group than in the LI group (P < 0.0001). Among isoflavone metabolites, only O-DMA and total metabolites were significantly different (P < 0.05). Total isoflavone intake was highly correlated with the urinary excretion of total parent compounds (r 0.68; P < 0.01), parent compounds plus their metabolites (r 0.66-0.69; P < 0.01) and total isoflavonoids (r 0.72; P < 0.0001). In conclusion, overnight urinary excretion of total isoflavonoids is a reliable biomarker of usual isoflavone intake in Korean girls of pubertal age.

Comparative Studies on the Chemical and Cell-Based Antioxidant Activities and Antitumor Cell Proliferation Properties of Soy Milk Manufactured by Conventional and Commercial UHT Methods

The aims of this work were to compare antiproliferation, antioxidant activities and total phytochemicals and individual isoflavone profiles in soy milk processed by various methods including traditional stove cooking, direct steam injection, direct ultrahigh temperature (UHT), indirect UHT, and a two-stage simulated industry method, and a selected commercial soy milk product. Various processing methods significantly affected total saponin, phytic acid, and total phenolic content and individual isoflavone distribution. The laboratory UHT and the two-stage processed soy milk exhibited relatively higher total phenolic content, total flavonoid content, saponin and phytic acid than those processed by the traditional and steam processed methods. Thermal processing caused obvious intertransformation but did not cause severe degradation except for breaking down of aglycons. Thermal processing significantly increased antioxidant capacities of soy milk determined by chemical analyses, but decreased cellular antioxidant capacities as compared to the raw soy milk. The raw and all processed soy milk exhibited antipoliferative activities against human HL-60 leukemia cells, AGS gastric tumor cells, and DU145 prostate cancer cells in a dose-dependent manner. The raw soy milk, but not the processed soy milk, exhibited a dose-dependent antiproliferative effect against colorectal adenocarcinoma Caco-2 cells. Taken together, these results indicate that various thermal processing methods change not only phytochemcials but also potential health-promoting effects of soy milk.

Differential effects of whole soy extract and soy isoflavones on apoptosis in prostate cancer cells

Previous studies have suggested that soy isoflavones exert anticarcinogenic effects against prostate cancer. We propose that soy extracts, containing a mixture of soy isoflavones and other bioactive components, would be a more potent chemo-preventive agent than individual soy isoflavones. We compared the apoptotic effects of whole soy extracts and individual soy isoflavones, genistein and daidzein, on prostate cancer cells. The soy extract contained 50% w/w of total isoflavones with approximately 1:5.5:3.5 ratios of genistin, daidzin and glycitin, respectively. Benign prostate hyperplasia (BPH-1), LnCap and PC3 cells were treated with varying concentrations of soy extract, genistein or daidzein and analyzed for cell cycle alterations and induction of apoptosis. At equal concentrations (25 micromol/L), soy extract induced a significantly higher percentage of cells undergoing apoptosis than genistein or daidzein (P < 0.001). No significant changes in cell cycle arrest or apoptosis were observed in non-cancerous BPH-1 cells treated with soy extract, suggesting that the effects of soy extract may be tumor cell specific. On the contrary, both genistein and daidzein induced apoptosis in BPH-1 cells, suggesting that individual isoflavones may have cytotoxicity in non-cancerous cells. Soy extracts also increased Bax expression in PC3 cells, but no significant changes in nuclear factor kappaB (NF kappaB) activation were detected, suggesting that the induction of apoptosis was independent of the NF kappaB pathway. Food products that bear a combination of active compounds may be more efficacious and safer as chemo-preventive agents than individual compounds. This 'whole-food'-based approach is significant for the development of public health recommendations for prostate cancer prevention.

The Effect of Soybean-Derived Phytoestrogens on Concentrations of Plasma Isoflavones, 15-keto-13,14-dihydroprostaglandin F2α and Progesterone in Dairy Cows

The objective of the study was to determine the effect of soybean-derived phytoestrogens and their metabolites on the activity of sex hormones during the oestrous cycle in multiparous lactating dairy cows. The experiment was carried out on 4 multiparous lactating Holstein cows in the form of replicated Latin square in double reversal design. The experiment in the total length of 168 days was divided into 4 periods of 42 days, each consisting of a 21-day preliminary period and a 21-day collecting period. Cows were divided into 2 groups of 2 cows. The control group (C) was fed a diet based on extruded rapeseed cake while the experimental group (S) was fed a diet containing extruded full-fat soya. The intake of total isoflavones was 3297 mg/d in S and 58.0 mg/d in C (P &lt; 0.001). The concentrations of individual isoflavones, it is daidzein, genistein and equol in plasma were significantly higher in the experimental group S (49.3, 78.7 and 218.8 ng/ml, respectively) than in the control group C (13.5, 42.9 and 18.3 ng/ml, respectively, P &lt; 0.001). Plasma concentration of progesterone throughout the oestrous cycle was not influenced by the diet used (P &gt; 0.05). Plasma concentration of prostaglandine PGFM throughout the oestrous cycle in the experimental group (S) tended to be higher (P = 0.095) than in the control group (C). No differences in the length of the oestrous cycle between the cows fed different diets were observed.

PENGARUH PENGOLAHAN KEDELAI MENJADI TEMPE DAN PEMASAKAN TEMPE TERHADAP KADAR ISOFLAVON (EFFECTS OF SOYBEAN PROCESSING BECOMING TEMPEH AND THE COOKING OF TEMPEH ON ISOFLAVONES LEVEL)

ABSTRACT Background : Research over the past two decades has provided significant clinical trial and epidemiological evidence for health benefits of the consumption of soybean-based foods. A health claim indicating that high soybean consumption is associated with a lower risk of coronary heart disease (CHD). Compositions of nutrient and non-nutrient in soybean have been examination and give the contribution on lower risk of CHD especially on improve of lipid profile. Isoflavones is a non-nutrient that abundant in soybean. Tempeh is fermented soybean that popular as Indonesian traditional food and content of isoflavones is greater than soybean. Objective : to study effect of soybean processing becoming tempeh and the cooking of tempeh on isoflavones level. Methods : The samples of this study is raw tempeh and steamed tempeh. The analysis of isoflavones has used high performance liquid chromatography (HPLC). Results : During soybean processing becoming tempeh, twice boiling of soybean produce result isoflavones 47.4 percent greater than once boiling. Steaming tempeh result minimized isoflavones reduction (13.3%). Although there is no dietary recommendation for individual isoflavones, may be great benefit in increased consumption of tempeh. [Penel Gizi Makan 2010, 33(2): 148-153] Keywords : tempeh, processing, isoflavones

Changes in anthocyanin and isoflavone concentrations in black seed-coated soybean at different planting locations

This study assessed the altitudinal variations in the anthocyanin and isoflavone contents of six black seed coated soybean [Glycine max (L.) Merrill] cultivars. The black soybean cultivars Heugcheong, Seonheuk, Geomjeong 1, Geomjeong 2, Cheongja 2, and Cheongja 3 were planted at Milyang (12 m above mean sea level — low altitude) and Muju (600 m — high altitude), Korea on 10 June 2005 and 2006. The total anthocyanin and isoflavone contents and individual components were investigated by reverse-phase high performance liquid chromatography (HPLC). All black soybean cultivars cultivated in high altitude possessed significantly higher total anthocyanin (p < 0.01) and isoflavone (p < 0.01) contents than those grown in low altitude. For anthocyanin composition, cyanidin-3-O-glucoside, cyanidin-3-O-galactoside, and peonidin-3-O-glucoside contents were significantly higher while delphinidin-3-O-glucoside contents was significantly lower at high altitude. The composition of individual isoflavones, 6″-O-malonyldaidzin, and 6″-O-malonylgenistin contents significantly increased at high altitude.

Isoflavones, Flavan-3-ols, Phenolic Acids, Total Phenolic Profiles, and Antioxidant Capacities of Soy Milk As Affected by Ultrahigh-Temperature and Traditional Processing Methods

The objectives of this work were to assess antioxidant activities and phenolic compounds of soy milk as affected by traditional and ultrahigh-temperature (UHT) processing. Three soybean varieties were processed into raw soy milk and then cooked soy milk by indirect and direct UHT methods (both at 143 degrees C for 60 s) and traditional cooking (stove cooking and steam injection) methods (both at 100 degrees C for 20 min). Total phenolic content (TPC), total flavonoid content (TFC), phenolic acids, isoflavones, flavan-3-ols, and anthocyanins were quantified. DPPH free radical scavenging activity, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) were analyzed. As compared to the raw soy milk, all thermal processing significantly (p < 0.05) reduced TPC values and significantly (p < 0.05) increased TFC values for all soybean varieties. All processing methods significantly (p < 0.05) increased DPPH and FRAP values in the soy milk processed from yellow soybean varieties Proto and IA 2032. UHT processing increased their ORAC values, but traditional and steam processing reduced their ORAC values. However, in the case of the soy milk from black soybean, all processing reduced ORAC values as compared to the raw soy milk. None of processing affected total phenolic acids, chlorogenic, and trans-cinnamic acid, as well as (+)-catechin. However, all processing significantly (p < 0.05) affected contents of total isoflavones and individual isoflavones. Thermal processing caused significant (p < 0.05) increases in 7-O-beta-glucosides and acetylglucosides, but caused significant (p < 0.05) decreases in malonylglucosides and aglycones. Indirect UHT processing transformed more isoflavones from malonylglucosides into 7-O-beta-glucosides than the direct UHT did.

Ecologic Difference of Isoflavones Content in Soybean Seeds in Heilongjiang Province

Isoflavones in soybean is paid widely and extensively attention due to its function in physical health care. As important secondary metabolic compounds in soybean seeds, isoflavones content have been reported to be easily impacted by environment. To survey the difference of isoflavones content in soybean seeds in different environment in Heilongjiang, which is main area to plant soybean in China, four cultivars were planted at five locations from 2005 to 2007. There were significant difference in total and individual isoflavones contents among years, locations, genotypes and genotypes × locations. The mean contents of total isoflavones and individual hydrolyzing isoflavones were significantly higher in 2006 than those in the other two years. And, total and individual isoflavone contents were significantly positively correlated with latitude of the locations at the 0.01 probability level. As a whole, there are predominant production regions for isoflavones of soybean seeds in Heilongjiang province, so it was feasible to categorize the production regions based on soybean isoflavone in Heilongjiang province.

Phytoestrogen consumption and endometrial cancer risk: a population-based case–control study in New Jersey

Phytoestrogens have been shown to exert anti-estrogenic and estrogenic effects in some tissues, including the breast. However, only a few studies have evaluated their role in endometrial cancer risk. We evaluated this association in a population-based case-control study in New Jersey. A total of 424 cases and 398 controls completed an interview, including a food frequency questionnaire with supplemental questions for phytoestrogen foods. Risk estimates were derived using an unconditional logistic regression, adjusting for major risk factors for endometrial cancer. There was some suggestion of a decreased risk with quercetin intake (OR: 0.65; 95% CI: 0.41-1.01 for the highest compared to the lowest quartile; p for trend: 0.02). We found a limited evidence of an association with any of the lignans evaluated, total lignans, coumestrol, individual isoflavones, total isoflavones, or total phytoestrogens. However, there was some suggestion of an inverse association with total isoflavone intake limited to lean women (BMI <25; OR for the highest tertile: 0.50; 95% CI: 0.25-0.98) and those with a waist-to-hip ratio <or=0.85 (OR: 0.59; 95% CI: 0.33-1.05). There was no evidence of effect modification by HRT use. This study suggests a reduction in endometrial cancer risk with quercetin intake and with isoflavone intake in lean women.

Estrogen/isoflavone interactions in cynomolgus macaques (Macaca fascicularis)

Soy isoflavones are phytoestrogenic components of dietary soy, which are widely consumed for their potential health benefits. Soy isoflavones appear to decrease breast and endometrial cancer risk in human observational studies, but paradoxically stimulate growth of breast cancer cells in culture and uterine enlargement in rodents. We have shown that these compounds are not estrogenic in cynomolgus monkeys even at relatively high doses, but that they reduce estrogen-induced proliferative responses of the breast and endometrium. This effect may be mediated through estrogen receptor interactions and/or modulation of endogenous estrogen metabolism. Interindividual variation in isoflavone absorption and metabolism contributes to the degree of estrogen antagonistic effect. Our recent studies have also shown that individual isoflavone metabolites such as glyceollins may have unique selective estrogen receptor modulator-like activity, acting as tissue-specific antagonists without agonist activity. Rodent studies and human epidemiologic data suggest that timing of exposure and dose relative to endogenous estrogen concentrations are important determinants of effect, and studies of dietary soy on breast development and pubertal maturation are under way. Because soy isoflavones are both abundant in standard monkey chow diets and widely available as dietary supplements for human beings, these findings have broad relevance to the health of human and nonhuman primates.

Determination of isoflavones in nutritional supplements by HPLC with coulometric electrode array detection

In the present study eleven soy and/or red clover based supplements were analyzed after acid hydrolysis or direct extraction with 70% aqueous ethanol for their content of total isoflavone aglucones and free aglucones plus glucosides by high performance liquid chromatography in gradient elution mode coupled with coulometric electrode array detection. The ratio of the individual isoflavones and the conjugation pattern turned out to be highly variable in the investigated products. Whereas red clover based supplements contained isoflavones (mainly formononetin and biochanin A) exclusively in free form, soy containing preparations showed variable proportions of conjugated isoflavones. The total isoflavone aglucone content in products intended for direct consumption ranged from 12.0 to 45.6 mg per capsule or tablet, whereas the content of free aglucones and glucosides was between 12.2 and 51.6 mg per capsule or tablet. The experimentally determined isoflavone aglucone content was in agreement with or higher than the manufacturer’s claim in 6 of the 11 investigated products. Expression of the isoflavone content as a sum of free aglucones and glucosides raised the number of matched claims to 8.

Comparison of the estrogenic potencies of standardized soy extracts by immature rat uterotrophic bioassay

Soy phytoestrogens, isoflavones, are a primary class of plant-based estrogen alternatives being sold over the counter nowadays. Genistein, daidzein and glycitein are the major isoflavones found in soybeans, as aglycones and glycosides. Each isoflavone shows distinctive estrogenic activity and pharmacokinetics. Soy dry extracts, employed as pharmaceutical raw material for manufacturing isoflavone supplements, are standardized to contain 40% of total isoflavones, but the amount of each isoflavone is highly diverse. The influence of these compositional differences on the estrogenic potency of soy extracts was evaluated by uterotrophic bioassay. Five commercial samples of standardized soy dry extract, homogeneously suspended in arachis oil, were administered per os in serial doses (125-4150 mg/kg bw/day) to immature female rats for 3 days. Soy extract samples with considerable diversity in isoflavone composition revealed different estrogenic potencies. Our results indicate a need of standardization of the individual isoflavone content in soy extracts.

Ultrasound-assisted extraction of isoflavones from soy beverages blended with fruit juices

A new method for the fast determination of isoflavones from soy beverages blended with fruit juices without the need of freeze-drying the sample was developed. During the method development, several parameters were studied: solvent (methanol and ethanol), sample:solvent ratio (5:1 to 0.2:1), temperature (10–60 °C) and extraction time (5–30 min). The most important parameter for the extraction of isoflavones from soy drinks was the sample:solvent ratio. The optimized method consists of extracting the sample with ethanol with a sample:solvent ratio of 0.2:1 on an ultrasound bath at 45 °C during 20 min. Also, samples were freeze-dried, extracted using conventional method and compared with the optimized method and no significant difference was observed on total and individual isoflavone concentration. The most representative samples from the Spanish market, with a wide variation of isoflavone concentration were analyzed using the optimized method. Differences between manufacturers reached an almost 10 times fold variation. Overall isoflavone concentration ranged from 6.7 to 58.2 mg L −1.