Soybean Foods and Their Benefits: Potential Mechanisms of Action

Scalable purification and characterization of the anticancer lunasin peptide from soybean

Lunasin is a peptide derived from the soybean 2S albumin seed protein that has both anticancer and anti-inflammatory activities. Large-scale animal studies and human clinical trials to determine the efficacy of lunasin in vivo have been hampered by the cost of synthetic lunasin and the lack of a method for obtaining gram quantities of highly purified lunasin from plant sources. The goal of this study was to develop a large-scale method to generate highly purified lunasin from defatted soy flour. A scalable method was developed that utilizes the sequential application of anion-exchange chromatography, ultrafiltration, and reversed-phase chromatography. This method generates lunasin preparations of >99% purity with a yield of 442 mg/kg defatted soy flour. Mass spectrometry of the purified lunasin revealed that the peptide is 44 amino acids in length and represents the original published sequence of lunasin with an additional C-terminal asparagine residue. Histone-binding assays demonstrated that the biological activity of the purified lunasin was similar to that of synthetic lunasin. This study provides a robust method for purifying commercial-scale quantities of biologically-active lunasin and clearly identifies the predominant form of lunasin in soy flour. This method will greatly facilitate the development of lunasin as a potential nutraceutical or therapeutic anticancer agent.

Hydrolysis of isoflavone glycosides by a thermostable β-glucosidase from Pyrococcus furiosus

The recombinant β-glucosidase from the hyperthermophilic archaeon Pyrococcus furiosus was purified with a specific activity of 330 U/mg for genistin by His-trap chromatography. The specific activity of the purified enzyme followed the order genistin > daidzin > glycitin> malonyl glycitin > malonyl daidzin > malonyl genistin. The hydrolytic activity for genistin was highest at pH 6.0 and 95 °C with a half-life of 59 h, a K(m) of 0.5 mM, and a k(cat) of 6050 1/s. The enzyme completely hydrolyzed 1.0 mM genistin, daidzin, and glycitin within 100, 140, and 180 min, respectively. The soybean flour extract at 7.5% (w/v) contained 1.0 mM genistin, 0.9 mM daidzin, and 0.3 mM glycitin. Genistin, daidzin, and glycitin in the soybean flour extract were completely hydrolyzed after 60, 75, and 120 min, respectively. Of the reported β-glucosidases, P. furiosusβ-glucosidase exhibited the highest thermostability, k(cat), k(cat)/K(m), yield, and productivity for hydrolyzing genistin. These results suggest that this enzyme may be useful for the industrial hydrolysis of isoflavone glycosides.

Oral toxicological studies of black soybean (Glycine max) hull extract: acute studies in rats and mice, and chronic studies in mice

Black soybean (Glycine max) has been used for traditional medicine and food in Asian countries, but safety of its hull has not been studied. We conducted acute and chronic oral toxicity studies. For the acute study, an extract of black soybean hull (BE; 2.5 g/kg body weight) was administered singly by intragastric intubation to Sprague-Dawley rats and C57BL/6 mice. There was no death or significant decrease in body weight in rats and mice, and the oral LD(50) of BE was >2.5 g/kg body weight. In the chronic study, BE was administered at dietary levels of 0% (control), 2.0%, and 5.0% to male and female C57BL/6 mice for 26 weeks. No mortality or toxicologically significant clinical changes were observed through the experimental period. Although body weights, as well as abdominal fat, blood levels of triglyceride and total cholesterol in 5.0% males were significantly lower than that in control and 2.0% groups, these changes were considered not to be adverse. Hematology and histopathological observation revealed no toxicologically significant changes. The no-observed adverse-effect-level of BE was estimated to be 5.0% in the diet (5074.1 mg/kg body weight/day for males and 7617.9 mg/kg body weight/day for females).

Effect of soybean supplementation on the memory of alprazolam-induced amnesic mice

Soybean, Glycine max (L.) Merr. (Leguminoseae), is known as golden bean. It contains vegetable protein, oligosaccharide, dietary fiber, vitamins, isoflavones and minerals. Earlier studies have demonstrated a cholesterol lowering, skin protective, antitumour, antidiabetic and antioxidative potential of soybean. Soy isoflavones are also utilized as estrogen replacement therapy in postmenopausal women. The present study was undertaken to investigate the effect of soybean on memory of mice when consumed along with diet. Soybean was administered chronically for 60 consecutive days as three soybean diets viz. Soy2, Soy5, Soy10. These diet contains soybean in normal diet at concentration of 2%, 5%, 10% w/w respectively. Passive avoidance paradigm and elevated plus maze served as exteroceptive behavioral models for testing memory. Alprazolam (0.5 mg/kg; i.p.) induced amnesia served as interoceptive behavioral model. The administration of soybean significantly reversed alprazolam-induced amnesia in a dose-dependent manner as indicated by the increased step down latency of mice using passive avoidance paradigm and increased transfer latency using elevated plus maze. Theses results suggest that consumption of soybean in diet may not only improve memory but also reverse the memory deficits, owing to its multifarious activities. It would be worthwhile to explore the potential of this nutrient in the management of Alzheimer's disease.

Characterization of a GH3 family β-glucosidase from Dictyoglomus turgidum and its application to the hydrolysis of isoflavone glycosides in spent coffee grounds

A recombinant β-glucosidase from Dictyoglomus turgidum was purified with a specific activity of 31 U/mg by His-Trap affinity chromatography. D. turgidum β-glucosidase was identified as a memmber of the glycoside hydrolase (GH) 3 family on the basis of its amino acid sequence. The native enzyme existed as an 86 kDa monomer with an activity maximum at pH 5 and 85 °C with a half-life of 334 min. The hydrolytic activity of the enzyme with aryl-glycoside substrates was the highest for p-nitrophenyl (pNP)-β-D-glucopyranoside (with a K(m) of 1.3 mM and a k(cat) of 13900 1/s), followed by oNP-β-D-glucopyranoside, pNP-β-D-xylopyranoside, pNP-β-D-fucopyranoside, and pNP-β-D-galactopyranoside. However, no activity was observed for oNP-β-D-galactopyranoside, pNP-α-D-glucopyranoside, pNP-α-D-glucopyranoside, pNP-β-D-mannopyranoside, pNP-β-L-arabinopyranoside, and pNP-α-L-rhamnopyranoside. The hydrolytic activity of the β-glucosidase for coffee isoflavones followed the order genistin (with a K(m) of 0.67 mM and a k(cat) of 5750 1/s) > daidzin > ononin > glycitin. The concentrations of daidzin in ground coffee and spent coffee grounds were 160 and 107 μg/g, respectively, but other isoflavones were present at low concentrations or absent. The enzyme completely hydrolyzed 1.2 mM daidzin in spent coffee grounds after 2 h, with a productivity of 0.6 mM/h. This is the first report concerning the enzymatic hydrolysis of isoflavone glycosides in spent coffee grounds.

Black soybean extract can attenuate thrombosis through inhibition of collagen-induced platelet activation

Many clinical trials have demonstrated the beneficial effects of soybean (Glycine max) on general cardiovascular health. Among a variety of soybeans, black soybean is known to display diverse biological activities superior to those of yellow and green soybeans, such as in antioxidant, anti-inflammatory and anticancer activities. However, few studies have been directed on the effect of black soybean on cardiovascular function. In this study, we aimed to investigate the effect of black soybean extract (BB) on platelet activation, a key contributor to thrombotic diseases. In freshly isolated human platelets, BB has shown potent inhibitory activity on collagen-induced platelet aggregation, while yellow soybean extract had marginal activity only. BB also attenuated serotonin secretion and P-selectin expression, which are important factors for the platelet-tissue interaction along with thromboxane A(2) formation. These in vitro results were further confirmed in an ex vivo platelet aggregation measurement and in vivo venous thrombosis model where oral administration of BB reduced collagen-induced platelet aggregation and FeCl(3)-induced thrombus formation significantly. A potential active ingredient for antiplatelet effects of BB was isolated and identified to be adenosine through bioassay-directed fractionation and NMR and ESI-MS analyses. These results indicate that black soybean can be a novel dietary supplement for the prevention of cardiovascular risks and the improvement of blood circulation.

Alcohol-fermented soybean increases the expression of receptor-interacting protein 2 and IκB kinase β in mouse peritoneal macrophages

Soybean is a useful component of traditional Korean medicine with well-documented health-promoting effects. We investigated the effects of alcohol-fermented soybean (AFS) on immune function. When AFS treatment was used in combination with recombinant interferon-γ (rIFN-γ), there was a marked cooperative induction of nitric oxide (NO) and tumor necrosis factor (TNF)-α production in mouse peritoneal macrophages. AFS increased the expression of inducible NO synthase mRNA and protein in rIFN-γ-primed macrophages. Treating macrophages with pyrrolidine dithiocarbamate, an inhibitor of nuclear factor-κB (NF-κB), decreased the synergistic effects of AFS. In addition, AFS in combination with rIFN-γ increased the phosphorylation of p38 and c-Jun N-terminal kinase (JNK) but not extracellular signal-regulated kinase. However, AFS had no effect on phosphorylation of mitogen-activated protein kinases by itself. The p38 inhibitor SB203580 or the JNK inhibitor SP600125 inhibited the AFS-induced NO and TNF-α production. When AFS was used in combination with rIFN-γ, there was a co-operative activation of NF-κB and receptor-interacting protein 2 (Rip2)/IκB kinase (IKK)-β. Our results indicate that AFS increases the production of NO and TNF-α through the activation of Rip2/IKK-β in rIFN-γ-primed macrophages.

Isoflavone soy protein supplementation and atherosclerosis progression in healthy postmenopausal women: a randomized controlled trial

BACKGROUND AND PURPOSE

Although epidemiological and experimental studies suggest that dietary intake of soy may be cardioprotective, use of isoflavone soy protein (ISP) supplementation as a primary preventive therapy remains unexplored. We determined whether ISP reduces subclinical atherosclerosis assessed as carotid artery intima-media thickness progression.

METHODS

In a double-blind, placebo-controlled trial, 350 postmenopausal women 45 to 92 years of age without diabetes and cardiovascular disease were randomized to 2 evenly divided daily doses of 25 g soy protein containing 91 mg aglycon isoflavone equivalents or placebo for 2.7 years.

RESULTS

Overall, mean (95% CI) carotid artery intima-media thickness progression rate was 4.77 (3.39-6.16) μm/year in the ISP group and 5.68 (4.30-7.06) μm/year in the placebo group. Although carotid artery intima-media thickness progression was reduced on average by 16% in the ISP group relative to the placebo group, this treatment effect was not statistically significant (P=0.36). Among the subgroup of women who were randomized within 5 years of menopause, ISP participants had on average a 68% lower carotid artery intima-media thickness progression rate than placebo participants 2.16 (-1.10 to 5.43) versus 6.79 (3.56-10.01) μm/year (P=0.05). ISP supplementation had a null effect on women who were >5 years beyond menopause when randomized. There were no major adverse events from ISP supplementation.

CONCLUSIONS

ISP supplementation did not significantly reduce subclinical atherosclerosis progression in postmenopausal women. Subgroup analysis suggests that ISP supplementation may reduce subclinical atherosclerosis in healthy young (median age, 53 years) women at low-risk for cardiovascular disease who were <5 years postmenopausal. These first trial results of their kind warrant further investigation.

Tofu (soybean curd) lowers serum lipid levels and modulates hepatic gene expression involved in lipogenesis primarily through its protein, not isoflavone, component in rats

Although soy foods are recommended to prevent hyperlipidemia and related diseases, it is unclear how their active ingredients exert their effects. Here, the effects of tofu (soybean curd) and its putative active components, protein and isoflavone, on lipid metabolism in male rats were compared. Tofu and soy protein significantly lowered serum triacylglycerol and cholesterol levels compared to casein and, through microarray analyses, were found to exclusively alter transcriptomes involved in fatty acid and/or steroid synthesis in the liver, where most of the serum lipids are synthesized. In contrast, isoflavone supplementation had little effect on serum lipid levels or gene expression and exerted no synergistic effects with soy protein or tofu. The importance of the proteinaceous components was further confirmed by the lower activity of enzymes involved in lipogenesis. From these findings it was concluded that the protein, not isoflavone, fraction of soy reduces lipogenesis in liver through gene expression and that this may result in lower serum lipid levels.

Legumes and soy products consumption and functional disability in older women

OBJECTIVES

This study was to examine the association between frequency of legumes and soy products consumption and functional disability in older Korean women.

STUDY DESIGN

Cross-sectional study. Data came from the 2005 Korea National Health and Nutrition Examination Survey (KNHANES). Subjects were 562 women aged 65 years and older living in the community.

MAIN OUTCOME MEASURES

Frequency of legume consumption was obtained by using food frequency questionnaire and functional disability was assessed using the instrumental activities of daily living (IADL) and ADL scales. Poisson regression analyses were conducted to examine the association of frequency of legume and soy consumption with functional disability, controlling for covariates.

RESULTS

Dietary intake of legumes and soy products was associated with a significantly reduced risk of IADL disability after controlling for potential risk factors (p = 0.002 for trend). Compared with women who consumed legumes and soy products < 1 time per week, those who consumed ≥ 3 times per day had a reduced risk of IADL disability (prevalence ratio = 0.70; 95% confidence interval: 0.51-0.96). In contrast, legumes and soy products consumption was not significantly associated with ADL disability.

CONCLUSIONS

Frequent legumes and soy products consumption was inversely associated with IADL disability in older women. Further studies are needed to clarify the protective effect of legume consumption on functional disability in older people.

Phenolic composition and antioxidant activity in seed coats of 60 Chinese black soybean (Glycine max L. Merr.) varieties

Phenolics in black soybean seed coat (BSSC) are considered to be responsible for the health benefits of black soybean. BSSCs of 60 Chinese varieties were examined for phenolic contents, anthocyanin profiles, and antioxidant activity. Total phenolic and condensed tannin contents ranged from 512.2 to 6057.9 mg gallic acid equivalents/100 g and from 137.2 to 1741.1 mg (+)-catechin equivalents/100 g, respectively. Six anthocyanins (delphinidin-3-glucoside, cyanidin-3-galactoside, cyanidin-3-glucoside, petunidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside) were detected by HPLC. Total anthocyanin contents (TAC) were from 98.8 to 2132.5 mg/100 g, and cyanidin-3-glucoside was the most abundant anthocyanin in all varieties, with a distribution of 48.8-94.1% of TAC. Antioxidant properties detected by DPPH, FRAP, and ORAC methods all showed wide variations ranging from 4.8 to 65.3 μg/100 mL (expressed as EC(50)), from 17.5 to 105.8 units/g, and from 42.5 to 1834.6 μmol Trolox equivalent/g, respectively. Sixty varieties were classified into four groups by hierarchical clustering analysis, and group 4 consisting of nine varieties had the highest phytochemicals content and antioxidant activity.

β-carboline derivatives and diphenols from soy sauce are in vitro quinone reductase (QR) inducers

A murine hepatoma (Hepa 1c1c7) cellular bioassay was used to guide the isolation of phase II enzyme inducers from fermented soy sauce, using quinone reductase (QR) as a biomarker. A crude ethyl acetate extract, accounting for 8.7% of nonsalt soluble solids of soy sauce, was found to double relative QR specific activity at 25 μg/mL (concentration required to double was defined as a "CD value"). Further silica gel column fractionation yielded 17 fractions, 16 of which exhibited CD values for QR induction of <100 μg/mL. The four most potent fractions were subfractionated by column and preparative thin layer chromatography, leading to the isolation and identification of two phenolic compounds (catechol and daidzein) and two β-carbolines (flazin and perlolyrin), with respective CD values of 8, 35, 42, and 2 μM. Western blots confirmed that the increases in QR activity corresponded to dose-dependent increases in cellular levels of NAD[P]H:quinone oxidoreductase 1 protein by these four QR inducers. To the authors' knowledge, this is the first report on the ability of β-carboline-derived alkaloids to induce phase II enzymes.

Chemopreventive potential of synergy1 and soybean in reducing azoxymethane-induced aberrant crypt foci in fisher 344 male rats

Synergy1, a prebiotic composed of Inulin and Oligofructose (1 : 1). Soybean meal is a natural source of isoflavones. The objective was to investigate the effects of feeding Synergy1 and SM on the incidence of azoxymethane- (AOM-) induced aberrant crypt foci (ACF) in Fisher 344 male rats. Rats (54) were randomly assigned to 9 groups (n = 6). Control group (C) was fed AIN-93G and treatment groups Syn1 and SM at 5% and 10% singly and in combinations. Rats were injected with two s/c injections of AOM at 7 and 8 weeks of age at 16 mg/kg body weight and killed at 17 weeks by CO₂ asphyxiation. Colonic ACF enumeration and hepatic enzyme activities were measured. Reductions (%) in total ACF among treatment groups fed combinations were higher (67–77) compared to groups fed singly (52–64). Synergistic mechanisms among phytochemicals may be responsible suggesting protective role in colon carcinogenesis with implications in food product development.

Supplementation of cheonggukjang and red ginseng cheonggukjang can improve plasma lipid profile and fasting blood glucose concentration in subjects with impaired fasting glucose

This study was conducted to investigate the plasma lipid profile and blood glucose-lowering effects of cheonggukjang (CH) and red ginseng CH (RGCH) in 45 subjects (men:women = 27:18; mean age, 44.9 ± 3.1 years) with impaired fasting glucose (IFG). Subjects were randomly divided into three groups: control (starch, 2 g/day), CH (20 g/day), and RGCH (20 g/day). Each volunteer received his or her daily doses for 8 weeks. The supplementation with CH and RGCH significantly decreased the plasma total cholesterol about 30.0 mg/mL and 37.7 mg/mL, respectively, compared to the initial value. The plasma low-density lipoprotein-cholesterol concentration was also significantly reduced by 29.66% and 23.42% in the CH and RGCH groups, respectively, compared to the initial value. The concentration of plasma non-high-density lipoprotein-cholesterol (107.9 mg/mL) was significantly lowered in the RGCH group compared to the initial value (139.1 mg/mL). The level of erythrocyte thiobarbituric acid-reactive substances was significantly lowered in the CH (6.5 nmol/mL) and RGCH (6.6 nmol/mL) groups compared to the initial value (7.9 nmol/mL and 8.0 nmol/mL, respectively). The ratio of apolipoprotein B and apolipoprotein A-1 concentrations (2.5) was significantly reduced in the CH group compared to the initial value (3.0). The concentration of fasting blood glucose (FBG) was significantly lower in the CH- and RGCH-supplemented groups compared to the initial value. These results suggest that CH and RGCH can lower the FBG concentration and improve the plasma lipid profile in subjects with IFG.

Soybean supplementation helps reverse age- and scopolamine-induced memory deficits in mice

Phytoestrogens are nonsteroidal plant compounds that are able to exert estrogenic effects. Soybean is a rich source of phytoestrogens, especially isoflavones. Soy isoflavones are utilized for estrogen replacement therapy. Estrogen is reported to influence several areas of brain that are involved in cognition and behavior. Therefore, the present study was undertaken to examine whether dietary supplementation with soybean improves the cognitive function of mice. Soybean was administered in three different concentrations (2%, 5% and 10% [wt/wt]) in the normal diet to young and mature mice for 60 successive days. The passive avoidance paradigm and the elevated plus maze served as the exteroceptive behavioral models, whereas scopolamine (1.4 mg/kg, i.p.) served as the interoceptive behavioral model. The brain acetylcholinesterase activity (AChE) activity, brain thiobarbituric acid-reactive substances (TBARS), reduced glutathione (GSH), and total blood cholesterol levels were also measured in the present study. The administration of soybean for 60 consecutive days protected (P < .05) the animals from developing memory impairment. Soybean administration also resulted in diminished brain AChE activity, decrease in brain TBARS, and increase in GSH levels, thereby indicating facilitated cholinergic transmission, reduced free radical generation, and enhanced scavenging of free radicals. Thus, soybean appears to be a useful remedy for improving memory and for the management of cognitive deficits owing to its pro-estrogenic, antioxidant, procholinergic, and/or neuroprotective properties.

Non-isoflavone phytochemicals in soy and their health effects

Epidemiological and clinical studies have linked consumption of soy foods with low incidences of a number of chronic diseases, such as cardiovascular diseases, cancer, and osteoporosis. Over the past decades, enormous research efforts have been made to identify bioactive components in soy. Isoflavones and soy protein have been suggested as the major bioactive components in soy and have received considerable attention. However, there are hundreds of phytochemical components in soybeans and soy-based foods. In recent years, accumulating evidence has suggested that the isoflavones or soy proteins stripped of phytochemicals only reflect certain aspects of health effects associated with soy consumption. Other phytochemicals, either alone or in combination with isoflavones or soy protein, may be involved in the health effects of soy. This review attempts to summarize major non-isoflavone phytochemicals in soy, as well as their bioavailability and health effects. In addition, a brief discussion of components formed during food processing is also included.

Exogenous gibberellic acid reprograms soybean to higher growth and salt stress tolerance

The agricultural industry is severely affected by salinity due to its high magnitude of adverse impacts and worldwide distribution. We observed the role of exogenous gibberellic acid (GA(3)) in salinity alleviation of soybean. We found that GA(3) application significantly promoted plant length and plant fresh/dry biomass while markedly hindered by NaCl induced salt stress. The adverse effect of salt stress was mitigated by GA(3), as growth attributes significantly recovered, when GA(3) was added to salt stressed soybean plants. Elevated GA(3) treatments increased daidzein and genistein contents (commonly known as phytoestrogens) of soybean leaves under control and salt stress conditions. Phytohormonal analysis of soybean showed that the level of bioactive gibberellins (GA(1) and GA(4)) and jasmonic acid increased in GA(3) treated plants, while the endogenous abscisic acid and salicylic acid contents declined under the same treatment. GA(3) mitigated the adverse effects of salt stress by regulating the level of phytohormones, thus aiding the plant in resuming its normal growth and development. The presence of GA(1) and GA(4) showed that both early-C13-hydroxylation and non-C13-hydroxylation pathways of GA biosynthesis are functional in soybean. It was concluded that GA(3) ameliorates the adverse effects of salt stress and restores normal growth and development of soybean.

Effect of dietary soy intake on breast cancer risk according to menopause and hormone receptor status

BACKGROUND

Although high soy consumption may be associated with lower breast cancer risk in Asian populations, findings from epidemiological studies have been inconsistent.

OBJECTIVE

We investigated the effects of soy intake on breast cancer risk among Korean women according to their menopausal and hormone receptor status.

METHODS

We conducted a case-control study with 358 incident breast cancer patients and 360 age-matched controls with no history of malignant neoplasm. Dietary consumption of soy products was examined using a 103-item food frequency questionnaire.

RESULTS

The estimated mean intakes of total soy and isoflavones from this study population were 76.5 g per day and 15.0 mg per day, respectively. Using a multivariate logistic regression model, we found a significant inverse association between soy intake and breast cancer risk, with a dose-response relationship (odds ratios (OR) (95% confidence interval (CI)) for the highest vs the lowest intake quartile: 0.36 (0.20-0.64)). When the data were stratified by menopausal status, the protective effect was observed only among postmenopausal women (OR (95% CI) for the highest vs the lowest intake quartile: 0.08 (0.03-0.22)). The association between soy and breast cancer risk did not differ according to estrogen receptor (ER)/progesterone receptor (PR) status, but the estimated intake of soy isoflavones showed an inverse association only among postmenopausal women with ER+/PR+ tumors.

CONCLUSIONS

Our findings suggest that high consumption of soy might be related to lower risk of breast cancer and that the effect of soy intake could vary depending on several factors.

Extraction methods determine the antioxidant capacity and induction of quinone reductase by soy products in vitro

Gastrointestinal (GI) mimic and organic solvent extracts of whole soybean powder (WSP), soy protein concentrate (SPC), and soy protein isolate (SPI) as well as soy isoflavone concentrate (SIC) were analyzed for total phenols; quinone reductase (QR) induction in hepa1c1c7 cells; antioxidant scavenging of DPPH, HOCl, ONOO(-), and O(2) (-.); and total antioxidant capacity via FRAP and ORAC assays. GI extracts of all the soy products had higher concentrations of total phenols than from acidified methanol (MeOH) but lower antioxidant potency. The MeOH extract of SPC was most potent in quenching HOCl and ONOO(-) and increasing FRAP and ORAC, but did not induce QR. Despite weak antioxidant activity, hexane (HX) extracts induced QR more than GI and MeOH extracts with WSP > SPC > SPI > IC. Soy extracts were ineffective scavengers of DPPH and O(2) (-.). Thus, extraction methods markedly affect the antioxidant profile and QR induction capacity of soy products.

Soy isoflavones and virus infections

Isoflavones and their related flavonoid compounds exert antiviral properties in vitro and in vivo against a wide range of viruses. Genistein is, by far, the most studied soy isoflavone in this regard, and it has been shown to inhibit the infectivity of enveloped or nonenveloped viruses, as well as single-stranded or double-stranded RNA or DNA viruses. At concentrations ranging from physiological to supraphysiological (3.7-370 muM), flavonoids, including genistein, have been shown to reduce the infectivity of a variety of viruses affecting humans and animals, including adenovirus, herpes simplex virus, human immunodeficiency virus, porcine reproductive and respiratory syndrome virus, and rotavirus. Although the biological properties of the flavonoids are well studied, the mechanisms of action underlying their antiviral properties have not been fully elucidated. Current results suggest a combination of effects on both the virus and the host cell. Isoflavones have been reported to affect virus binding, entry, replication, viral protein translation and formation of certain virus envelope glycoprotein complexes. Isoflavones also affect a variety of host cell signaling processes, including induction of gene transcription factors and secretion of cytokines. The efficacy of isoflavones and related flavonoids in virus infectivity in in vitro bioassays is dependent on the dose, frequency of administration and combination of isoflavones used. Despite promising in vitro results, there is lack of data confirming the in vivo efficacy of soy isoflavones. Thus, investigations using appropriate in vivo virus infectivity models to examine pharmacological and especially physiological doses of flavonoids are warranted.

Isoflavonoid content of Hong Kong soy foods

Progress in understanding the effects of dietary soy isoflavones on chronic disease prevention in the Hong Kong Chinese population has been hampered by the lack of a comprehensive soy isoflavone database. In this study, we determined the concentrations and distribution of isoflavones in 47 foods included in a soy food frequency questionnaire by reverse-phase HPLC. Results indicated that most soy products contained isoflavones ranging from 1 mg of aglucon equivalents/100 g of wet weight (bean strip noodle and egg bean curd) to 80 mg of aglucon equivalents/100 g of wet weight (oyster sauce soybean and sweet bean curd sheet). Among our food groups, mean isoflavone concentrations were lowest in the soy milk group (9.99 mg of aglucon equivalents/100 g of wet weight) and highest in the bean curd skin group (40 mg of aglucon equivalents/100 g of wet weight). The conjugation patterns of isoflavones varied within and between food groups as influenced by the types of soybeans and the processing or cooking techniques used. The isoflavone concentrations reported herein will be useful for ascertaining the relationship between exposure to dietary soy isoflavones and health effects in the Chinese population.

Dietary soy isoflavones increase insulin secretion and prevent the development of diabetic cataracts in streptozotocin-induced diabetic rats

Soy isoflavone-containing diets have been reported to be beneficial in diabetes. This present study investigated the hypoglycemic effects of isoflavones in streptozotocin (STZ)-induced diabetes. Diabetes was induced in male Sprague-Dawley rats by intraperitoneal injection of 100 mg/kg STZ. Diabetic rats were then randomly divided into 3 groups and received a special diet supplemented with casein (control), low-isoflavone soy (LIS) protein, and high-isoflavone soy protein (HIS) for 8 weeks. Compared with the control or LIS groups, those rats on the HIS diet had significantly increased body weight and serum insulin levels and reduced serum glucose and methylglyoxal levels. Serum glutathione levels were also increased in rats given the HIS diet compared with those in the control or LIS (P < .01). Serum high-density lipoprotein cholesterol level was significantly higher in HIS-fed rats than that of the control or LIS rats (P < .05). More importantly, the death rate and incidence of cataracts in the diabetic rats were markedly decreased in the HIS group. In conclusion, ingestion of high-isoflavone soy protein not only lowers glucose levels but also reduces the incidence of cataracts in diabetic rats. The beneficial effects of soy isoflavones are attributed to increased insulin secretion, a better glycemic control, and antioxidant protection.

Soy isoflavones attenuate oxidative stress and improve parameters related to aging and Alzheimer's disease in C57BL/6J mice treated with D-galactose

d-galactose (DG)-induced aging in C57BL/6J (B6) mice (3-4 mo) was used to examine the effects of soy isoflavones (SIF). Mice were divided into six groups: corn oil control, DG treatment, DG+melatonin (1 mg/kg BW), and DG+low (0.1 mg/kg), median (0.5 mg/kg) or high (2.5 mg/kg) SIF. DG was administered (s.c., 0.3 mL of 1% solution/mouse) daily for 50 days, during which melatonin and SIF were given (p.o.) 5 d/wk. A 7th group of B6 mice (11 mo) served as natural aging (NA) control, which received neither DG nor other treatments. DG significantly increased: (1) thiobarbituric acid-reactive substances in serum and brain; (2) protein carbonyls in liver, kidney and brain; (3) soluble extracellular receptors for advanced glycation end products in serum; (4) expression of Bax and caspase-3 proteins in splenocytes; (5) protein expression of Abeta, presenilin-1 and beta-site amyloid precursor protein cleaving enzyme-1 in brain. SIF significantly attenuated DG-induced changes, with high SIF completely reversing most of these changes. The DG treatment group and the NA group had similar changes in most of the parameters measured. Overall, this DG-mimetic aging study shows that SIF effectively attenuate oxidative damage and improve parameters related to aging and Alzheimer's disease.

Dietary intake of soy protein and tofu in association with breast cancer risk based on a case-control study

Soy food and its constituents may protect against breast cancer, but the association between soy intake and decreased breast cancer risk is inconsistent. We evaluated the relationship between breast cancer risk and the dietary intake of soy protein as measured by total soy food and tofu intake. Histologically confirmed cases (n = 362) were matched to controls by age (within 2 yr) and menopausal status. High soy protein intake was associated with reduced breast cancer risk in analyses adjusted for potential confounders including dietary factors among premenopausal women (odds ratio [OR] = 0.39 in the highest quintile, 95% confidence interval [CI] = 0.22-0.93, P for trend = 0.03) and postmenopausal women (OR = 0.22, 95% CI = 0.06-0.88, P for trend = 0.16). We also found an inverse association between total tofu intake and breast cancer risk among premenopausal women (for total tofu intake, OR = 0.23 in the highest quintile, 95% CI = 0.11-0.48, P for trend < 0.01; for at least 1 serving of tofu as the main ingredient per day, OR = 0.26, 95% CI = 0.13-0.55, P for trend < 0.01). We concluded that increased regular soy food intake at a level equivalent to traditional Korean consumption levels may be associated with a reduced risk of breast cancer, and this effect is more pronounced in premenopausal women.

Bowman-Birk inhibitor and genistein among soy compounds that synergistically inhibit nitric oxide and prostaglandin E2 pathways in lipopolysaccharide-induced macrophages

Inflammation has an important role in the development of chronic diseases. In this study, we evaluated the anti-inflammatory properties of eight soybean bioactive compounds using lipopolysaccharide-induced RAW 264.7 macrophages. Genistein, daidzein, a mix of isoflavone glucosides, saponin A group glycosides (saponin A), saponin B group glycosides (saponin B), sapogenol B, Bowman-Birk inhibitor (BBI), lunasin, and pepsin-pancreatin glycinin hydrolysates were tested by measuring their ability to inhibit cyclooxygenase-2/prostaglandin E(2) (PGE(2)) and inducible nitric oxide synthase (iNOS)/nitric oxide (NO) inflammatory pathways. Of the eight soy bioactive compounds (SBCs) tested, BBI and sapogenol B resulted in the highest inhibition of pro-inflammatory responses at a concentration 10 times lower than the one used for the other compounds. Also, sapogenol B and genistein (molar ratio 1:1) synergistically inhibited NO and additively inhibited PGE(2). Saponin A group glycosides showed inhibition of the iNOS/NO pathway only, while pepsin-pancreatin glycinin hydrolysates enhanced induction and production of the four inflammatory responses. For the first time, synergistic interactions were observed between BBI and genistein inhibiting NO (92.7%) and PGE(2) (95.6%) production. An antagonistic interaction was observed between the saponin B group glycosides and sapogenol B. All interactions were further confirmed by isobolographic analysis. These findings demonstrated that some SBCs possess anti-inflammatory properties and therefore are important in modulating mammalian inflammation pathways which may lead to inhibition of some types of chronic disease. Furthermore, through their interaction they can modulate the inflammatory process.

Phenolic derivatives from soy flour ethanol extract are potent in vitro quinone reductase (QR) inducing agents

The fractionation of soy flour directed by a cellular bioassay for induction of phase 2 detoxification enzymes was used to identify quinone reductase (QR) inducing agents. A phospholipid-depleted, 80% methanol-partitioned isolate from a crude ethanol extract of soy flour was resolved using normal phase medium-pressure liquid chromatography (MPLC). Early eluting fractions were found to be the most potent QR inducing agents among the separated fractions. Fraction 2 was the most potent, doubling QR at <2 mug/mL. Further fractionation of this isolate led to the identification of several constituents. Fatty acids and sn-1 and sn-2 monoacylglycerols were identified, but were not highly potent QR inducers. Benzofuran-3-carbaldehyde, 4-hydroxybenzaldeyde, 4-ethoxybenzoic acid, 4-ethoxycinnamic acid, benzofuran-2-carboxylic ethyl ester, and ferulic acid ethyl ester (FAEE) were also identified as QR inducing constituents of this fraction. FAEE was the most potent of the identified constituents, doubling QR specific activity at 3.2 muM in the cellular bioassay.

Effects of light treatment on isoflavone content of germinated soybean seeds

Our research objective was to increase isoflavone content in the germinated soybean seeds of four different varieties (Pungsannamulkong, Cheongjakong, Aga4, and Aga3) by optimizing light treatments (dark, greenhouse, fluorescent, incandescent, and ultraviolet lamps). The results demonstrated that the highest isoflavone content was produced from the Aga3 variety, which was developed by an interspecific cross between Eunhakong (Glycine max) and KLG10084 (G. soja) at the Plant Genetic Laboratory, Kyunpook National University. Aga3 is known to have one of the highest isoflavone content in the world at present. Our results recommend exposure of 7-day-old Aga3 sprouts to a combined light treatment of greenhouse lamps (12 h per day) and ultraviolet light (40 min per day) for maximum isoflavone production. Aga3 produced high levels of isoflavone because, in part, it contained very high isoflavone levels within the seed as compared with the other varieties. Under stress conditions, Aga3 could produce over 1.90 times more isoflavone than its seed content and 1.53 times more isoflavone than when grown under dark conditions.

A very-low-fat vegan diet increases intake of protective dietary factors and decreases intake of pathogenic dietary factors

There is increasing evidence that dietary factors in plant-based diets are important in the prevention of chronic disease. This study examined protective (eg, antioxidant vitamins, carotenoids, and fiber) and pathogenic (eg, saturated fatty acids and cholesterol) dietary factors in a very-low-fat vegan diet. Ninety-three early-stage prostate cancer patients participated in a randomized controlled trial and were assigned to a very-low-fat (10% fat) vegan diet supplemented with soy protein and lifestyle changes or to usual care. Three-day food records were collected at baseline (n=42 intervention, n=43 control) and after 1 year (n=37 in each group). Analyses of changes in dietary intake of macronutrients, vitamins, minerals, carotenoids, and isoflavones from baseline to 1 year showed significantly increased intake of most protective dietary factors (eg, fiber increased from a mean of 31 to 59 g/day, lycopene increased from 8,693 to 34,464 mug/day) and significantly decreased intake of most pathogenic dietary factors (eg, saturated fatty acids decreased from 20 to 5 g/day, cholesterol decreased from 200 to 10 mg/day) in the intervention group compared to controls. These results suggest that a very-low-fat vegan diet can be useful in increasing intake of protective nutrients and phytochemicals and minimizing intake of dietary factors implicated in several chronic diseases.

Isoflavone treatment for acute menopausal symptoms

OBJECTIVE

The onset of climacteric symptoms (hot flashes and night sweats) is the primary reason for perimenopausal women to start hormone therapy. The association of a lower incidence of postmenopausal symptoms with high intake of soybeans in Asian women suggests that phytoestrogens are an alternative to estrogen therapy. The main effective compounds in soybean are isoflavones, which have a higher binding affinity to estrogen receptor beta than to estrogen receptor alpha. The aim of present study was to evaluate the effects of isoflavone treatment in postmenopausal women.

DESIGN

This was a double-blind prospective study. Sixty healthy postmenopausal women were randomly assigned by computer into two groups to receive 60 mg isoflavones or placebo daily for 3 months. Before and after treatment, climacteric symptoms were recorded; serum was collected to measure the levels of lipoprotein lipids, estradiol, and follicle-stimulating hormone; and biopsy specimens from endometrium and breast were analyzed to investigate the expression level of steroid receptors and proliferation. Endometrial thickness was measured by ultrasound.

RESULTS

Fifty-one women finished the 12-week study. In women receiving 60 mg isoflavones daily, hot flashes and night sweats were reduced by 57% and 43%, respectively. The treatment did not change the levels of circulating estradiol or follicle-stimulating hormone. Immunohistochemical staining of endometrial and breast biopsy specimens revealed that isoflavones did not affect expression levels of steroid receptors; estrogen receptors alpha, beta, and betacx; progesterone receptors A and B; or the proliferation marker Ki67. No side effects on body weight or lipoprotein lipids were observed.

CONCLUSIONS

This short-term prospective study implies that isoflavones could be used to relieve acute menopausal symptoms.

High performance liquid chromatography and capillary electrophoresis in the analysis of soybean proteins and peptides in foodstuffs

The increasing interest in functional and healthy food products has promoted the use of soybean in the manufacture of foods for human consumption. Soybean basic products (soybeans, textured soybean, soybean flour, soybean protein concentrate and soybean protein isolate) as well as soybean derivatives (soybean dairy-like products, soybean drinks with fruits, meat analogues, etc.) are commercially available. In addition, due to the interesting nutritional and functional properties of soybean proteins, they are usually employed as ingredient in the elaboration of a large number of food products such as bakery or meat products among others. In spite of the good characteristics of soybean proteins, their addition to some products is forbidden or allowed up to a certain limit. Therefore, analytical methodologies to achieve the determination of soybean proteins in foods are necessary in order to make possible adequate quality control and to prove that legal regulations controlling their addition are accomplished. However, this is not an easy task due to the diversity and complexity of the food matrices and the technological treatments to which some of these foods are submitted during their elaboration. This article presents for the first time a comprehensive review on the analytical methodologies developed using HPLC and CE to characterize soybeans and to analyse soybean proteins in meals. Moreover, the use of HPLC and CE in the characterization of soybean protein fractions and their hydrolyzates, and a study of their relationships to nutritional, functional and biomedical properties are included. Finally, the application of proteomic methodologies in soybean food technology is also reviewed.

Long-term consumption of fermented soybean-derived Chungkookjang enhances insulinotropic action unlike soybeans in 90% pancreatectomized diabetic rats

BACKGROUND

We previously reported that Chungkookjang (CKJ), fermented unsalted soybeans, exhibited better anti-diabetic action than cooked soybeans (CSB) in vitro, but its effectiveness and mechanism have not been studied in vivo.

AIM OF THE STUDY

We investigated whether CKJ modulated insulin resistance, insulin secretion, and pancreatic beta-cell growth and survival in 90% pancreatectomized (Px) diabetic rats.

METHODS

The Px rats weighing 201 +/- 12 g were divided into four groups and fed for 8 weeks with a CSB diet, a CKJ diet, a casein diet, or a casein diet plus rosiglitazone (20 mg/kg body weight/day). With the exception of protein sources and contents of isoflavonoid aglycones and glycosides, the composition of the diets was made identical by adding soybean oil and cellulose to a casein diet. At the end of the experimental periods, hyperglycemic clamp was performed in conscious, unstressed and overnight fasted Px rats to measure insulin secretion capacity. Insulin/IGF-1 signaling was measured by immunoblotting in isolated islets from the treated rats, and beta-cell mass, proliferation and apoptosis were also determined by immunohistochemistry.

RESULTS

After 8-week administration, CSB did not modulate glucose-stimulated insulin secretion, but surprisingly, CKJ enhanced insulin secretion. In addition, CKJ potentiated insulin/IGF-1 signaling in islets via the induction of insulin receptor substrate-2 expression, leading to increasing pancreatic duodenal homeobox-1, insulin promoter transcription factor. In parallel with the enhancement of the signaling, CKJ elevated pancreatic beta-cell hyperplasia by increasing its proliferation and decreasing apoptosis, whereas CSB did not.

CONCLUSION

Based on these results, the fermentation of soybeans predominantly with Bacillus subtilis generated isoflavonoid aglycones and small peptides, which improved insulinotropic action in islets of type 2 diabetic rats. Overall, the anti-diabetic action of CKJ was superior to CSB in type 2 diabetic rats.

A combination of soy isoflavone supplementation and exercise improves lipid profiles and protects antioxidant defense-systems against exercise-induced oxidative stress in ovariectomized rats

Menopause is often accompanied with weight gain, metabolic lipid abnormalities, and oxidative stress. In this study, we investigated the combined effects of exercise and soy isoflavone supplementation on the lipid profiles and antioxidant capacities of ovariectomized rats. Twenty-five female Sprague-Dawley rats were divided into 5 groups: sham-operated, ovariectomized (OVX), OVX with exercise (OVX+EX), OVX with soy isoflavone supplementation (OVX+ISO), and OVX with both soy isoflavones and exercise (OVX+ISO+EX). After 12 weeks of intervention, antioxidant status was evaluated in collected blood samples by the ferric reducing ability of plasma (FRAP), glutathione (GSH) content, and sodium oxide dismutase (SOD) activity. DNA damage in the lymphocytes was determined using alkaline single-cell gel electrophoresis (the Comet assay). Although there were no significant differences in weight gain and food intake, weight gain was lower in OVX+EX, OVX+ISO, and OVX+ISO+EX than in OVX. OVX+EX, OVX+ISO, and OVX+ ISO+EX showed a significant decrease in total cholesterol, triglycerides, and LDL-cholesterol compared to OVX. The soy isoflavone supplemented group had significantly increased FRAP values and GSH contents in contrast to no changes in the exercised group, whereas exercise markedly increased SOD activity and H2O2-induced DNA tail length and tail moment. Exercise with soy isoflavone supplementation significantly increased FRAP values and had no difference on SOD activity, including DNA damage. These results demonstrate that a combined treatment of moderate exercise and soy isoflavone supplementation could exert a beneficial effect on weight control and lipid profiles, and offer protection from exercise-induced oxidative stress in postmenopausal women.

Activation of glutathione peroxidase via Nrf1 mediates genistein’s protection against oxidative endothelial cell injury

Cellular actions of isoflavones may mediate the beneficial health effects associated with high soy consumption. We have investigated protection by genistein and daidzein against oxidative stress-induced endothelial injury. Genistein but not daidzein protected endothelial cells from damage induced by oxidative stress. This protection was accompanied by decreases in intracellular glutathione levels that could be explained by the generation of glutathionyl conjugates of the oxidised genistein metabolite, 5,7,3',4'-tetrahydroxyisoflavone. Both isoflavones evoked increased protein expression of gamma-glutamylcysteine synthetase-heavy subunit (gamma-GCS-HS) and increased cytosolic accumulation and nuclear translocation of Nrf2. However, only genistein led to increases in the cytosolic accumulation and nuclear translocation of Nrf1 and the increased expression of and activity of glutathione peroxidase. These results suggest that genistein-induced protective effects depend primarily on the activation of glutathione peroxidase mediated by Nrf1 activation, and not on Nrf2 activation or increases in glutathione synthesis.

Both soybean and kudzu phytoestrogens modify favorably the blood lipoprotein profile in ovariectomized and castrated hamsters

The present study compared the hypolipidemic activity of kudzu phytoestrogens with that of soybean phytoestrogen in estrogen- and androgen-deficient hamsters. In the first experiment, ovariectomized hamsters (n = 37) were randomly divided into four groups (n = 9-10 each group). The first group was the control group, whereas the second group had the time-releasing estradiol-17beta subcutaneous (pellet) implants as a positive control. The third and fourth groups were orally administered soybean or kudzu phytoestrogen extracts (30 mg/kg of body weight) per day. In the second experiments, the first group of male hamsters (n = 9) received a sham operation, whereas the other three groups of male hamsters (n = 9 each) were castrated. The castrated control group received orally distilled water, whereas the second and third castrated groups were orally given 30 mg/kg soybean or kudzu phytoestrogen extracts. The results for the first experiment showed that the ovariectomized hamsters orally given soybean and kudzu phytoestrogen extracts had significantly decreased serum total cholesterol (TC) and non-high-density lipoprotein cholesterol (non-HDL-C) with HDL cholesterol (HDL-C) being unaffected. The data from the second experiment demonstrated that administration of soybean but not kudzu phytoestrogen extracts decreased significantly serum TC. However, administration of kudzu phytoestrogens caused redistribution of cholesterol among lipoproteins, leading to a significant decrease in the ratio of non-HDL-C to HDL-C. It was concluded that both soybean and kudzu phytoestrogens could modify favorably lipoprotein profiles in ovariectomized and castrated hamsters.