A novel isoflavone profiling method based on UPLC-PDA-ESI-MS

Identification of Fouling Occurring during Coupled Electrodialysis and Bipolar Membrane Electrodialysis Treatment for Tofu Whey Protein Recovery

Tofu whey, a by-product of tofu production, is rich in nutrients such as proteins, minerals, fats, sugars and polyphenols. In a previous work, protein recovery from tofu whey was studied by using a coupled environmental process of ED + EDBM to valorize this by-product. This process allowed protein recovery by reducing the ionic strength of tofu whey during the ED process and acidifying the proteins to their isoelectric point during EDBM. However, membrane fouling was not investigated. The current study focuses on the fouling of membranes at each step of this ED and EDBM process. Despite a reduction in the membrane conductivities and some changes in the mineral composition of the membranes, no scaling was evident after three runs of the process with the same membranes. However, it appeared that the main fouling was due to the presence of isoflavones, the main polyphenols in tofu whey. Indeed, a higher concentration was observed on the AEMs, giving them a yellow coloration, while small amounts were found in the CEMs, and there were no traces on the BPMs. The glycosylated forms of isoflavones were present in higher concentrations than the aglycone forms, probably due to their high amounts of hydroxyl groups, which can interact with the membrane matrices. In addition, the higher concentration of isoflavones on the AEMs seems to be due to a combination of electrostatic interactions, hydrogen bonding, and π-π stacking, whereas only π-π stacking and hydrogen bonds were possible with the CEMs. To the best of our knowledge, this is the first study to investigate the potential fouling of BPMs by polyphenols, report the fouling of IEMs by isoflavones and propose potential interactions.

Comprehensive characterization of flavonoid derivatives in young leaves of core-collected soybean (Glycine max L.) cultivars based on high-resolution mass spectrometry

Most previous studies have been focused on isoflavone profile with biological activities from soybean seed and its related products. However, in the present study, eighty-three flavonoid derivatives (55 flavonols, 9 flavones and 19 isoflavones) were comprehensively identified and quantified from young leaves of 21 core-collected soybean cultivars based on ultra-performance liquid chromatography-diode array detector with quadrupole time of flight/mass spectrometry (UPLC-DAD-QToF/MS). Among total flavonoids from soybean leaves (SLs), the abundant flavonols (83.6%) were primarily composed of di- and tri- glycosides combined to the aglycones (K, kaempferol; Q, quercetin; I, isorhamnetin). Particularly, K-rich SLs (yellow coated seed), Nongrim 51 (breeding line) and YJ208-1 (landrace) contained mainly kaempferol 3-O-(2″-O-glucosyl-6″-O-rhamnosyl)galactoside and 3-O-(2″,6″-di-O-rhamnosyl)galactoside, and were expected to be superior cultivars by their higher flavonoids. Besides, the new tri-I-glycosides (soyanins I–V) were presented as predominant components in Junyeorikong (landrace, black). Thus, this study suggest that the SLs can be considered as valuable edible resources due to their rich flavonoids. Also, these detailed profiles will support breeding of superior varieties with excellent biological activities as well as relationship with seed anthocyanins production, and contribute to perform metabolomics approach to investigate the changes of SLs flavonols during the leaf growth and fermentation in further research.

Separation of soy isoflavones from soy sauce residue by MIL-100(Fe)

Soy sauce residue (SSR) is a valuable biological resource, which contains soy isoflavones (SIs) with antioxidant activity and can be used to scavenge radicals. Herein, MIL-100(Fe) was synthesized for the extraction of SIs from SSR. Under the optimal adsorption conditions, the adsorption capacity of MIL-100(Fe) for SIs was 51.81 mg/g, which could achieve a purity of 56.17% and a recovery of 93.8%. These results demonstrated MIL-100(Fe) possessed effective properties of adsorption and purification for SIs. The content of SIs in the purified product was 167 times than that of SSR. The purified total SIs had a good antioxidant activity. The established method had a good scavenging ability toward 2, 2-diphenyl-1-picrylhydrazyl, superoxide and hydroxyl radicals, with IC₅₀ values of 0.177, 0.116 and 0.082 mg/mL, respectively. Besides, the ferrous ion chelating potency was better than others, with IC₅₀ values of 0.63 ± 0.0044 mg/mL. The established method was suitable for large-scale separation of purified total SIs and provided a reference for purification of bioactive factors from complex substrates.

Changes in Isoflavone Profile from Soybean Seeds during Cheonggukjang Fermentation Based on High-Resolution UPLC-DAD-QToF/MS: New Succinylated and Phosphorylated Conjugates

In this study, thirty-eight isoflavone derivatives were comprehensively identified and quantified from the raw, steamed and fermented seeds of four selected soybean cultivars based on UPLC-DAD-QToF/MS results with reference to the previously reported LC-MS library and flavonoid database, and summarized by acylated group including glucosides (Glu), malonyl-glucosides (Mal-Glu), acetyl-glucosides (Ac-Glu), succinyl-glucosides (Suc-Glu) and phosphorylated conjugates (Phos) in addition to aglycones. Among them, Suc-Glu and Phos derivatives were newly generated due to fermentation by B. subtilis AFY-2 (cheonggukjang). In particular, Phos were characterized for the first time in fermented soy products using Bacillus species. From a proposed roadmap on isoflavone-based biotransformation, predominant Mal-Glu (77.5-84.2%, raw) decreased rapidly by decarboxylation and deesterification into Ac-Glu and Glu (3.5-8.1% and 50.0-72.2%) during steaming, respectively. As fermentation continued, the increased Glu were mainly succinylated and phosphorylated as well as gradually hydrolyzed into their corresponding aglycones. Thus, Suc-Glu and Phos (17.3-22.4% and 1.5-5.4%, 36 h) determined depending on cultivar type and incubation time, and can be considered as important biomarkers generated during cheonggukjang fermentation. Additionally, the changes of isoflavone profile can be used as a fundamental report in applied microbial science as well as bioavailability research from fermented soy foods.

A new isoflavone glucoside and other compounds from Poiretia bahiana C. Mueller: Chemophenetics, fragmentation pattern and biogenetic implications

The genus Poiretia belongs to the Fabaceae (Leguminosae) family and it encompasses twelve species of flowering plants. The chemistry of this genus is scarcely investigated, although some studies have demonstrated the potential of Poiretia species to produce important bioactive compounds. Herein, we describe the phytochemical investigation of P. bahiana C. Mueller leaves. A new isoflavone glucoside named as 2',4',5'-trimethoxyisoflavone-7-O-β-D-glucopyranoside (1), along with six known isoflavones (2-7), two rotenones (8-9), cyclitol 3-O-methyl-chiro-inositol (10), the amino acid proline (11), a mixture of sitosterol (12) and stigmasterol (13), and a mixture of the triterpenes lupeol (14) and β-amirine (15) were obtained from P. bahiana leaves. The structures were established by extensive analysis of their spectroscopic data, which included ¹H NMR, ¹³C NMR, DEPT, and 2D-NMR (¹³C¹H HETCOR and ¹³C¹H COLOC). Two isoflavones (3 and 5) and two rotenones (8-9) exhibited antifungal activity against the plant pathogenic fungus Cladosporium sphaerospermum. Furthermore, the biogenetic implications of the oxygenation pattern of the B-ring of the isoflavones, and the chemophenetics and fragmentation pattern of the isoflavones and rotenones are discussed.

Steam flash explosion pretreatment enhances soybean seed coat phenolic profiles and antioxidant activity

The resource utilization of soybean seed coats is currently poor. In this study, steam flash explosion (SFE) pretreatment was performed to extract valuable phytochemicals from soybean seed coats. The total content of phytochemicals and the antioxidant activity of extracts from SFE-treated soybean seed coat were systematically evaluated. On the basis of the application value of antioxidant activity, we optimized the process parameters of SFE-pretreated soybean seed coat to maximize the antioxidant activity. Additionally, the subsequently obtained ethyl acetate fraction with the highest antioxidant activity was analysed using HPLC-DAD-Q-Orbitrap HRMS/MS analysis. The results indicated that SFE could enhance the release of both aglycone and acetylglucoside forms of isoflavones from the cellular structure and enhance the antioxidant activity of soybean seed coats. This study provides evidence that SFE is a novel thermal processing technology with high efficiency and low energy consumption that improves the phytochemical composition and bioactivity of soybean seed coats.

pH-adjusted solvent extraction and reversed-phase HPLC quantification of isoflavones from soybean (Glycine max (L.) Merr.)

Soybeans, Glycine max (L.) Merr., are among the most important food crops worldwide. Isoflavones are major bioactive phytochemicals in soybeans, and have a variety of health benefits, including antioxidative, antiatherosclerotic, antiinflammatory, and weak estrogen-like effects. The isoflavone content and composition of soybeans vary according to the cultivar and the extraction solvent conditions. Therefore, we investigated the effects of three different solvent pHs (1.0, 5.5, and 10.0) on the isoflavone, total phenolic, and total flavonoid contents and antioxidant capacities of eight soybean cultivars developed in Korea. Twelve isoflavones in soybeans were efficiently separated and identified on a reversed-phase high-performance liquid chromatography (HPLC) system. The percentage distribution of isoflavones measured by HPLC in the eight soybean cultivars at various extraction pHs decreased as follows: malonyl isoflavones (67.2% to 81.3%) > isoflavone glucosides (16.2% to 29.0%; as nonacylated form) > acetyl isoflavones (1.6% to 5.9%). The highest contents of isoflavone glucosides, malonyl derivatives, and acetyl derivatives were extracted at solvent pHs of 10.0, 1.0, and 5.5, respectively. The solvent extraction at pH 1.0 yielded a lower total isoflavone content than those at pHs 5.5 and 10.0. However, the highest total phenolic and flavonoid contents were extracted from soybeans at pH 1.0. Soybeans extracted at pH 10.0 displayed the highest antioxidant capacities in the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical assay. Taken together, these results suggest that proper solvent pH adjustment is needed to maximize the extraction of targeted forms of isoflavones from soybeans. PRACTICAL APPLICATION: Soybeans contain a variety of bioactive compounds, including isoflavones, which function as antioxidants and weak phytoestrogens. Chemical and instrumental analyses can facilitate the selection of soybean cultivars with high amounts of isoflavones for soybean breeding and isoflavone-enriched product development. Proper solvent pH adjustment allows for the efficient extraction of high amounts of targeted isoflavone subgroups (acetyl and malonyl forms) from soybeans for functional food products.

Effects of Different Oligochitosans on Isoflavone Metabolites, Antioxidant Activity, and Isoflavone Biosynthetic Genes in Soybean ( Glycine max) Seeds during Germination

Five oligochitosans with increasing degrees of polymerization (DPs), i.e., from chitotriose to chitoheptaose, were examined to clarify the structure-bioactivity relationship between the DPs of oligochitosans and their effects on the isoflavone metabolites, total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activity of soybean ( Glycine max) seeds during germination. Oligochitosans of different DPs exhibited varying influences on the TPC, TFC, and antioxidant activities of soybean seeds. Chitohexaose exerted a strong effect and significantly increased the aforementioned parameters in soybean seeds 72 h after germination. Genistin, malonylgenistin, and genistein were the main isoflavones found, and the genistin and genistein contents were significantly enhanced by 67.32% and 131.38%, respectively, after chitohexaose treatment. Several critical genes involved in the isoflavone biosynthesis (i.e., PAL, CHS, CHI, IFS) of soybeans treated with and without chitohexaose were analyzed, and results suggested that chitohexaose application could dramatically stimulate the transcription of these genes.

Soy Isoflavones and their Effects on Xenobiotic Metabolism

BACKGROUND

Soy isoflavones, such as genistein and daidzein, are bioflavonoids found in soy products that are able to interact with various hormones such as estrogen. Epidemiological studies reveal a proper level of isoflavones in diet can prevent many diseases like cancers or diabetes. Therefore, it is important to study the biotransformation and xenobiotic metabolism of soy isoflavones.

METHODS

A systematic review of published studies was carried out to investigate the characterization of isoflavones and their metabolites, sample pretreatment and quantitative analysis of isoflavones, and the influence of soy isoflavones on drug and xenobiotic metabolism.

RESULTS

Aglycones with weak estrogen-like activities are the biologically active forms of the soy isoflavones in mammals. The most recent advances including extraction, purification and detection of isoflavones in soybean and soy products are discussed. The effects of soy isoflavones on drug and xenobiotic metabolism involve in regulation of phase I cytochrome P450 (CYPs) enzyme and phase I detoxifying enzymes expression and activity. At the molecular level, soy isoflavones have proved capable of estrogenic/antiestrogenic with tissue-selective, anti-cancer, antiobesity, anti-oxidation, and tyrosine kinase inhibition activities.

CONCLUSION

This review summarized different aspects of soy isoflavones and their molecular mechanisms of pharmacological action on xenobiotic, which demonstrated that soy isoflavones can decrease the incidence of many diseases and benefit for human health. However, since the lack of clinical research for evaluation of the proper dosage of intake of soy isoflavones in diet or adjunctive therapy, there is a need for further studies on the selection of doses, biomedical applications and adverse effects of isoflavones for human health.