Bioconversion and bioaccessibility of isoflavones from sogurt during in vitro digestion

Peptidomics-based identification of antihypertensive and antidiabetic peptides from sheep milk fermented using Limosilactobacillus fermentum KGL4 MTCC 25515 with anti-inflammatory activity: in silico, in vitro, and molecular docking studies

This study investigated the synthesis of bioactive peptides from sheep milk through fermentation with Limosilactobacillus fermentum KGL4 MTCC 25515 strain and assessed lipase inhibition, ACE inhibition, α-glucosidase inhibition, and α-amylase inhibition activities during the fermentation process. The study observed the highest activities, reaching 74.82%, 70.02%, 72.19%, and 67.08% (lipase inhibition, ACE inhibition, α-glucosidase inhibition, and α-amylase inhibition) after 48 h at 37°C, respectively. Growth optimization experiments revealed that a 2.5% inoculation rate after 48 h of fermentation time resulted in the highest proteolytic activity at 9.88 mg/mL. Additionally, fractions with less than 3 kDa of molecular weight exhibited superior ACE-inhibition and anti-diabetic activities compared to other fractions. Fermentation of sheep milk with KGL4 led to a significant reduction in the excessive production of NO, TNF-α, IL-6, and IL-1β produced in RAW 267.4 cells upon treatment with LPS. Peptides were purified utilizing SDS-PAGE and electrophoresis on 2D gels, identifying a maximum number of proteins bands ranging 10-70 kDa. Peptide sequences were cross-referenced with AHTPDB and BIOPEP databases, confirming potential antihypertensive and antidiabetic properties. Notably, the peptide (GPFPILV) exhibited the highest HPEPDOCK score against both α-amylase and ACE.

Effects of fermentation with different probiotics on the quality, isoflavone content, and flavor of okara beverages

The present study aimed to prepare and evaluate a new probiotic functional beverage, using single-probiotic and compound probiotic fermentation on okara. Four different forms of fermentation microorganisms used were Lacticaseibacillus rhamnosus S24 (Lr), Lacticaseibacillus paracasei 6244 (Lp), Lactobacillus acidophilus 11,073 (La), and mixed fermentation (Lr + Lp + La). The physicochemical properties, antioxidant activity, flavor change, and storage period of fermented okara beverages with probiotics were investigated. The results showed that different fermentation schemes could significantly improve the physicochemical properties, antioxidant activity, and sensory quality of the okara beverages. The number of viable bacteria in the Lp group (3.53 × 108 CFU/mL), isoflavone content (0.514 μg/mL) were the highest; total phenol and flavonoid content were 3.32 and 5.68 times higher than in the CK group, respectively. DPPH and ABTS+ free radical scavenging rates were increased by 11.32% and 20%, respectively (p < .05). Through SPME/GC-MS analysis, 44 volatile compounds were identified in the Lr + Lp + La groups, mainly as a result of changes in alcohols and aldehydes produced by fermentation metabolism. It enhances the floral and fruity aroma of the okara beverage. All probiotic-fermented okara beverages can be stored at 4°C for 15 days, with probiotic activity greater than 107 CFU/mL. This study can obtain a probiotic okara beverage rich in soybean isoflavones and with good flavor. Overall, okara can be used to develop functional beverages containing probiotics and contribute to a zero-waste approach in the food industry.

Mucin coated protein-polyphenol microcarriers for daidzein delivery

Daidzein, an isoflavone found abundantly in legumes, may benefit from bypassing upper gut absorption to reach the colon where it can be metabolized into the potent estrogen equol by the gut microbiome. To achieve this, we developed mucin coated protein-tannin multilayer microcarriers. Highly porous functionalized calcium carbonate (FCC) microparticles efficiently absorbed daidzein from a dimethyl sulfoxide solution, with a loading capacity of 21.6 ± 1.8 wt% as measured by ultra-high pressure liquid chromatography - mass spectrometry (UPLC-MS). Daidzein-containing FCC microparticles were then coated with a bovine serum albumin (BSA)-tannin n-layer film terminated with mucin ((BSA-TA)n-mucin) by layer-by-layer deposition from corresponding aqueous solutions followed by FCC decomposition with HCl. Raman spectroscopy confirmed mucin-tannin complexation involving both hydrophobic interactions and hydrogen bonding. The resulting multilayer microcarriers contained 54 wt% of nanocrystalline daidzein as confirmed by X-ray diffraction and UPLC-MS. Preliminary screening of several types of mucin coatings using an in vitro INFOGEST digestion model demonstrated that mucin type III from porcine stomach provided the highest protection against upper intestinal digestion. (BSA-TA)8-mucin and (BSA-TA)4-mucin microcarriers retained 71 ± 16.4% and 68 ± 4.6% of daidzein, respectively, at the end of the small intestinal phase. Mucin-free (BSA-TA)8 retained a lower daidzein amount of 46%. Daidzein release and further conversion into equol were observed during in vitro colonic studies with fecal microbiota from a healthy non-equol-producing donor and Slackia equolifaciens. The developed approach has potential for encapsulating other hydrophobic nutraceuticals or therapeutics, enhancing their bioaccessibility in the colon.

Improving Bioaccessibility and Bioavailability of Isoflavone Aglycones from Chickpeas by Germination and Forming β-Cyclodextrin Inclusion Complexes

Chickpea isoflavones have diverse pharmacological activities but with low water solubility and bioavailability. In this work, the isoflavone content in chickpeas was first increased by germination, and then the bioaccessibility and bioavailability of isoflavones in chickpea sprout extracts (CSE) were enhanced using β-cyclodextrin (β-CD) inclusion techniques. Firstly, the total content of isoflavones was increased by 182 times through sprouting, and isoflavones were presented mostly in the germ and radicle. Then, the chickpea sprout extract/β-cyclodextrin (CSE/β-CD) inclusion complex was prepared and characterized. The in vitro test showed that the cumulative release of two isoflavones, formononetin (FMN) and biochanin A (BCA), in the CSE/β-CD was significantly increased in a simulated digestive fluid. The in vivo rat pharmacokinetics demonstrated that the inclusion of FMN and BCA by β-CD effectively increased their bioavailability in rat plasma and tissues, especially in the liver. The study provides a feasible strategy for improving the bioavailability of isoflavones from chickpeas and is also beneficial to the utilization of other legume resources.

A UPLC-MS/MS Based Rapid, Sensitive, and Non-Enzymatic Methodology for Quantitation of Dietary Isoflavones in Biological Fluids

Dietary isoflavones, a type of phytoestrogens, have gained importance owing to their health-promoting benefits. However, the beneficial effects of isoflavones are mediated by smaller metabolites produced with the help of gut bacteria that are known to metabolize these phytoestrogenic compounds into Daidzein and Genistein and biologically active molecules such as S-Equol. Identifying and measuring these phytoestrogens and their metabolites is an important step towards understanding the significance of diet and gut microbiota in human health and diseases. We have overcome the reported difficulties in quantitation of these isoflavones and developed a simplified, sensitive, non-enzymatic, and sulfatases-free extraction methodology. We have subsequently used this method to quantify these metabolites in the urine of mice using UPLC-MS/MS. The extraction and quantitation method was validated for precision, linearity, accuracy, recoveries, limit of detection (LOD), and limit of quantification (LOQ). Linear calibration curves for Daidzein, Genistein, and S-Equol were set up by performing linear regression analysis and checked using the correlation coefficient (r2 > 0.995). LOQs for Daidzein, Genistein, and S-Equol were 2, 4, and 2 ng/mL, respectively. This UPLC-MS/MS swift method is suitable for quantifying isoflavones and the microbial-derived metabolite S-Equol in mice urine and is particularly useful for large numbers of samples.

Bioaccessibility Evaluation of Soymilk Isoflavones with Biotransformation Processing

Soy isoflavones are considered important sources of bioactive compounds, but they are poorly absorbable, due to their large hydrophilic structures. Some biotransformation strategies have been used to convert the glycosidic form into aglycones, making them available for absorption. This study evaluated the potential of enzymatic and/or microbial fermentation combined bioprocesses in a soymilk extract before and after gastrointestinal in vitro digestion. Commercial β-glucosidase (ET) and a mix of commercial probiotics (F) containing Lactobacillus acidophilus, Lactobacillus casei, Lactococcus lactis, Bifidobacterium bifidum, and Bifidobacterium lactis were used to biotransform the soymilk phenolic extract. An isoflavone profile was identified using HPLC-DAD, total phenolic content was identified using the Folin-Ciocalteu test, and antioxidant capacity was identified using ORAC and FRAP. Soymilk enzymatically treated (ET) followed by microbial fermentation (ET + T) resulted in better conversion of glycosylated isoflavones (6-fold lower than control for daidzin and 2-fold for genistin) to aglycones (18-fold greater than control for dadzein and genistein). The total phenolic content was increased (3.48 mg/mL for control and 4.48 mg/mL for ET + T) and the antioxidant capacity was improved with treatments of ET + T (120 mg/mL for control and 151 mg/mL with ORAC) and with FRAP (285 µL/mL for control and 317 µL/mL). After the in vitro digestion, ET + T samples resulted in a higher content of genistein (two-fold higher than control); also, increases in the total phenolic content (2.81 mg/mL for control and 4.03 mg/mL for ET + T) and antioxidant capacity measured with ORAC were greater compared to undigested samples. In addition, the isolated microbial fermentation process also resulted in positive effects, but the combination of both treatments presented a synergistic effect on soy-based products.

Biotransformation and bioaccessibility of active ingredients from Radix Astragali by Poria cocos during solid-state fermentation and in vitro digestion and antioxidant activity evaluation

Radix Astragali is one of the most famous and frequently used health food supplements and herbal medicines. Among more than 227 components of Radix Astragali, Astragaloside IV (AG IV) is famous functional compound and is commonly used as a quality marker for Radix Astragali. However, the relatively low content of AG IV in Radix Astragali (< 0.04%, w/w) severely limits its application. The purpose of this study is to improve the biotransformation of AG IV and its bioaccessibility during in vitro digestion by Poria cocos solid fermenting Radix Astragali. The optimum fermentation conditions were as follows: Inoculation amount 8 mL; fermentation time 10 d; fermentation humidity 90%. Through fermentation, the content of AG IV was increased from 384.73 to 1986.49 μg/g by 5.16-fold. After in vitro digestion, the contents of genistin, calycosin, formononetin, AG IV, Astragaloside II (AG II) and total flavonoids in fermented Radix Astragali (FRA) of enteric phase II (ENTII) were 34.52 μg/g, 207.32 μg/g, 56.76 μg/g, 2331.46 μg/g, 788.31 μg/g, 3.37 mg/g, which were 2.08-fold, 2.51-fold, 1.05-fold, 8.62-fold, 3.22-fold and 1.50-fold higher than those of control, respectively. The Scanning electron microscopy (SEM) of FRA showed rough surface and porous structure. The DPPH and ABTS radical scavenging rate of FRA were higher than those of control. These results showed that the Poria cocos solid fermentation could increase the content of the AG IV in Radix Astragali and improve the bioaccessibility and antioxidant activity of Radix Astragali, which is providing new ideas for future development and utilization of Radix Astragali.

Acidic natural deep eutectic solvents as dual solvents and catalysts for the solubilization and deglycosylation of soybean isoflavone extracts: Genistin as a model compound

This study investigated the possibility of using green solvent natural deep eutectic solvents (NADESs) as dual solvent-catalysts for the solubilization and deglycosylation of soybean isoflavones. The deglycosylation behavior of genistin as a model compound in NADESs was compared. Acidic NADESs showed moderate solubility for genistin and could hydrolyze it to form genistein. The onset temperature of deglycosylation in the choline chloride/malic acid (Ch-Ma) was 60 °C. The solubilities of genistin in the Ch-Ma system were modeled. The dissolution process was endothermic and mainly enthalpy-driven. The deglycosylation followed first-order kinetics with a half-life (t_1/2) of 40 min at 90 °C. The method was validated using soybean isoflavone extracts as a substrate and the ratio of glycoside to aglycone in the extracts could be adjusted by changing the conditions. The methods have great potential in the extraction and preparation of ready-to-use isoflavone extracts from soybean and other legumes.

Microbial Community Variations and Bioconversion Improvements during Soybean-Based Fermentation by Kefir Grains

Soybeans possess unexpected flavors and are difficult to be absorbed by the gastrointestinal tract. Kefir grain fermentation provides diverse strains and bioactive compounds, which may enhance flavor and bioaccessibility. Third-generation sequencing was applied to analyze the microbial diversity in milk and soybean kefir grains in this study. In both types of kefir grains, the most common bacterial genus was Lactobacillus, and their fungal communities were dominated by Kazachstania. Lactobacillus kefiranofaciens was the most abundant species in kefir grains, while Lactobacillus kefiri showed a higher proportion in soybean kefir grains. In addition, the quantification of free amino acids and volatile flavor compounds in soybean solution and soybean kefir have shown the increased content of glutamic acid and a decreased amount of unpleasant beany flavor compounds, demonstrating that the nutritive value and sensory properties of soybean can be improved by kefir grain fermentation. Finally, the bioconversion of isoflavones during fermentation and in vitro digestion was evaluated, suggesting that fermentation is beneficial for aglycone formation and absorption. To conclude, kefir fermentation is proposed to change the microbial structure of kefir grains, promote the nutritional value of soybean-based fermented products, and provide possible solutions for the development of soybean products.

Current perspectives on the anti-inflammatory potential of fermented soy foods

Fermented soy foods (FSF) are gaining significant attention due to promising health benefits. In recent years, FSF are being studied extensively due to the presence of diverse functional ingredients including active isoflavones and peptides along with essential micronutrients. The process of fermentation is responsible for the enrichment of various bioactive principles in soy-based fermented foods and exclusion of some anti-nutrient factors which are found predominantly in raw soybeans. Emerging evidence suggests that FSF possess immense therapeutic potential against inflammation and associated pathological complications. Extracts prepared from various FSF (e.g. fermented soy paste, milk, and sauce) were found to exert promising anti-inflammatory effects in numerous in vitro and in vivo settings. Moreover, clinical findings highlighted an inverse relationship between consumption of FSF and the prevalence of chronic inflammatory disorders among the communities which habitually consume fermented soy products. Molecular mechanisms underlying the anti-inflammatory role of FSF have been delineated in many literatures which collectively suggest that FSF extracts have regulatory actions over the expression and/or activity of several proinflammatory cytokines, inflammatory mediators, oxidative stress markers, and some other factors involved in the inflammatory pathways. The present review discusses the anti-inflammatory effects of FSF with mechanistic insights based upon the available findings from cell culture, preclinical, and clinical investigations.

An Optical Sensing Platform for Beta-Glucosidase Activity Using Protein-Inorganic Hybrid Nanoflowers

In this work, a convenient and dual-signal readout optical sensing platform for the sensitively and selectively determination of beta-glucosidase (β-Glu) activity was reported using protein-inorganic hybrid nanoflowers [BSA-Cu₃(PO₄)₂·3H₂O] possessing peroxidase-mimicking activity. The nanoflowers (NFs) were facilely synthesized through a self-assembled synthesis strategy at room temperature. The as-prepared NFs could catalytically convert the colorless and non-fluorescent Amplex Red into colored and highly fluorescent resorufin in the presence of hydrogen peroxide via electron transfer process. β-Glu could hydrolyze cyanogenic glycoside, using amygdalin (Amy) as a model, into cyanide ions (CN^-), which can subsequently efficiently suppress the catalytic activity of NFs, accompanied with the fluorescence decrease and the color fading. The concentration of CN^- was controlled by β-Glu-triggered enzymatic reaction of Amy. Thus, a sensing system was established for fluorescent and visual determination of β-Glu activity. Under the optimum conditions, the present fluorescent and visual bimodal sensing platform exhibited good sensitivity for β-Glu activity assay with a detection limit of 0.33 U·L^-1. The sensing platform was further applied to determinate β-Glu in real samples and satisfactory results were attained. Additionally, the optical sensing system can potentially be a promising candidate for β-Glu inhibitors screening.

The roles of brewers’ spent grain derivatives in coconut-based yogurt-alternatives: Microstructural characteristic and the evaluation of physico-chemical properties during the storage

Water soluble coconut extract (WSCE) was reported as a suitable matrix for probiotic delivery as yogurt alternatives. The study aimed to evaluate the roles of brewers’ spent grain (BSG) derivatives in enhancing the properties of WSCE-based yogurt alternatives. BSG flour (BSGF) and 3 different protein extracts (BSGPs) including protein control (BSGP-C), protamex treatment (BSGP-P), and protamex combined with flavourzyme treatment (BSGP-PF) were incorporated in WSCE-based yogurt alternatives. Confocal laser scanning microscopy showed that BSGPs prepared with protease treatment generated less dense fat distribution and more homogenous globules compared to that in WSCE control yogurt. It also resulted in a softer, denser and more homogenous matrix. The modification in microstructural properties was aligned with differences in several functional groups including ⍺-glycosidic bond and hydroxyl groups from polysaccharides, aliphatic ethers and acid functional groups as well as aromatic hydrocarbons of lignin, amide I, acetyl groups and amide III. BSGF and BSGPs increased the mechanical properties, viscosity and modified flow behaviour properties demonstrating its ability in maintaining textural and gel formation. After 14 days of storage, maintenance in flow behaviour, syneresis and mechanical properties was identified. Furthermore, BSG derivatives enhanced lactic acid production up to 3 folds. In conclusion, BSG derivatives maintained the microstructure and gel formation, improved the properties of WSCE-based yogurt alternatives and preserved its behaviour during 14 days of storage.

•

BSG derivatives maintained the microstructural of coconut-based yogurt alternatives.

•

BSG derivatives improved the physical behaviour of WSCE yogurt alternatives.

•

BSG derivatives enhanced lactic acid content in WSCE-based yogurt alternatives.

Effects of enzyme-assisted extraction on the profile and bioaccessibility of isoflavones from soybean flour

The effects of enzymatic extraction strategies on extractability, bioconversion, and bioaccessibility of biologically active isoflavone aglycones, total phenolic content, and antioxidant activity of aqueous extracts from full-fat soy flour were evaluated. Protease, tannase, and cellulase enzymes were used individually or in combination. Except for the protease treatment, all enzymatic treatments increased the extraction of biologically active isoflavones (daidzein and genistein) compared with the control. The use of a mixture of protease, tannase, and cellulase resulted in increased extractability and/or bioconversion of aglycones from soy flour, indicating a synergistic effect amongst the enzymes. Daidzein and genistein concentrations increased from 29.0 to 158.2 μg/g and from 27.0 to 156.5 μg/g (compared to the control), respectively. Furthermore, enzymatic extraction followed by in vitro gastrointestinal digestion significantly increased the bioaccessibility of isoflavone aglycones, total phenolic content (by 22-45%), and antioxidant activity (by 15-22%) of the extracts. These results demonstrate that enzyme selection is an efficient strategy to maximize the extraction, bioconversion, and bioaccessibility of bioactive isoflavones from soy flour, which could contribute to health benefits associated with the consumption of soy-rich products.