Stability of Bisphenol A (BPA) in Oil-In Water Emulsions under Riboflavin Photosensitization

Effects of riboflavin photosensitization on the degradation of bisphenol A (BPA) were determined in oil-in-water (O/W) emulsions containing ethylenediaminetetraacetic acid (EDTA) or sodium azide, which are a metal chelator or a singlet oxygen quencher, respectively. Also, the distribution of BPA between the continuous and dispersed phases in O/W emulsions was analyzed by high-performance liquid chromatography (HPLC). The concentration of BPA in O/W emulsions significantly decreased by 38.6% after 2 h under visible light irradiation and in the presence of riboflavin (P < 0.05). Addition of EDTA and sodium azide protected the decomposition of BPA significantly in a concentration dependent manner (P < 0.05), which implies both transition metals and singlet oxygen accelerate the photodegradation of BPA in O/W emulsions. Approximately 21.7% of the BPA was distributed in the 2.5% (w/v) dispersed lipid particles and 78.3% was in the continuous aqueous phase of the emulsions. The amount of BPA in aqueous phase decreased faster than the amount of BPA in the lipid phase during riboflavin photosensitization (P < 0.05). Thus, the BPA in the aqueous phase was the major target of riboflavin photodegradation in O/W emulsions. Practical Application: Concentration of BPA, an endocrine disrupting chemical, was decreased significantly in oil-in-water emulsions under riboflavin and visible light irradiation. BPA in continuous aqueous phase was major target of riboflavin photosensitization. However, BPA was distributed more densely in lipid phase and more protected from riboflavin photosensitized O/W emulsions. This study can help to decrease the level of BPA in foods made of O/W emulsions containing riboflavin, which could be displayed under visible light irradiation.     

Stability of isoflavone daidzein and genistein in riboflavin, chlorophyll b, or methylene blue photosensitization

ABSTRACT:  Effects of photosensitizers including riboflavin, chlorophyll b , or methylene blue on the stability of daidzein and genistein were studied in model systems by high-performance liquid chromatography (HPLC). Concentration of daidzein and genistein in 80% methanol with riboflavin under light for 7 h was significantly decreased with the apparent 1st-order rate constants of 0.234 and 0.193/h, respectively, ( P < 0.05), while those without riboflavin under light did not change significantly ( P > 0.05). The stability of isoflavone aglycones in the dark did not change significantly irrespective of the presence of riboflavin ( P > 0.05). The concentrations of daidzein and genistein in chlorophyll b or methylene blue model systems under light were not significantly different from those in the dark for 7 h ( P > 0.05). Addition of sodium azide increased the stability of daidzein and genistein in riboflavin photosensitization with concentration dependent manner. However, the protective effects of β-carotene addition on the photodegradation of isoflavones were not high. The stability difference of daidzein and genistein in riboflavin photosensitization may be due to the high reactivity of riboflavin through type I pathway, although singlet oxygen may be involved in part.     

Riboflavin photo-transformation of genistein and changes in radical scavenging activities of photo-transformed genistein derivatives

Genistein was treated with riboflavin photosensitization and the radical scavenging activities of mixtures of genistein and riboflavin were determined using DPPH and ABTS assays. For a period of light irradiation of 100 min, the initial concentration of genistein decreased by 79.1% for riboflavin photosensitization. New peaks were formed and the peak areas increased for a mixture of riboflavin photosensitized genistein. Genistein derivatives were tentatively identified as trihydroxy isoflavones or genisteins with an additional hydroxyl groups. The radical scavenging abilities of photo-sensitized genistein derivatives were significantly (p<0.05) increased, based on DPPH and ABTS results, compared to samples without visible light irradiation for 100 min of photosensitization. Riboflavin photo-transformation can enhance antioxidant activities in isoflavone aglycones.     

Effects of Riboflavin Photosensitized Oxidation on the Volatile Compounds of Soymilk

ABSTRACT: Soymilks with or without added riboflavin in serum bottles were stored under light or in dark at 20 °C. The headspace oxygen and volatile compounds were determined by gas chromatography. Riboflavin had significant effects on the headspace oxygen depletion and volatile compounds formation in soymilk under light ( P < 0.05). Riboflavin did not have significant effects on the formation of volatile compounds and the depletion of headspace oxygen in dark ( P > 0.05). The volatile compounds increased under light, but not in dark as the added riboflavin increased. Storage temperature at 4 °C or 20 °C did not have significant difference in the effect of riboflavin on the headspace oxygen depletion in soymilk under light. Hexanal, an important beany flavor compound, was identified as the major volatile compound in the riboflavin photosensitized soymilk. Singlet oxygen oxidation was involved in the formation of volatile compounds in soymilk under light. Hexanal could be formed by singlet oxygen oxidation. Ascorbic acid, a quencher for singlet oxygen and the excited triplet sensitizer, significantly inhibited the formation of hexanal and total volatiles in soymilk under light.     

Kinetics for Singlet Oxygen Formation by Riboflavin Photosensitization and the Reaction between Riboflavin and Singlet Oxygen

ABSTRACT: The formation of singlet oxygen by riboflavin and the kinetics and mechanisms of riboflavin degradation in aqueous solution under light were determined. The singlet oxygen formation rate by riboflavin was 2.31 μmole oxygen/mL headspace/h of serum bottle. The degradations of riboflavin were 66% in D₂O and 40% in H₂O, respectively, under light after 24 h. The results indicate that singlet oxygen is involved in riboflavin destruction under light. The riboflavin destructions were 94.0% and 15.7% with 0 mM or 160 mM ascorbic acid, respectively, under light after 96 h. The reaction rate between riboflavin and singlet oxygen was 1.01 × 10¹⁰/M/s, which is a diffusion-controlled reaction rate. This explains the extremely fast degradation of riboflavin in foods under light. Ascorbic acid and sodium azide reduce the degradation of riboflavin under light with different quenching mechanisms. Ascorbic acid quenched both singlet oxygen and excited triplet riboflavin. Sodium azide quenched only the singlet oxygen in riboflavin solution with a quenching rate of 1.547 × 10⁷/M/s. With the involvement of both the Type-I and Type-II mechanisms in the riboflavin degradation under light, singlet oxygen quencher alone could not protect the riboflavin from degradation completely. Addition of ascorbic acid can protect riboflavin oxidation in foods exposed to light.     

Escherichia coli biotransformation of daidzein fermentation products from soy‐based foods—relevance to food oestrogenicity‐based functionality

Oestrogenic isoflavones (e.g. daidzein) present in soy‐based foods are likely to be important in food functionality. Biotransformation of daidzein during fermentation‐based soy‐containing food manufacture forms three trihydroxy metabolites, 6‐ortho‐hydroxydaidzein (6‐OHD), 8‐ortho‐hydroxydaidzein (8‐OHD) and 3′‐ortho‐hydroxydaidzein (3′‐OHD) which alters the oestrogenicity of the final food product. We report that Escherichia coli (a key component of the gut microbiome) metabolism converts 8‐OHD to 6‐OHD with a likely concomitant increase in oestrogenicity. This means that the functionality of 8‐OHD‐containing soy‐based foods is altered by gut microbiome metabolism. This change in oestrogenicity‐based food functionality might have benefits for postmenopausal women, while being a feminising health risk for males and could add to the risk of oestrogen‐mediated precocious puberty in girls.     

Formation of Succinyl Genistin and Succinyl Daidzin by Bacillus Species

ABSTRACT:  6"- O -Succinyl-4'-hydroxyisoflavone-7- O -β-D-glucopyranoside (succinyl-β-daidzin) and 6"- O -succinyl-6,4'-dihydroxyisoflavone-7- O -β-D-glucopyranoside (succinyl-β-genistin), 2 new isoflavone metabolites, are found in  cheonggukjang  or  natto , traditional soy-based foods fermented with  Bacillus  species. Standard isoflavones including daidzin, genistin, daidzein, and genistein, and mixtures of isoflavones extracted from roasted soybeans were added to the medium growing  Bacillus subtilis  or  B. subtilis  natto and formation of succinyl-β-daidzin and succinyl-β-genistin were monitored by high-performance liquid chromatography (HPLC). Samples containing  Bacillus  with daidzin and genistin produced succinyl-β-daidzin and succinyl-β-genistin, respectively, while those with daidzein and genistein did not produce succinyl derivatives. Daidzin in samples with  B. subtilis  and  B. subtilis  natto decreased by 39.7% and 10.7%, respectively, for 4 h incubation while genistin decreased by 66.8% and 17.6%, respectively. Genistein decreased faster than daidzein during incubation with  B. subtilis  or  B. subtilis  natto without formation of succinyl derivatives. In the case of mixture of isoflavones, succinyl derivatives increased and β-glucosides and aglycones of isoflavones decreased significantly for 8 h incubation ( P  < 0.05).     

Modification of isoflavone profiles in a fermented soy food with almond powder

Isoflavone profiles of a fermented soy food, cheonggukjang, were modified using almond powder. Isoflavones were analyzed by high performance liquid chromatography (HPLC) with an ultraviolet detector. Malonyl derivatives of isoflavones decreased and aglycones of isoflavones increased in samples with almond powder for 48 h. As added, almond powder increased from 0%, 5%, and 10% (w/w), amounts of aglycones increased to 21.11%, 26.63%, and 32.45% for 48 h, respectively. β-Glucosidase activity in 5% and 10% almond added samples was significantly higher than samples without addition of almond (P < 0.05). The content of succinyl daidzin and succinyl genistin, new metabolites from isoflavones, in almond-added cheonggukjang was significantly lower than control samples, implying that β-glucosidase activity from almond affected negatively the formation of succinyl derivatives (P < 0.05). Principal component analysis (PCA) for isoflavone distribution showed that first principal component (PC1) and second principal component (PC2) expressed 64.78% and 22.26% of the data variability, respectively. Biotransformation of isoflavones in any fermented soy foods can be achieved using natural products containing high β-glucosidase activity such as almond. PRACTICAL APPLICATION: The results of this study can help to modify the structural transformation of phytochemicals in any fermented soy foods using natural products. Adjusting the content of almond powder can achieve wanted profiles, for example, high aglycones content. Also, content of metabolites such as succinyl derivatives can be controlled using proper amounts of almond and fermentation time.     

Characterization of the Nonvolatile Minor Constituents Responsible for the Objectionable Taste of Defatted Soybean Flour

A scheme was developed for the separation of the nonvolatile minor constituents from soy flour which are responsible for the astringent an bitter tastes. The scheme involved solvent extraction, freeze drying, and fractional crystallization. Two fractions, collected by semipreparative HPLC, had the characteristic bitter and astringent tastes. Further fractionation by reverse phase HPLC produced three pure compounds which were identified by UV, NMR spectrometry and elemental analysis, as daidzein, glycitein 7-β-O glucoside, and genestin. Preliminary sensory evaluation showed that these isoflavones might contribute additively to the undesirable bitter and astringent tastes of soy protein products.     

Soy extract has different effects compared with the isolated isoflavones on the proteome of homocysteine-stressed endothelial cells

Epidemiological studies suggest that soy consumption may provide a protection in the development and progression of atherosclerosis. It is under debate, however, whether the soy isoflavones or other compounds are the "active principle". As apoptosis is a driving force in the process of atherosclerosis, we tested whether a soy extract or a combination of the two predominant isoflavones genistein and daidzein, in concentrations as found in the extract, exert similar or different effects on apoptosis in EA.hy 926 endothelial cells after exposure to the endothelial stressor homocysteine. Plasma membrane disintegration and nuclear fragmentation served as relevant apoptosis markers. To assess whether the extract and the genistein/daidzein mixture differently affect cellular target proteins changed in amount by homocysteine treatment, proteome analysis was performed by two-dimensional gel-electrophoresis and peptide mass fingerprinting of regulated protein spots. Homocysteine induced apoptosis in the cells, and both extract and genistein/daidzein inhibited apoptosis to a comparable extent. Whereas the extract prevented for 10 proteins the changes in expression levels as caused by homocysteine, the genistein/daidzein mixture reversed the homocysteine effects on the proteome for 13 proteins. The cytoskeletal protein matrin 3 and a U5 snRNP-specific 40-kDa protein were the only protein entities where both extract and genistein/daidzein reversed the homocysteine-induced changes in a common way. In conclusion, our studies provide evidence that an isoflavone containing soy extract and isolated isoflavones, despite similar effects on inhibition of homocysteine-induced apoptosis in endothelial cells, affect a quite different spectrum of cellular target proteins.     

HPLC with coulometric electrode array detection Determination of daidzein and genistein in soy based infant food, soy milk and soy based supplements

A HPLC method coupled with coulometric electrode array detection for determination of daidzein and genistein in soy milk, soy-based infant food and nutritional supplements is described. The samples were spiked with bisphenol A (internal standard), extracted and hydrolyzed in an acid ethanolic solution. After purification of the extract on a C-18 cartridge the compounds were separated on a C-18 reversed phase column (50?mM sodium acetate adapted to pH?4.8 with glacial acetic acid/methanol at 450/550, v/v). The compounds were detected at eight electrodes set on potentials between +390?mV and +810?mV (in increments of 60?mV) against modified palladium electrodes. The contents of daidzein and genistein were determined in several commercial samples.     

Intermolecular interactions in phytochemical model systems studied by NMR diffusion measurements

Novel functional foods, such as tomato juice with soy, represent a new strategy to increase consumption of health promoting ingredients and phytochemicals. Interactions between soy protein, isoflavones, and tomato carotenoids could impact the bioaccessibility and bioavailability of individual phytochemicals. The primary objective of this study was to assess possible interactions between daidzein and daidzin, soy protein and carotenoids using proton one-dimensional and two-dimensional pulsed field gradient nuclear magnetic resonance spectroscopy experiments.     

Combination of low dose of genistein and daidzein has synergistic preventive effects on isogenic human prostate cancer cells when compared with individual soy isoflavone

The reduced incidence of prostate cancer (PCa) in Asia countries has been attributed to high soy diets, and major soy isoflavones, in particular daidzein and genistein, are thought to be the source of the beneficial and anti-cancer effects of soy foods. However, attention has been drawn to the safety of using high levels of soy isoflavones in humans, which is especially the concern for consumers taking regular soy isoflavone dietary supplements. The main objective of this study is thus to identify a soy isoflavone combination with lower levels of daidzein and genistein to be a more efficacious and safer chemo-preventive agent for PCa. The anticancer effects of daidzein and genistein, and their combinations on early-stage androgen-dependent PCa cells (LNCaP) and bone metastatic LNCaP-derivative PCa cells (C4-2B) were compared. Cells were treated with varying concentrations of daidzein, genistein (25–200 μM) or their combinations (25 or 50 μM) and cell proliferation, apoptosis, cell cycles and cellular uptakes of the isoflavones were measured after 48 h. Daidzein and genistein showed a synergistic effect on inhibiting cell proliferation and inducing apoptosis of both PCa cells. Twenty-five μM daidzein/50 μM genistein and 50 μM daidzein/50 μM genistein significantly increased the apoptotic effects on C4-2B cells although they did not show any effect when used individually. Except 50 μM daidzein/50 μM genistein, all other combinations had no impacts on cell cycles. For treatment with soy isoflavone combination, genistein was always better taken up than daidzein by both LNCaP and C4-2B cells.     

Chemistry and Reaction of Singlet Oxygen in Foods

Singlet oxygen is a highly reactive, electrophilic, and nonradical molecule. It is different from diradical triplet oxygen in its electron arrangement. Photosensitizers can form singlet oxygen from triplet oxygen in the presence of light. The reaction rate of singlet oxygen with foods is much greater than that of triplet oxygen due to the low activation energy. Singlet oxygen oxidation produces undesirable compounds in foods during processing and storage. However, carotenoids and tocopherols in foods can minimize singlet oxygen oxidation. The in‐depth scientific knowledge on the formation, reactions, quenching mechanisms, and kinetics of singlet oxygen can greatly improve the quality of foods by minimizing the oxidation during processing and storage. The single oxygen oxidation of foods has contributed to the explanation of several important chemical reactions in the reversion flavor in soybean oil, sunlight flavor in milk products, and the rapid losses of vitamin D, riboflavin, and ascorbic acid in milk under light storage.     

Effects of Riboflavin Photosensitization on the Degradation of Bisphenol A (BPA) in Model and Real-Food Systems

ABSTRACT:  Effects of riboflavin photosensitizations on the stability of bisphenol A (BPA), a well-known endocrine disrupting chemical, were studied in model and real-food systems by high-performance liquid chromatography (HPLC). Concentration of BPA was significantly decreased under light exposure ( P < 0.05) as the concentration of riboflavin increased while those without riboflavin under light or those with riboflavin in the dark did not change significantly ( P > 0.05). Addition of 50, 100, and 200 μM sodium azide significantly increased the stability of BPA in riboflavin photosensitization with concentration dependent manner ( P < 0.05), implying that a singlet oxygen or type II pathway played a role in the photodegradation of BPA. Stability of BPA in riboflavin was significantly increased in the presence of high concentration of tert -butanol, a hydroxyl radical quencher, under light storage for 80 min, indicating hydroxyl radicals were involved and contributed to the degradation of BPA, at least in part. Availability of riboflavin photosensitization on the photodegradation of BPA was tested in 2 canned tea beverages with different phenolic contents. BPA was more stable in the beverage sample with higher total phenolic contents and free radical scavenging ability. The photodegradation of BPA in riboflavin photosensitization can be an efficient way to decrease the concentration of BPA from environmental or food systems.     

不同波段的光照对无菌牛奶中光敏剂降解的影响

在油脂光照氧化过程中起催化作用的光敏剂在不同可见光照波段下有着不同的吸收特性。光敏剂对光照的吸收量越大,光敏剂降解得越迅速。研究不同可见光光照波段对无菌牛奶中光敏剂核黄素与原卟啉降解的影响,确定出这两种光敏剂降解最为迅速的光照波段。实验结果表明核黄素在400~500nm、原卟啉在500~600nm光照波段下降解迅速。因此,牛奶在这两个光照波段下氧化变质可能更为迅速。     

Antioxidant capacities of α-tocopherol,trolox, ascorbic acid,and ascorbyl palmitate in riboflavin photosensitized oil-in-water emulsions

Antioxidant capacities of α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate at 0.01, 0.1, and 1.0 mM in riboflavin photosensitized oil-in-water (O/W) emulsions were determined using headspace oxygen depletion, lipid hydroperoxide, and headspace volatile analyses. After 32 h visible light irradiation, headspace oxygen in O/W emulsions without adding antioxidants, with 1.0 mM α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate decreased to 18.50%, 18.85%, 16.01%, 17.92%, and 19.88%, respectively, whereas those samples in the dark were 20.74%. Trolox and ascorbic acid acted as prooxidants while their lipophilic counterparts, α-tocopherol and ascorbyl palmitate, respectively showed antioxidant properties. Similar antioxidative or prooxidative properties of the tested compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. However, the prooxidant and antioxidant properties of the tested compounds were not clearly shown at 0.01 and 0.1 mM concentration. Both the type and concentration of antioxidants influenced the antioxidant capacities in riboflavin photosensitized O/W emulsions.     

Light-Induced Changes in Taste,Appearance, Odor,and Riboflavin Content of Cheese

Light-induced changes in taste, appearance, odor, and riboflavin content of common cheeses stored under controlled laboratory conditions and in the dairy cases of four local grocery stores were investigated. Sensory evaluation was performed by 25 untrained panelists, and the riboflavin content was determined by HPLC method. The data obtained from controlled storage indicated that light intensity, type of packaging paper, and piece thickness affected riboflavin retention and color in stored cheese. However, under the display conditions used in the four local stores, retail cheese retained its riboflavin after a display time of 14 d with no significant change in taste, appearance, or odor.     

An Assessment of Light-Induced Off-Flavors in Retail Milk

Samples of whole and skim milk from two local dairy plants that were packaged in 3.8-L plastic containers (nonreturnable high density polyethylene) and 1.9, .95, and .48-L fiberboard containers and displayed in the dairy cases of four local grocery stores under normal fluorescent light were analyzed for light-induced changes in flavor and riboflavin content. Milk samples were analyzed daily for flavor, odor, appearance, and riboflavin content. Sensory evaluation was by 25 untrained panelists, and riboflavin was determined by HPLC method. Milk samples were analyzed first in summer, then repeated in winter. Data indicated that under typical production and storage conditions in the area, type and size of container, fat content, and season of production had no major damaging effects on flavor, odor, appearance, or riboflavin content of retail milk.     

Effects of riboflavin photosensitization on the changes of isoflavones in soymilk

Effects of riboflavin photosensitization on the distribution of isoflavones in commercially available soymilk were analyzed using high-performance liquid chromatography (HPLC). Total isoflavones (TI) in soymilk with riboflavin (1000 ppm, w/v) under light were significantly different from those stored in the dark for 24 h (P < 0.05), while TI in samples with 0 and 1000 ppm added riboflavin were not significant from each other in dark conditions (P > 0.05). To test the effects of the concentration of riboflavin on TI, soymilk was mixed with riboflavin to make 0, 100, 250, and 500 ppm (w/v) and stored under light at 25 degrees C for 24 h. TI in soymilk with 100 ppm riboflavin under light significantly decreased by 13.5% for 24 h (P < 0.05) compared to control samples and were not significantly different from those with 250 or 500 ppm samples (P > 0.05). Daidzin and genistin were predominant isoflavones in soymilk, and the rate of photo degradation of genistin was higher than that of daidzin for 24 h in soymilk under riboflavin photosensitization.