The conversion and deglycosylation of isoflavones and anthocyanins in black soymilk process

Novel strategy to raise the content of aglycone isoflavones in soymilk and gel: Effect of germination on the physicochemical properties

Germination holds the key to nutritional equilibrium in plant grains. In this study, the effect of soybean germination on the processing of soymilk (SM) and glucono-δ-lactone (GDL) induced soymilk gel (SG) was investigated. Germination promoted soybean sprout (SS) growth by activating the energy metabolism system. The energy metabolism was high during the three-day germination and was the most vigorous on the second day of germination. After germination, protein dissolution was improved in SM, and endogenous enzymes produced small molecule proteins. Small molecule proteins were more likely to aggregate to produce SM protein particles. Germination increased the water-holding capacity of SG induced by GDL but weakened the strength. Furthermore, the dynamic fluctuations in isoflavone content were closely monitored throughout the processing of soybean products, including SS, SM, and SG. Although the total amount of isoflavones in SM and SG processed from germinated soybeans decreased, a significant enrichment in the content of aglycone isoflavones was observed. The content of aglycone isoflavones in SG processed from germinated soybeans on the second day of germination was 736.17 ± 28.49 µg/g DW, which was 83.19 % higher than that of the control group. This study demonstrates that germination can enhance the nutritional value of soybean products, providing innovative opportunities for the development of health-promoting soybean-based products.

Enzymatic synthesis of Vaccinium blue using vaccinoside as a bifunctional precursor

Since Tang dynasty in China, the fresh leaves of Vaccinium bracteatum (VBL) have been applied as natural pigment to produce black rice. However, detailed information on its biosynthetic mechanism still remained unclear. Following rice dyeing capacity assay, vaccinoside, one of iridoid glycosides, was identified as the key active compound. Increased methodical research demonstrated vaccinoside as a distinct bifunctional precursor, which could be catalyzed by polyphenol oxidase or β-glucosidase independently, followed by reaction with 15 amino acids to give blue pigments (VBPs; λmax 581-590 nm) of different hues. Two synthetic pathways of VBPs were proposed, using multiple techniques such as HPLC, HPSEC, UV-Vis spectrum and colorimeter as analysis tools. Black rice was interpreted to be prepared by cooking, using vaccinoside, intrinsic enzymes from fresh VBL and rice protein in combination. These findings promote the understanding of VBP formation mechanisms and provide an efficient method of producing novel Vaccinium blue pigments.

Overexpression of R2R3-MYB IbMYB1a induces anthocyanin pigmentation in soybean cotyledon

KEY MESSAGE

This is the first report showing anthocyanin accumulation in the soybean cotyledon via genetic transformation of a single gene. Soybean [Glycine max (L.) Merrill] contains valuable components, including anthocyanins. To enhance anthocyanin production in Korean soybean Kwangankong, we utilized the R2R3-type MYB gene (IbMYB1a), known for inducing anthocyanin pigmentation in Arabidopsis. This gene was incorporated into constructs using two promoters: the CaMV 35S promoter (P35S) and the β-conglycinin promoter (Pβ-con). Kwangankong was transformed using Agrobacterium, and the presence of IbMYB1a and Bar transgenes in T0 plants was confirmed through polymerase chain reaction (PCR), followed by gene expression validation. Visual inspection revealed that one P35S:IbMYB1a and three Pβ-con:IbMYB1a lines displayed seed color change. Pβ-con:IbMYB1a T1 seeds accumulated anthocyanins in cotyledon outer layers, whereas P35S:IbMYB1a and non-transgenic black soybean (Cheongja 5 and Seum) accumulated anthocyanins in the seed coat. During the germination and growth phase, T1 seedlings from Pβ-con:IbMYB1a lines exhibited anthocyanin pigmentation in cotyledons for up to 1 month without growth aberrations. High-performance liquid chromatography confirmed cyanidin-3-O-glucoside as the major anthocyanin in the Pβ-con:IbMYB1a line (#3). We analyzed the expression patterns of anthocyanin biosynthesis genes, chalcone synthase 7,8, chalcone isomerase 1A, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, dihydroflavanol reductase 1, dihydroflavanol reductase 2, anthocyanidin synthase 2, anthocyanidin synthase 3, and UDP glucose flavonoid 3-O-glucosyltransferase in transgenic and control Kwangankong and black soybean (Cheongja 5 and Seum) seeds using quantitative real-time PCR. We conclude that the induction of gene expression in transgenic plants in comparison with Kwangankong was attributable to IbMYB1a transformation. Notably, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, and dihydroflavanol reductase 1 were abundantly expressed in black soybean seed coat, distinguishing them from transgenic cotyledons.

Gut microbial metabolites of dietary polyphenols and their potential role in human health and diseases

Polyphenols contribute as one of the largest groups of compounds among all the phytochemicals. Common sources of dietary polyphenols are vegetables, fruits, berries, cereals, whole grains, etc. Owing to their original form, they are difficult to get absorbed. Dietary polyphenols after undergoing gut microbial metabolism form bioaccessible and effective metabolites. Polyphenols and derived metabolites are all together a diversified group of compounds exhibiting pharmacological activities against cardiovascular, cancer, oxidative stress, inflammatory, and bacterial diseases. The formed metabolites are sometimes even more bioavailable and efficacious than the parent polyphenols. Studies on gut microbial metabolism of dietary polyphenols have introduced new approach for the use of polyphenol-rich food in the form of supplementary diet. This review provides insights on various aspects including classification of polyphenols, gut microbiota-mediated metabolism of polyphenols, chemistry of polyphenol metabolism, and pharmacological actions of gut microbial metabolites of polyphenols. It also suggests the use of polyphenols from marine source for the microbial metabolism studies. Till date, gut microbial metabolism of polyphenols from terrestrial sources is extensively studied as compared to marine polyphenols. Marine ecosystem is a profound but partially explored source of phytoconstituents. Among them, edible seaweeds contain high concentration of polyphenols, especially phlorotannins. Hence, microbial metabolism studies of seaweeds can unravel the pharmacological potential of marine polyphenol-derived metabolites.

Effect of ultrasound and microwave treatment on the level of volatile compounds, total polyphenols, total flavonoids, and isoflavones in soymilk processed with black soybean (Glycine max (L.) Merr.)

This study analyzed the effect of ultrasound treatment (up to 9 min, 20 kHz, 130 W) on the volatile compounds, total polyphenols, total flavonoids, and isoflavones (daidzein, genistein, daidzin, genistin, and glycitin) in soymilk processed with microwave-roasted (700 W for 270 s) black soybean (Glycine max (L.) Merr.). 1-Hexanol and 1-octen-3-ol, unpleasant soybean flavors, were found to decrease by up to 96.13% and 93.04%, respectively, in ultrasound-treated soymilk compared to the control. 2,3-Diethyl-5-methylpyrazine, a baked flavor, which exhibited the highest odor impact ratio in soymilk processed with microwave-roasted soybean, increased significantly during ultrasound treatment (p < 0.05). The content of total isoflavones, polyphenols, and flavonoids increased (p < 0.05) with the increase in ultrasound treatment time. Spearman's correlation analysis showed that browning was positively correlated (p < 0.01) with total phenols, total furans, total pyrazines, total polyphenols, and total isoflavones. This study discusses the applicability of microwave-roasted soybeans for improving the volatile profile and bioactive compounds in soymilk and provides information on the effects of ultrasound treatment on the volatile compounds, total polyphenols, flavonoids, and isoflavones in soymilk.

Effect of Fermented Matrix on the Color and Stability of Strawberry and Blueberry Anthocyanins during the Storage of Fruit Yogurts and Soy-Based and Bean-Based Fruit Yogurt Alternatives

The effect of the fermented matrix on the color and the stability of anthocyanins contained in strawberry (Fragaria ananassa D.) and highbush blueberry (Vaccinium corymbosum L.) preparations for fruit yogurts, as well as soy-based (Glycine max L. Merr.) and bean-based (Phaseolus vulgaris L.) yogurt alternatives, stored for 8 weeks, was evaluated. To produce the fermented bean matrix, germinated seeds of white and black beans were used. The obtained fermented matrices had similar pH levels, while the soy-based and black bean-based yogurt alternatives were characterized by their high content of isoflavone aglycones and phenolic acids. The degradation of anthocyanins in strawberry and blueberry fermented products during storage followed first-order reaction kinetics. Significant differences were found depending on the fermented plant-based matrix. The fermented soy-based matrix demonstrated the highest T1/2 values for total anthocyanins (26.3 and 88.8 weeks for strawberry and blueberry products, respectively), whereas the yogurts exhibited the lowest values (13.3 and 49.3 weeks for strawberry and blueberry products, respectively). In the comparison of anthocyanin degradation during the storage of bean-based products, the pigments in the matrix obtained from fermented black beans showed better stability. During storage, the loss of anthocyanins was higher in strawberry products than in blueberry products, particularly with respect to malvidin and petunidin derivatives and acylated anthocyanins, which exhibited high stability. The total color difference (ΔE*) of blueberry plant-based products after an 8 week storage period ranged from 1.1 to 1.5. This data suggests that the addition of a coloring ingredient for industrial production may not be required.

The Interaction between Flavonoids and Intestinal Microbes: A Review

In recent years, research on the interaction between flavonoids and intestinal microbes have prompted a rash of food science, nutriology and biomedicine, complying with future research trends. The gut microbiota plays an essential role in the maintenance of intestinal homeostasis and human health, but once the intestinal flora dysregulation occurs, it may contribute to various diseases. Flavonoids have shown a variety of physiological activities, and are metabolized or biotransformed by gut microbiota, thereby producing new metabolites that promote human health by modulating the composition and structure of intestinal flora. Herein, this review demonstrates the key notion of flavonoids as well as intestinal microbiota and dysbiosis, aiming to provide a comprehensive understanding about how flavonoids regulate the diseases by gut microbiota. Emphasis is placed on the microbiota-flavonoid bidirectional interaction that affects the metabolic fate of flavonoids and their metabolites, thereby influencing their metabolic mechanism, biotransformation, bioavailability and bioactivity. Potentially by focusing on the abundance and diversity of gut microbiota as well as their metabolites such as bile acids, we discuss the influence mechanism of flavonoids on intestinal microbiota by protecting the intestinal barrier function and immune system. Additionally, the microbiota-flavonoid bidirectional interaction plays a crucial role in regulating various diseases. We explain the underlying regulation mechanism of several typical diseases including gastrointestinal diseases, obesity, diabetes and cancer, aiming to provide a theoretical basis and guideline for the promotion of gastrointestinal health as well as the treatment of diseases.

Metabolomic Analysis Reveals Changes of Bioactive Compounds in Mung Beans (Vigna radiata) during γ-Aminobutyric Acid Enrichment Treatment

Soaking together with Heat and Relative Humidity (HRH) treatment has been applied successfully to enrich γ-aminobutyric acid (GABA) in mung beans. However, whether and how the above GABA enrichment processing influences the other bioactive molecules is elusive. In the present study, mung beans were soaked and then treated by HRH for 5 or 7 h. By using metabolomics techniques, the changes of 496 metabolites were determined. The relative content of flavonoids and phenolic acids increased during soaking but slightly decreased during HRH. Intriguingly, soaking and HRH had the opposite effects on the glycosylation of polyphenols. The relative content of glycosylated or un-glycosylated polyphenols increased during soaking or HRH, respectively. The relative content of α-ketoglutaric acid increased more than 20 times after 5 h HRH treatment. Bioactive molecules could be enriched during GABA enrichment processing. Depending on the desired bioactive compounds, soaking and different duration of HRH treatment could be selected.

Effect of Soybean Protein Isolate-7s on Delphinidin-3-O-Glucoside from Purple Corn Stability and Their Interactional Characterization

Anthocyanins are abundant in purple corn and beneficial to human health. Soybean protein isolate-7s (SPI-7s) could enhance the stability of anthocyanins. The stable system of soybean protein isolate-7s and delphinidin-3-O-glucoside complex (SPI-7s-D3G) was optimized using the Box–Behnken design at pH 2.8 and pH 6.8. Under the condition of pH 2.8, SPI-7s effectively improved the sunlight-thermal stabilities of delphinidin-3-O-glucoside (D3G). The thermal degradation of D3G conformed to the first order kinetics within 100 min, the negative enthalpy value and positive entropy value indicated that interaction was caused by electrostatic interaction, and the negative Gibbs free energy value reflected a spontaneous interaction between SPI-7s and D3G. The interaction of SPI-7s-D3G was evaluated by ultraviolet visible spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy. The results showed that the maximum absorption peak was redshifted with increasing the α-helix content and decreasing the β-sheet contents, and D3G quenched the intrinsic fluorescence of SPI-7s by static quenching. There was one binding site in the SPI-7s and D3G stable system. The secondary structure of SPI-7s had changed and the complex was more stable. The stabilized SPI-7s-D3G will have broad application prospects in functional foods.

Pyruvic acid stress caused color attenuation by interfering with anthocyanins metabolism during alcoholic fermentation

Anthocyanin accounts for wine color performance, while it is susceptive to saccharomyces cerevisiae, causing threatened stability. Considering pyranoanthocyanin performed better color and stability, converting anthocyanins to pyranoanthocyanins in advance during fermentation was an ideal way for color improvement. Thus, pyruvic acid (PA) as the precursor of vitisin A was applied to fermentation with cyanidin-3-O-glucoside (C3G). Results showed that PA-stress leads to a color loss associated with a decrease in C3G and cyanidin. However, the content of pyranoanthocyanins under PA stress is unvaried. LC-MS-based non-target metabolomics revealed that superfluous PA can disturb the process of glycolysis and tricarboxylic acid cycle. Importantly, 1291 molecular features were increased and 1122 were decreased under PA-stress, in which several anthocyanins derivatization and isomerization were changed, contributing to color performance. This study indicated that extra PA is unfriendly to anthocyanins during fermentation, playing an adverse effect on color, which should be avoided in wine production.

Time-Course Comparative Metabolome Analysis of Different Barley Varieties during Malting

Malt production is one of the important uses of barley, and its quality differs greatly depending on the barley varieties used. In this study, ultraperformance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry technology was used to investigate the temporal changes of metabolites during malting in two barley varieties: Franklin (malt barley) and Yerong (non-malt barley). Also, differences in metabolite profiles were compared in the kilned malt between two other malt barley varieties (Copeland and Planet) and two non-malt varieties (ZD10 and Hua30). Results showed that degradation of trisaccharide and accumulation of UDP-glucose and mannose-1-phosphate are the key metabolic events during steeping, with Franklin showing earlier and greater changes. Earlier increase of sugars and amino acids in Franklin is associated with its faster germination rate. Comparative metabolome analysis of kilned malt from the different barley varieties indicated that malt barley accumulated more sugars, hordatine-glucoside, and oxoproline, and non-malt barley accumulated more polyphenols and monogalactosylmonoacylglycerol. These results improved the understanding of the genotypic difference in the formation of malt quality at the metabolomic level.

Impact of processing technologies on isoflavones, phenolic acids, and antioxidant capacities of soymilk prepared from 15 soybean varieties

In the present study, soymilk samples were prepared from 15 soybean varieties by employing dry method-raw slurry filtration (D-BAF), dry method-cooked slurry filtration (D-BBF), wet method-raw slurry filtration (W-BAF), and wet method-cooked slurry filtration (W-BBF). Different varieties of soybean and processing techniques were found to impose a significant impact on total phenolics, total flavonoids, phenolic acids, isoflavones and antioxidant capacity of soymilk samples. Overall, the soymilk prepared by W-BAF exhibited a higher level of total phenolic content and antioxidant activity. The soymilk samples prepared by W-BBF presented higher values for total flavonoid content and ferric-reducing antioxidant power assay. The soymilk prepared by W-BBF presented higher subtotal values of phenolic acids. In comparison, the soymilk prepared by D-BAF exhibited high amount of total isoflavones followed by the soymilk processed by W-BAF. Overall, the wet method was found to be responsible for improved phenolic contents and antioxidant activity of soymilk sample.

Preparation and pH Controlled Release of Fe3O4/Anthocyanin Magnetic Biocomposites

Anthocyanins are a class of antioxidants extracted from plants, with a variety of biochemical and pharmacological properties. However, the wide and effective applications of anthocyanins have been limited by their relatively low stability and bioavailability. In order to expand the application of anthocyanins, Fe3O4/anthocyanin magnetic biocomposite was fabricated for the storage and release of anthocyanin in this work. The magnetic biocomposite of Fe3O4 magnetic nanoparticle-loaded anthocyanin was prepared through physical intermolecular adsorption or covalent cross-linking. Scanning electron microscopy (SEM), Dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and thermal analysis were used to characterize the biocomposite. In addition, the anthocyanin releasing experiments were performed. The optimized condition for the Fe3O4/anthocyanin magnetic biocomposite preparation was determined to be at 60 °C for 20 h in weak alkaline solution. The smooth surface of biocomposite from SEM suggested that anthocyanin was coated on the surface of the Fe3O4 particles successfully. The average size of the Fe3O4/anthocyanin magnetic biocomposite was about 222 nm. Under acidic conditions, the magnetic biocomposite solids could be repeatable released anthocyanin, with the same chemical structure as the anthocyanin before compounding. Therefore, anthocyanin can be effectively adsorbed and released by this magnetic biocomposite. Overall, this work shows that Fe3O4/anthocyanin magnetic biocomposite has great potential for future applications as a drug storage and delivery nanoplatform that is adaptable to medical, food and sensing.

Hydrothermal deglycosylation and deconstruction effect of steam explosion: Application to high-valued glycyrrhizic acid derivatives from liquorice

In this work, steam explosion (SE) was exploited as a green and facile process to deconstruct liquorice's structure and deglycosylate glycyrrhizic acid (GL) to improve conversion and diffusion efficacy of GL and its hydrolyzed products. Results showed SE induced auto-hydrolysis of GL into glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) and glycyrrhetinic acid (GA), by which 30.71% of GL conversion, 5.24% and 21.47% of GAMG and GA formation were obtained. GL hydrolytic pathways were revealed by reaction kinetics and thermodynamics, which possessed complex consecutive and parallel reactions with endothermic, non-spontaneous and entropy-decreasing features. SE referred to cause cleavage of the β-1,3 glycosidic bond in GL which was hydrolyzed to GA as a main product and GAMG and glucuronic acids as minor products. Diffusion of hydrolyzed products was accelerated by raising the diffusion coefficient and shortening the equilibrium time by over 90%. This work provides a sustainable and efficient route for product conversion and function enhancement of bioactive components.

Anti-Adipogenic Effects of Delphinidin-3-O-β-Glucoside in 3T3-L1 Preadipocytes and Primary White Adipocytes

Delphinidin-3-O-β-glucoside (D3G) is a health-promoting anthocyanin whose anti-obesity activity has not yet been thoroughly investigated. We examined the effects of D3G on adipogenesis and lipogenesis in 3T3-L1 adipocytes and primary white adipocytes using real-time RT-PCR and immunoblot analysis. D3G significantly inhibited the accumulation of lipids in a dose-dependent manner without displaying cytotoxicity. In the 3T3-L1 adipocytes, D3G downregulated the expression of key adipogenic and lipogenic markers, which are known as peroxisome proliferator-activated receptor gamma (PPARγ), sterol regulatory element-binding transcription factor 1 (SREBP1), CCAAT/enhancer-binding protein alpha (C/EBPα), and fatty acid synthase (FAS). Moreover, the relative protein expression of silent mating type information regulation 2 homolog 1 (SIRT1) and carnitine palmitoyltransferase-1 (CPT-1) were increased, alongside reduced lipid levels and the presence of several small lipid droplets. Furthermore, D3G increased the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), which suggests that D3G may play a role in AMPK and ACC activation in adipocytes. Our data indicate that D3G attenuates adipogenesis and promotes lipid metabolism by activating AMPK-mediated signaling, and, hence, could have a therapeutic role in the management and treatment of obesity.

Sampling for DUS Test of Flower Colors of Ranunculus asiaticus L. in View of Spatial and Temporal Changes of Flower Colorations, Anthocyanin Contents, and Gene Expression Levels

Sampling for DUS test of flower colors should be fixed at the stages and sites that petals are fully colored, and besides, flower colorations are uniform among individuals and stable for a period of time to allow testers to get consistent results. It remains a problem since spatial and temporal flower colorations are reported a lot but their change traits are little discussed. In this study, expression state, uniformity and stability of color phenotypes, anthocyanin contents, and gene expression levels were taken into account based on measurements at 12 development stages and three layers (inner, middle, and outer petals) of two varieties of Ranunculus asiaticus L. to get their best sampling. Our results showed that, outer petals of L9–L10 (stage 9–stage 10 of variety ‘Jiaoyan zhuanhong’) and C5–C6 (stage 5–stage 6 of variety ‘Jiaoyan yanghong’) were the best sampling, respectively. For DUS test, it is suggested to track flower colorations continuously to get the best sampling as well as representative colors since different cultivars had different change traits, and moreover, full expression of color phenotypes came later and lasted for a shorter duration than those of anthocyanin contents and gene expressions. Our innovation exists in following two points. Firstly, a model of change dynamic was introduced to illustrate the change traits of flower colorations, anthocyanin contents, and gene expressions. Secondly, genes used for expression analysis were screened on account of tentative anthocyanins, which were identified based on comparison between liquid chromatography–mass spectrometry (LC–MS) results and molecular mass and mass fragment pattern (M²) of each putative anthocyanin and their fragments deduced in our previous study. Gene screening in this regard may also be interest for other non-model plant genera with little molecular background.

BadGluc, a β-glucosidase from Bjerkandera adusta with anthocyanase properties

A glycosidase of the basidiomycete Bjerkandera adusta (BadGluc) was found in screenings to possess a strong decolorizing ability towards malvidin-3-galactoside, an anthocyanin abundant in various berry fruits. The BadGluc was purified from the culture supernatant via FPLC, and the corresponding gene was identified which showed low similarity to other characterized glucosidases. Scanning the primary sequence with PROSITE no active site motif was detected. Eventually, a specific 18 aa consensus pattern was identified manually. The active site motif possessed an undescribed sequence which was only found in a few hypothetical proteins. The corresponding gene was cloned and expressed in Pichia pastoris GS115 yielding activities up to 100 U/L using 4-nitrophenyl-β-d-glucopyranoside (pNPG) as substrate. The enzyme possessed a good temperature (70% after 1 h at 50°C) and pH stability (70% between pH 2 and 7.5), and preferably catalysed the hydrolysis of delphinidin-3-glucoside and cyanidin-3-glucoside, regardless of the position of the terminal Hexa-His tag. This novel glucosidase worked in aqueous solution as well as on pre-stained fabrics making it the first known candidate anthocyanase for applications in the detergent and food industries.