Soybean Isoflavones Research Articles

Inhibitory Effect of Isoflavones from Processed Soybeans on Human DNA Topoisomerase II Activity

In this study, we found that the amount of isoflavones in (1) steaming germinated soybean was higher than that of (2) soybean boiled in water and (3) steamed soybean. Moreover, genistein, a major soy isoflavone, selectively inhibited the activity of human topo II. Therefore, steaming germinated soybean, which has high amount of genistein, might be a cancer preventive food through the inhibition of topo II activity.

Preparation and characterization of fine powdered whole soybean curd.

[Purpose]Efficacy and comparative characteristics of fine powdered whole soybean curd.[Methods]Ground dried soybean to a fine powder (700 mesh) containing bean components in its entirety, and then produced whole soybean curd. Analysed its nutritive components, bioactive substances, antioxidant activities and texture compared with pressed soybean curd.[Results]Compared with pressed soybean curd, the nutrients and isoflavone in whole soybean curd were slightly decreased, but antioxidant activities, dietary fibers and moisture content were increased. Also, the yield rate of the total process was improved 1.9 times.[Conclusion]Fine powdered whole bean curd has antioxidant effects, contains dietary fiber and possesses soft characteristics, hence has development potential in the diet market and as food for patients.

Equol-induces apoptosis in chemoresistant ovarian cancer cells via external pathway

<p>Polyphenolic compounds present in fruits, vegetables and grains are bioactive molecules which elicit a wide range of responses both in vivo and in vitro. The aim of this study was to investigate whether the soybean isoflavone Equol could induce apoptosis in ovarian cancer cells. In this study, we evaluated molecular events associated with apoptosis induced by Equol and paclitaxel (PTX) in an ovarian cancer cell line SKOV-3. To assess whether growth inhibition was due to apoptosis, flow cytometry, colorimetry experiments, immunoblot analyses through measuring DNA fragmentation, the level of TRAIL,the cleavage of poly(ADP-ribose) polymerase (PARP) and the activation of caspase-3, -8 and -9 were also performed. Additional markers of apoptosis were also measured like phosphatidylserine externalization and morphological changes. In addition, glycoprotein P (P-gp) activity in SKOV-3 ovarian cancer cell line was also estimated. The experimental results showed that apoptosis was induced by extrinsic pathway triggered by certain TNF family members. Overall results suggested that Equol induces apoptosis in SKOV-3 cells via a TRAIL and caspase 8-dependent pathway whereas paclitaxel leads to smaller apoptotic events when compared to that of Equol.</p>

Synergistic Effects of Dietary Natural Products as Anti-Prostate Cancer Agents

This review is to describe synergistic effects of various combinations of dietary natural products including curcumin, quercetin, soybean isoflavones, silibinin, and EGCG that have potential for the treatment of prostate cancer. These data can provide valuable insights into the future rational design and development of synergistic and/or hybrid agents for potential treatment of prostate cancer.

Pre-treatment with calcium enhanced defense-related genes' expression in the soybean's isoflavones pathway in response to Sclerotinia sclerotiorum

Sclerotinia sclerotiorum (Lib.) de Bary is a fungal plant that causes serious losses in important crops. This study examined the expression of selected defense-related genes in the isoflavonoids pathway after soybean inoculation with two Sclerotinia isolates possessing different levels of aggressiveness (SSPetri, highly aggressive and SS18, weakly aggressive) and the effects of pre-treatment with calcium on disease symptoms. PAL1 displayed an early expression after inoculation regardless of the isolate used. Expression of IFS2 and IFR2 were more pronounced in leaves inoculated with the weakly aggressive isolate SS18 than with its highly aggressive counterpart. Oppositely, CHS3, CHS5 and CHI1B1–CHI1B2 had higher transcript abundance in presence of the highly aggressive isolate SSPetri. Pre-treatment with calcium enhanced the expression of CHS3, CHS5, CHI1B1–CHI1B2 IFS2 and IFR2 in the leaves inoculated with SSPetri. An increase in isoflavone aglycones and their malonyl and acetyl conjugates was recorded in the inoculated leaves, with higher contents in response to SSPetri. Pre-treatment with calcium improved the accumulation of daidzein, genistein and acetyl glycitin, especially in the leaves inoculated with SSPetri. De novo synthesis of glyceollins occurred in response to inoculation, especially in response to the highly aggressive isolate SSPetri.

Overexpression of Soybean Isoflavone Reductase (GmIFR) Enhances Resistance to Phytophthora sojae in Soybean.

Isoflavone reductase (IFR) is an enzyme involved in the biosynthetic pathway of isoflavonoid phytoalexin in plants. IFRs are unique to the plant kingdom and are considered to have crucial roles in plant response to various biotic and abiotic environmental stresses. Here, we report the characterization of a novel member of the soybean isoflavone reductase gene family GmIFR. Overexpression of GmIFR transgenic soybean exhibited enhanced resistance to Phytophthora sojae. Following stress treatments, GmIFR was significantly induced by P. sojae, ethephon (ET), abscisic acid (placeCityABA), salicylic acid (SA). It is located in the cytoplasm when transiently expressed in soybean protoplasts. The daidzein levels reduced greatly for the seeds of transgenic plants, while the relative content of glyceollins in transgenic plants was significantly higher than that of non-transgenic plants. Furthermore, we found that the relative expression levels of reactive oxygen species (ROS) of transgenic soybean plants were significantly lower than those of non-transgenic plants after incubation with P. sojae, suggesting an important role of GmIFR might function as an antioxidant to reduce ROS in soybean. The enzyme activity assay suggested that GmIFR has isoflavone reductase activity.

Heterologous expression of a GH3 β-glucosidase from Neurospora crassa in Pichia pastoris with high purity and its application in the hydrolysis of soybean isoflavone glycosides

Previous studies have shown isoflavone aglycones to have more biological effects than their counterparts, isoflavone glycones. Some β-glucosidases can hydrolyze isoflavone glucosides to release aglycones, and discovery of these has attracted great interest. A glycoside hydrolase (GH) family 3 β-glucosidase (bgl2) gene from Neurospora crassa was heterologously expressed in Pichia pastoris with high purity. The recombinant BGL2 enzyme displayed its highest activity at pH 5.0 and 60 °C, and had its maximum activity against p-nitrophenyl-β-d-glucopyranoside (pNPG) (143.27 ± 4.79 U/mg), followed by cellobiose (74.99 ± 0.78 U/mg), gentiobiose (47.55 ± 0.15 U/mg), p-nitrophenyl-β-d-cellobioside (pNPC) (40.07 ± 0.87 U/mg), cellotriose (12.31 ± 0.36 U/mg) and cellotetraose (9.04 ± 0.14 U/mg). The kinetic parameters of Km and Vmax were 0.21 ± 0.01 mM and 147.93 ± 2.77 μM/mg/min for pNPG. The purified enzyme showed a heightened ability to convert the major soybean isoflavone glycosides (daidzin, genistin and glycitin) into their corresponding aglycone forms (daidzien, genistein and glycitein). With this activity against soybean isoflavone glycosides, BGL2 shows great potential for applications in the food, animal feed, and pharmaceutical industries.

Induction of proto-oncogene BRF2 in breast cancer cells by the dietary soybean isoflavone daidzein.

BackgroundBRF2 is a transcription factor required for synthesis of a small group of non-coding RNAs by RNA polymerase III. Overexpression of BRF2 can transform human mammary epithelial cells. In both breast and lung cancers, the BRF2 gene is amplified and overexpressed and may serve as an oncogenic driver. Furthermore, elevated BRF2 can be independently prognostic of unfavorable survival. Dietary soy isoflavones increase metastasis to lungs in a model of breast cancer and a recent study reported significantly increased cell proliferation in breast cancer patients who used soy supplementation. The soy isoflavone daidzein is a major food-derived phytoestrogen that is structurally similar to estrogen. The putative estrogenic effect of soy raises concern that high consumption of soy foods by breast cancer patients may increase tumor growth.MethodsExpression of BRF2 RNA and protein was assayed in ER-positive or –negative human breast cancer cells after exposure to daidzein. We also measured mRNA stability, promoter methylation and response to the demethylating agent 5-azacytidine. In addition, expression was compared between mice fed diets enriched or deprived of isoflavones.ResultsWe demonstrate that the soy isoflavone daidzein specifically stimulates expression of BRF2 in ER-positive breast cancer cells, as well as the related factor BRF1. Induction is accompanied by increased levels of non-coding RNAs that are regulated by BRF2 and BRF1. Daidzein treatment stabilizes BRF2 and BRF1 mRNAs and selectively decreases methylation of the BRF2 promoter. Functional significance of demethylation is supported by induction of BRF2 by the methyltransferase inhibitor 5-azacytidine. None of these effects are observed in an ER-negative breast cancer line, when tested in parallel with ER-positive breast cancer cells. In vivo relevance is suggested by the significantly elevated levels of BRF2 mRNA detected in female mice fed a high-isoflavone commercial diet. In striking contrast, BRF2 and BRF1 mRNA levels are suppressed in matched male mice fed the same isoflavone-enriched diet.ConclusionsThe BRF2 gene that is implicated in cancer can be induced in human breast cancer cells by the isoflavone daidzein, through promoter demethylation and/or mRNA stabilization. Dietary isoflavones may also induce BRF2 in female mice, whereas the converse occurs in males.

Soybean and tempeh total isoflavones improved antioxidant activities in normal and scopolamine-induced rat brain

Soybean and tempeh total isoflavones improved antioxidant activities in normal and scopolamine-induced rat brain

Effects of dietary soybean isoflavones on non-specific immune responses and hepatic antioxidant abilities and mRNA expression of two heat shock proteins (HSPs) in juvenile golden pompano Trachinotus ovatus under pH stress.

This study determined the effect of dietary soybean isoflavones on non-specific immunity and on mRNA expression of two HSPs in juvenile golden pompano Trachinotus ovatus under pH stress. Six diets were formulated to contain 0, 10, 20, 40, 60 and 80 mg/kg of soybean isoflavones. Each diet was fed to triplicate groups of fish in cylindrical tanks. After 56 days of feeding, 15 fish per tank were exposed to pH stress (pH ≈ 9.2) for 24 h. Serum total protein (TP), respiratory burst activity (RBA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), lysozyme (LYZ), complement 3 (C3), complement 4 (C4), cortisol, hepatic total antioxidant capacity (T-AOC), superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT) and the relative mRNA expression of heat shock protein 70 (HSP70) and 90 (HSP90) were investigated. The results showed that after pH stress, serum TP, RBA, LYZ, C4, hepatic T-AOC and CAT levels were significantly reduced (P < 0.05) while serum ALT, hepatic MDA and HSP70 and HSP90 mRNA expression levels were significantly increased (P < 0.05). On the other hand, supplementation with soybean isoflavones significantly reduced levels of serum ALT (20, 40, 60 mg/kg soybean isoflavones groups) and hepatic MDA (40, 60 and 80 mg/kg soybean isoflavones groups). Supplemented groups had increased serum TP content (40 mg/kg soybean isoflavones groups), RBA (20 and 40 mg/kg soybean isoflavones groups), LYZ (40 and 60 mg/kg soybean isoflavones groups), C3(20, 40, 60 and 80 mg/kg soybean isoflavones groups), hepatic SOD activity (40, 60 and 80 mg/kg soybean isoflavones groups) as well as increased relative mRNA expression of hepatic HSP70 (40, 60 and 80 mg/kg soybean isoflavones groups) and HSP90 (40 and 60 mg/kg soybean isoflavones groups) (P < 0.05). These results indicate that ingestion of a basal diet supplemented with 40-60 mg/kg soybean isoflavones could enhance resistance against pH stress in T. Ovatus to some degree.

Hyaluronic acid concentration of diabetic rats’ vaginas treated with soybean isoflavones or 17β-estradiol

The isopranolic extract of Cimicifuga racemosa (iCR), active ingredient of the herbal medicinal product Remifemin®, is therapeutically used to relieve menopausal complaints such as hot flushes, sweating and correlated sleep disturbances. In addition, clinical studies have shown beneficial effects on the menopauseinduced depressive mood, nervousness, nervous irritability and generally impaired performance and memory. The mode of action is not yet fully understood. Eleven male rats received an implant consisting of four bipolar concentric electrodes targeting at frontal cortex, hippocampus, striatum andmidbrain reticular formation. EEG signals were recorded from these brain areas of freely moving rats (Tele-Stereo-EEG model) for 5h with and without previous treatment with iCR (7.5mg/kg). Data were evaluated by Fast Fourier Transformation (FFT) and averaged to give hourly values in % of the baseline values.iCR markedly influenced electric CNS-function and induced changesof spectral frequenciesof rat brainelectric activity. iCR caused a general attenuation of the spectral powerwithin all frequency bands and all brain areas. Strongest effects were found in frontal cortex and in hippocampus. The decrease in -2 waves (>40%) suggests an increase in dopaminergic activity, while a decrease in -1 and -1 frequencies is in line with an increase in serotonergic and glutamatergic activity, respectively. Such changes on brain activity were compared to frequency pattern changes of a large number of synthetic drugs with known therapeutic use. This data were fed into a discriminant analysis and led to clustering of drugs with similar clinical indication. Comparison to reference drugs tested in the past and making up a large data base revealed some similarity to drugs used to treat Parkinson’s disease (Selegiline), to influence moodand cognition (Ginkgo), to treat dementia (Tacrine) or to treat depression (Moclobemide). Further experiments are needed in order to gather more information on the effects of iCR extract on the brain, possibly leading to new indications for this herbal preparation with respect to mood and cognition.

Effect of Soyabean Isoflavones Exposure on Onset of Puberty, Serum Hormone Concentration and Gene Expression in Hypothalamus, Pituitary Gland and Ovary of Female Bama Miniature Pigs.

This study was to investigate the effect of soyabean isoflavones (SIF) on onset of puberty, serum hormone concentration, and gene expression in hypothalamus, pituitary and ovary of female Bama miniature pigs. Fifty five, 35-days old pigs were randomly assigned into 5 treatment groups consisting of 11 pigs per treatment. Results showed that dietary supplementation of varying dosage (0, 250, 500, and 1,250 mg/kg) of SIF induced puberty delay of the pigs with the age of puberty of pigs fed basal diet supplemented with 1,250 mg/kg SIF was significantly higher (p<0.05) compared to control. Supplementation of SIF or estradiol valerate (EV) reduced (p<0.05) serum gonadotrophin releasing hormone and luteinizing hormone concentration, but increased follicle-stimulating hormone concentration in pigs at 4 months of age. The expression of KiSS-1 metastasis-suppressor (KISS1), steroidogenic acute regulatory protein (StAR) and 3-beta-hydroxysteroid dehydrogenase/delta-5-delta-4 isomerase (3β-HSD) was reduced (p<0.01) in SIF-supplemented groups. Expression of gonadotropin-releasing hormone receptor in the pituitary of miniature pigs was reduced (p<0.05) compared to the control when exposed to 250, 1,250 mg/kg SIF and EV. Pigs on 250 mg/kg SIF and EV also showed reduced (p<0.05) expression of cytochrome P450 19A1 compared to the control. Our results indicated that dietary supplementation of SIF induced puberty delay, which may be due to down-regulation of key genes that play vital roles in the synthesis of steroid hormones.

Flt3 is a target of coumestrol in protecting against UVB-induced skin photoaging

While skin aging is a naturally occurring process by senescence, exposure to ultraviolet (UV) radiation accelerates wrinkle formation and sagging of skin. UV induces skin aging by degrading collagen via activating matrix metalloproteinases (MMPs). In this study, we show that coumestrol, a metabolite of the soybean isoflavone daidzein, has a preventive effect on skin photoaging in three-dimensional human skin equivalent model. Coumestrol inhibited UVB-induced MMP-1 expression and activity. Whole human kinase profiling assay identified FLT3 kinase as a novel target protein of coumestrol in UVB-induced signaling pathway in skin. Coumestrol suppresses FLT3 kinase activity, and subsequently, Ras/MEK/ERK and Akt/p70 ribosomal S6 kinase pathway. This suppresses AP-1 activity and in turn, diminishes MMP-1 gene transcription. Using X-ray crystallography, the binding of coumestrol to FLT3 was defined and implied ATP-competitive inhibition. Residues Lys644 and Phe830 showed local changes to accommodate coumestrol in the ATP-binding pocket. 4-APIA, a pharmacological inhibitor of FLT3, inhibited MMP-1 expression and induced signal transduction changes similar to coumestrol. Taken together, coumestrol inhibits UVB-induced MMP-1 expression by suppressing FLT3 kinase activity. These findings suggest that coumestrol is a novel dietary compound with potential application in preventing and improving UVB-associated skin aging.

Multigene synergism increases the isoflavone and proanthocyanidin contents of Medicago truncatula.

Isoflavones and proanthocyanidins (PAs), which are flavonoid derivatives, possess many health benefits and play important roles in forage-based livestock production. However, the foliage of Medicago species accumulates limited levels of both isoflavones and PAs. In this study, biosynthesis of isoflavone and PA in Medicago truncatula was enhanced via synergy between soya bean isoflavone synthase (IFS1); two upstream enzymes, chalcone synthase (CHS) and chalcone isomerase (CHI); and the endogenous flavanone 3-hydroxylase (F3H). Constitutive expression of GmIFS1 alone resulted in ectopic accumulation of the isoflavone daidzein and large increases in the levels of the isoflavones formononetin, genistein and biochanin A in the leaves. Furthermore, coexpression of GmIFS1 with GmCHS7 and GmCHI1A generally increased the available flux to flavonoid biosynthesis and resulted in elevated isoflavone, flavone and PA contents. In addition, down-regulation of MtF3H combined with coexpression of GmIFS1, GmCHS7 and GmCHI1A led to the highest isoflavone levels (up to 2 μmol/g fresh weight in total). Taken together, our results demonstrate that multigene synergism is a powerful means to enhance the biosynthesis of particular flavonoids and can be more broadly applied to the metabolic engineering of forage species.

The effects of isoflavones on lipid profile and oxidative stress in diabetic rats

Objective To investigate the effects of soybean isoflavone(SI) regulating plasma lipid and improving antioxidant ability in diabetic rats. Methods 120 SD rats were randomly devided into a normal group, a diabetes model group, a SI 40, 80, 160 and 320 mg/kg treated group, with 20 expermental animals in each group. Expect the normal group, the diabetic model was setup by intraperitoneal injecting STZ, and the drugs were given by intraperitoneal injection. At 0, 14, 28, 42, 56 days after experiment, the level of plasma glucose were determined. 8 weeks later, the content of TC, TG, LDL-C, HDL-C, the activity of AST, CK, LDH and the T-AOC in serum were determined; the activity of SOD, GSH-Px and the content of MDA in myocardial tissue were determined; and the histopathological changes of myocardial tissue were observed by HE staining. Results Compared with the diabetes model control group, the activity of AST in serum of SI 80, 160 and 320 mg/kg treated groups were significantly decreased(104.25 ± 24.92 U/L, 93.71 ± 22.58 U/L, 88.26 ± 23.80 U/L vs. 127.65 ± 38.17 U/L; P<0.05, P<0.01), the activity of CK were significantly decreased (887.1 ± 185.4 U/L, 831.9 ± 182.8 U/L, 796.2 ± 165.8 U/L vs. 973.6 ± 211.4 U/L; P<0.05, P<0.01), the activity of LDH were significantly decreased (954.7 ± 153.5 U/L, 868.7 ± 136.2 U/L, 834.1 ± 146.3 U/L vs. 1 097.6 ± 184.2 U/L; P<0.05, P<0.01); the activity of SOD in myocardial tissue were significantly increased(9.96 ± 2.05 U/mg, 10.47 ± 2.32 U/mg, 11.06 ± 2.29 U/mg vs. 8.72 ± 1.70 U/mg; P<0.05, P<0.01), the content of MDA in myocardial tissue were significantly decreased(5.98 ± 1.35 nmol/mg, 5.47 ± 1.42 nmol/mg, 5.16 ± 1.53 nmol/mg vs. 6.58 ± 1.54 nmol/mg; P<0.05, P<0.01). The plasma glucose level of SI (160 and 320 mg/kg) treated groups were significantly decreased(15.2 ± 0.9 mmol/L, 14.8 ± 0.8 mmol/L vs. 18.6 ± 1.2 mmol/L; P<0.05, P<0.01), the content of TC in serum were significantly decreased (2.69 ± 0.85 mmol/L, 2.43 ± 0.76 mmol/L vs. 3.42 ± 0.81 mmol/L; P<0.05, P<0.01), the content of TG were significantly decreased (1.36 ± 0.40 mmol/L, 1.18 ± 0.23 mmol/L vs. 1.70 ± 0.53 mmol/L; P<0.05, P<0.01), the content of LDL-C were significantly decreased (1.02 ± 0.26 mmol/L, 0.95 ± 0.28 mmol/L vs. 1.18 ± 0.27 mmol/L; P<0.05), and the content of HDL-C were significantly increased (0.73 ± 0.20 mmol/L, 0.78 ± 0.22 mmol/L vs. 0.62 ± 0.14 mmol/L; P<0.05), the T-AOC was significantly increased (10.15 ± 2.76 U/L, 11.29 ± 3.47 U/L vs. 7.95 ± 2.26 U/L; P<0.05), and the activity of GSH-Px was significantly increased(13.79 ± 2.62 U/mg, 14.21 ± 2.87 U/mg vs. 11.90 ± 2.03 U/mg，P<0.05, P<0.01). The histopathological changes of myocardial tissue in SI 160 and 320 mg/kg treated groups were significantly improved. Conclusions SI could effectively lower the plasma glucose level and the blood lipid, improve antioxidant ability, improve antioxidant ability, reduce the damage of free radical, and inhibit the histopathological changes, which suggesting that SI had protective effects on diabetic rats. Key words: Soybean isoflavone; Diabetes; Regulating plasma lipid; Antioxidant

Soybean isoflavone treatment induces osteoblast differentiation and proliferation by regulating analysis of Wnt/β-catenin pathway

It has been reported that soybean isoflavones (SI) have anti-bone resorptive activity in vivo. However, little is known about the cellular and molecular mechanisms of this effect. In this study, we investigated the effects of SI on osteoblast differentiation and proliferation. Results showed that SI promoted osteoblast proliferation and differentiation which could be marked as the formation of hydroxyapatite crystals or extracellular matrix and increased ALP level. SI treatment markedly decreased RANKL levels and increased OPG levels in osteoblast cells. SI resulted in activation of the Wnt/β-catenin pathway. These results demonstrate that SI may be a useful remedy for the treatment of osteoporosis.

Phytophthora sojae and soybean isoflavones, a model to study zoospore chemotaxis

The ability of sensing the signals from hosts, aggregating, and searching for proper sites of invasion is crucial for many soil-borne plant pathogens. One of these is Phytophthora sojae that specifically infects soybean and causes severe yield loss. In the field P. sojae zoospores attracted to soybean exudates isoflavones is an essential step for early infection. Recent studies based on genome mining and gene silencing technologies have shown that this special zoospore behavior relies on G-protein mediated signaling pathways. This review is to summarize researches on P. sojae functional genomics related to G-protein signaling and briefly describe the molecular mechanism of P. sojae zoospore chemotaxis to root exudates, especially isoflavones.

Enhanced Estrogenic Activity of Soybean Isoflavones by Coadministration of Liuwei Dihuang Pills in Ovariectomized Rats.

Soybean isoflavones are beneficial for treating hormone-related diseases. Simultaneous consumption of soybean isoflavones and Liuwei Dihuang pills (LWPs) is effective for treating perimenopausal period syndrome. However, why the combination of isoflavones and LWPs is more effective than ingestion of each component alone remains unknown. Here, we show that enhanced estrogenic activities would appear when the ovariectomized rats were fed with a soybean diet in combination of LWPs treatment. Our further studies explored enhancements of Lactobacillus (19-fold) and Bifidobacterium (12-fold) contents in the intestine of rat and 1.84-fold higher intestinal β-glucosidase activity in LWPs treatment group compared with the control group. As a result, steady-state concentrations of genistein (1.20-fold), daidzein (1.36-fold), and equol (1.43-fold) in serum were significantly elevated in the combination group compared with the soybean alone group. The results present the first evidence of the mechanism of enhanced estrogenic activity of dietary soybean isoflavones in combination with LWPs. Our study indicates that alterations of gut bacteria after LWPs treatment play a key role in the enhanced estrogenic effect of dietary soybean, suggesting a direct relationship between dietary soybean, LWPs, and gut flora.

Preparation and characterisation of soya milk enriched with isoflavone aglycone fermented by lactic acid bacteria combined with hydrothermal cooking pretreatment

SummaryA fermented soya milk (FSM) enriched with isoflavone aglycone (FSM‐SPIA) was prepared from heated soya protein isolate (SPI)‐isoflavone complex. After 48 h of fermentation, FSM‐SPIA contained higher contents of living bacteria, free amino acids and aglycone compared with the FSM of SPI (FSM‐SPI) and the FSM of SPI‐isoflavone complex (FSM‐Mix). In the in‐vitro digestion experiment, FSM‐SPIA showed higher antioxidant capacity and isoflavones (ISO) bioavailability than FSM‐SPI and FSM‐Mix. This was likely due to the soya milk containing a higher level of amino acid, peptides and the presence of soya bean isoflavone. The improved protein digestibility, the interaction and binding ability between proteins and ISO may affect the properties of the protein and the fermented products. The FSM enriched with isoflavone aglycone can be used as a functional fermented drink, as well as an auxiliary food for menopausal women during a specific pathological period.

Enhancement of β-secretase inhibition and antioxidant activities of tempeh, a fermented soybean cake through enrichment of bioactive aglycones

Context: Soybean and its fermented products are the most common source of isoflavones in human food.Objective: The present study quantifies the major glycosides and aglycones in soybean and its fermented product tempeh isoflavone extracts. The comparision of antioxidant effects and BACE1 inhibitory activity between the isoflavones of soybean and tempeh were also established.Materials and methods: The major isoflavones such as daidzein and genistein (aglycones), and their sugar conjugates (glycosides) daidzin and genistin in soybean and tempeh isoflavones were quantified using HPLC analysis. Comparative studies on BACE 1 (β-site amyloid precursor protein cleaving enzyme 1 or β-secretase 1) inhibition and free-radical scavenging activities (diphenyl-1-picrylhydrazyl (DPPH) and ferrous ion chelating ability) were conducted.Results: The amount of actives (mg/100 g) in soybean isoflavone compared with tempeh isoflavone is as follows: daidzein 16.72 mg/100 g versus 38.91 mg/100 g, genistein 11.10 mg/100 g versus 24.03 mg/100 g, daidzin 6.16 mg/100 g versus 0.69 mg/100 g, and genistin 24.61 mg/100 g versus 6.57 mg/100 g. The IC50 values of soybean and tempeh isoflavones against BACE1 were 10.87 and 5.47 mg/ml, respectively. The tempeh isoflavone had a more potent DPPH free-radical scavenging activity (IC50 = 2.67 mg/ml) than the soybean isoflavone (IC50 = 10 mg/ml). The ferrous ion chelating ability of the isoflavones was practically similar (IC50 = 10.40 mg/ml, soybean and 11.13 mg/ml, tempeh).Discussion and conclusion: The present study indicates that tempeh is a healthy supplement to alleviate oxidative stress through the enrichment of aglycones.