Bioconversion of Flavonoid Glycosides from Hippophae rhamnoides Leaves into Flavonoid Aglycones by Eurotium amstelodami

Effects of inoculation and dry matter content on microbiome dynamics and metabolome profiling of sorghum silage

Sorghum forage was ensiled for 90 days at two dry matter (DM) contents (27 vs. 39%) without or with Lactiplantibacillus plantarum inoculation. On day 90 of fermentation, silages were sampled to assess the microbial community dynamics and metabolome profile. L. plantarum inoculation improved silage quality, as shown by a lower pH and greater acetic acid concentration. Loss of DM remained unaffected by L. plantarum inoculation but was greater in low- vs. high-DM sorghum silages (14.4 vs. 6.62%). The microbiome analysis revealed that Pseudomonas congelans represented the dominant species of the epiphytic microbiota in both low- and high-DM sorghum forage before ensiling. However, L. buchneri represented the dominant species at the end of ensiling. Ensiling fermentation resulted in distinct metabolic changes in silages with varying DM content. In low-DM silages, ensiling fermentation led to the accumulation of 24 metabolites and a reduction in the relative concentration of 13 metabolites. In high-DM silages, ensiling fermentation resulted in an increase in the relative concentration of 26 metabolites but a decrease in the concentration of 8 metabolites. Compared to non-inoculated silages, L. plantarum inoculation resulted in an increased concentration of 3 metabolites and a reduced concentration of 5 metabolites in low-DM silages. Similarly, in high-DM silages, there was an elevation in the relative concentration of 3 metabolites, while a decrease in 7 other metabolites. Ten metabolites with bio-functional activity were identified, including chrysoeriol, isorhamnetin, petunidin 3-glucoside, apigenin, caffeic acid, gallic acid, p-coumaric acid, trans-cinnamic acid, herniarin, and 3,4-dihydroxy-trans-cinnamate. This study presents a comprehensive analysis of microbiome and metabolome profiling of sorghum forage during ensiling as a function of DM content and L. plantarum inoculation, with a particular emphasis on identifying metabolites that may possess bio-functional properties. KEY POINTS: • DM loss was not different by L. plantarum but higher in low- vs. high-DM silage. • L. buchneri dominated ensiling, regardless of DM level. • 10 metabolites with bio-functional activity were identified.

New insights of flavonoid glycosidases and their application in food industry

Flavonoids are significant natural nutraceuticals and a key component of dietary supplements. Given that flavonoid glycosides are more plentiful in nature and less beneficial to human health than their aglycone counterparts, they serve as potential precursors for flavonoid production. Glycosidases have shown substantial potential within the food industry, particularly in enhancing the organoleptic properties of juice, wine, and tea. When applied to food resources, glycosidases can amplify their biological activities, thereby improving the performance of functional foods. This review provides up-to-date information on flavonoid glycosidases, including their catalytic mechanisms, biochemical properties, and natural sources, as well as their applications within the food industry. The use of flavonoid glycosidases in improving food quality is also reviewed.

Effects of Fermentation on Bioactivity and the Composition of Polyphenols Contained in Polyphenol-Rich Foods: A Review

Polyphenols, as common components with various functional activities in plants, have become a research hotspot. However, researchers have found that the bioavailability and bioactivity of plant polyphenols is generally low because they are usually in the form of tannins, anthocyanins and glycosides. Polyphenol-rich fermented foods (PFFs) are reported to have better bioavailability and bioactivity than polyphenol-rich foods, because polyphenols are used as substrates during food fermentation and are hydrolyzed into smaller phenolic compounds (such as quercetin, kaempferol, gallic acid, ellagic acid, etc.) with higher bioactivity and bioavailability by polyphenol-associated enzymes (PAEs, e.g., tannases, esterases, phenolic acid decarboxylases and glycosidases). Biotransformation pathways of different polyphenols by PAEs secreted by different microorganisms are different. Meanwhile, polyphenols could also promote the growth of beneficial bacteria during the fermentation process while inhibiting the growth of pathogenic bacteria. Therefore, during the fermentation of PFFs, there must be an interactive relationship between polyphenols and microorganisms. The present study is an integration and analysis of the interaction mechanism between PFFs and microorganisms and is systematically elaborated. The present study will provide some new insights to explore the bioavailability and bioactivity of polyphenol-rich foods and greater exploitation of the availability of functional components (such as polyphenols) in plant-derived foods.

Flavonoids from Seabuckthorn (Hippophae rhamnoides L.) mimic neurotrophic functions in inducing neurite outgrowth in cultured neurons: Signaling via PI3K/Akt and ERK pathways

BACKGROUND

Various brain disorders, including neurodegenerative diseases and major depressive disorders, threaten an increasing number of patients. Seabuckthorn, a fruit from Hippophae rhamnoides L., is an example of "medicine food homology". The fruit has enriched flavonoids that reported to have benefits in treating cognitive disorders. However, the studies on potential functions of Seabuckthorn and/or its flavonoid-enriched fraction in treating neurodegenerative disorders are limited.

PURPOSE

This study aimed to determine the ability and mechanism of the flavonoid-enriched fraction of Seabuckthorn (named as SBF) in mimicking the neurotrophic functions in inducing neurite outgrowth of cultured neurons.

METHODS

Cultured PC12 cell line, SH-SY5Y cell line and primary neurons (cortical and hippocampal neurons isolated from E17-19 SD rat embryos) were the employed models to evaluate SBF in inducing neurite outgrowth by comparing to the effects of NGF and BDNF. Immuno-fluorescence staining was applied to identify the morphological change during the neuronal differentiation. Luciferase assay was utilized for analyzing the transcriptional regulation of neurofilaments and cAMP/CREB-mediated gene. Western blot assay was conducted to demonstrate the expressions of neurofilaments and phosphorylated proteins.

RESULTS

The application of SBF induced neuronal cell differentiation, and this differentiating activation was blocked by the inhibitors of PI3K/Akt and ERK pathways. Additionally, SBF showed synergy with neurotrophic factors in stimulating the neurite outgrowth of cultured neurons. Moreover, the major flavonoids within SBF, i.e., isorhamnetin, quercetin and kaempferol, could account for the neurotrophic activities of SBF.

CONCLUSION

Seabuckthorn flavonoids mimicked neurotrophic functions in inducing neuronal cell differentiation via activating PI3K/Akt and ERK pathways. The results suggest the beneficial functions of Seabuckthorn as a potential health food supplement in treating various brain disorders, e.g., neurodegenerative diseases.

Upgrading the accumulation of ginsenoside Rd in Panax notoginseng by a novel glycosidase-producing endophytic fungus G11-7

A novel endophytic fungus producing beta-glucosidase was isolated and characterized from pigeon pea (Cajanus cajan [L.] Millsp.), which has excellent properties in converting ginsenoside Rb1 to ginsenoside Rd in Panax notoginseng. According to the 16S rDNA gene sequence, the G11-7 strain was identified as Fusarium proliferatum, and the accession number KY303906 was confirmed in GenBank. The G11-7 immobilized spores, in which the activity of beta-glucosidase could reach 0.95 U/mL, were co-cultured with P. notoginseng plant material to obtain a continuous beta-glucosidase supply for the biotransformation of ginsenoside Rb1 to Rd. Under the liquid-solid ratio (20:1), initial pH (6.0), and temperature (30 °C) constituents, the maximum ginsenoside Rd yield was obtained as 9.15 ± 0.65 mg/g, which was 3.67-fold higher than that without fungal spore co-culture (2.49 ± 0.98 mg/g). Furthermore, immobilized G11-7 spores showed significant beta-glucosidase producing ability which could be recovered and reused for 6 cycles. Overall, these results suggested that immobilized G11-7 offered a promising and effective approach to enhance the production of ginsenoside Rd for possible nutraceutical and pharmaceutical uses.

The Spectrum of Pharmacological Actions of Syringetin and Its Natural Derivatives-A Summary Review

Mono- and poly-O-methylated flavonols and their glycoside derivatives belong to the group of natural plant polyphenols with a wide spectrum of pharmacological activities. These compounds are known for their antioxidant, antimutagenic, hepatoprotective, antidiabetic, and antilipogenic properties. Additionally, they inhibit carcinogenesis and cancer development. Having in mind the multidirectional biological activity of methylated flavonols, we would like to support further study on their health-promoting activities; in this review we summarized the most recent reports on syringetin and some of its structural analogues: laricitrin, ayanin, and isorhamnetin. Natural sources and biological potential of these substances were described based on the latest research papers.

Microbial Bioconversion of Phenolic Compounds in Agro-industrial Wastes: A Review of Mechanisms and Effective Factors

Agro-industrial wastes have gained great attention as a possible source of bioactive compounds, which may be utilized in various industries including pharmaceutics, cosmetics, and food. The food processing industry creates a vast amount of waste which contains valuable compounds such as phenolics. Polyphenols can be found in soluble (extractable or free), conjugated, and insoluble-bound forms in various plant-based foods including fruits, vegetables, grains, nuts, and legumes. A substantial portion of phenolic compounds in agro-industrial wastes is present in the insoluble-bound form attached to the cell wall structural components and conjugated form which is covalently bound to sugar moieties. These bound phenolic compounds can be released from wastes by hydrolysis of the cell wall and glycosides by microbial enzymes. In addition, they can be converted into unique metabolites by methylation, carboxylation, sulfate conjugation, hydroxylation, and oxidation ability of microorganisms during fermentation. Enhancement of concentration and antioxidant activity of phenolic compounds and production of new metabolites from food wastes by microbial fermentation might be a promising way for better utilization of natural resources. This review provides an overview of mechanisms and factors affecting release and bioconversion of phenolic compounds in agro-industrial wastes by microbial fermentation.

Metabolite profiling, antioxidant and α-glucosidase inhibitory activities of buckwheat processed by solid-state fermentation with Eurotium cristatum YL-1

Buckwheat was processed by solid-state fermentation (SSF) with the probiotic fungal strain Eurotium cristatum YL-1. The effects of SSF on the phytochemical content, as well as the antioxidant and α-glucosidase inhibitory activities, on buckwheat were revealed. Metabolite differences between non-fermented buckwheat (BW) and E. cristatum fermented buckwheat (FBW) were investigated by LC-MS/MS-based untargeted metabolomics. Results showed that 103 and 68 metabolites remarkably differed between BW and FBW in positive and negative ionization modes, respectively. Most phenolic compounds and alkaloids were significantly up-regulated during SSF. Hydrolytic enzymes (i.e., β-glucosidase, α-amylase, protease, and cellulase) were produced by the filamentous fungus E. cristatum during SSF. In vitro spectrophotometric assays demonstrated that the total phenolics content, ferric reducing antioxidant power, reducing power, scavenging activities of DPPH radical and ABTS⁺, and α-glucosidase inhibitory activity of buckwheat were considerably enhanced after processing by SSF with E. cristatum. Additionally, solvents with different polarities significantly influenced the antioxidant and α-glucosidase inhibitory activities of buckwheat extracts. Our study indicated that processing by SSF with E. cristatum can greatly improve the phytochemical components of buckwheat and consequently contribute to its antioxidant and α-glucosidase inhibitory activities. SSF with E. cristatum is an innovative method for enhancing the health-promoting components and bioactivities of buckwheat.

Influence of Harvest Date and Postharvest Treatment on Carotenoid and Flavonoid Composition in French Marigold Flowers

The aim of this study was to characterize carotenoids and flavonoids present in French marigold flowers (Tagetes patula "Durango Red") as well as to assess the effects of harvest dates and postharvest treatments on these compounds. Carotenoids and flavonoids were quantified using their respective standards or semiquantified using relevant related standards. Lutein and its derivatives largely dominated the flower carotenoids, while the flavonoids were diverse with patuletin leading the list. Of the different postharvest treatments, ensilage leads to the highest content of carotenoids (from 5.0 to 7.8 g kg^-1 dw) and flavonoids (from 19 to 50 g kg^-1 dw). The composition of individual flavonoids was greatly influenced by different postharvest treatments, while the influence of harvest dates was secondary. Ensilage and drying induced separate metabolic pathways leading to degradation of high-molecular glycosidic compounds, converting the compounds either to their aglycones or into the intermediate flavonoid glycosides. We conclude that according to the intended industrial application, different postharvest techniques can be employed to acquire desired flavonoids on a large scale.

Inhibitory Effects of Eurotium cristatum on Growth and Aflatoxin B1 Biosynthesis in Aspergillus flavus

Probiotic strain Eurotium cristatum was isolated from Chinese Fuzhuan brick-tea and tested for its in vitro activity against aflatoxigenic Aspergillus flavus. Results indicated that E. cristatum can inhibit the radial growth of A. flavus. Furthermore, this inhibition might be caused by E. cristatum secondary metabolites. The ability of culture filtrate of strain E. cristatum against growth and aflatoxin B₁ production by toxigenic A. flavus was evaluated in vitro. Meanwhile, the influence of filtrate on spore morphology of A. flavus was analyzed by scanning electron microscopy (SEM). Results demonstrated that both radial growth of A. flavus and aflatoxin B₁ production were significantly weakened following increases in the E. cristatum culture filtrate concentration. In addition, SEM showed that the culture filtrate seriously damaged hyphae morphology. Gas chromatography mass spectrometry (GC/MS) analysis of the E. cristatum culture supernatant revealed the presence of multiple antifungal compounds. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis showed that the expression of aflatoxin biosynthesis-related genes (aflD, aflQ, and aflS) were down-regulated. Importantly, this latter occurrence resulted in a reduction of the AflS/AflR ratio. Interestingly, cell-free supernatants of E. cristatum facilitated the effective degradation of aflatoxin B₁. In addition, two degradation products of aflatoxin B₁ lacking the toxic and carcinogenic lactone ring were identified. A toxicity study on the HepG2 cells showed that the degradation compounds were less toxic when compared with AFB₁.

Flavonoids, terpenoids, and polyketide antibiotics: Role of glycosylation and biocatalytic tactics in engineering glycosylation

Flavonoids, terpenoids, and polyketides are structurally diverse secondary metabolites used widely as pharmaceuticals and nutraceuticals. Most of these molecules exist in nature as glycosides, in which sugar residues act as a decisive factor in their architectural complexity and bioactivity. Engineering glycosylation through selective trimming or extension of the sugar residues in these molecules is a prerequisite to their commercial production as well to creating novel derivatives with specialized functions. Traditional chemical glycosylation methods are tedious and can offer only limited end-product diversity. New in vitro and in vivo biocatalytic tools have emerged as outstanding platforms for engineering glycosylation in these three classes of secondary metabolites to create a large repertoire of versatile glycoprofiles. As knowledge has increased about secondary metabolite-associated promiscuous glycosyltransferases and sugar biosynthetic machinery, along with phenomenal progress in combinatorial biosynthesis, reliable industrial production of unnatural secondary metabolites has gained momentum in recent years. This review highlights the significant role of sugar residues in naturally occurring flavonoids, terpenoids, and polyketide antibiotics. General biocatalytic tools used to alter the identity and pattern of sugar molecules are described, followed by a detailed illustration of diverse strategies used in the past decade to engineer glycosylation of these valuable metabolites, exemplified with commercialized products and patents. By addressing the challenges involved in current bio catalytic methods and considering the perspectives portrayed in this review, exceptional drugs, flavors, and aromas from these small molecules could come to dominate the natural-product industry.

Bioprocessing of soybeans (Glycine max L.) by solid-state fermentation with Eurotium cristatum YL-1 improves total phenolic content, isoflavone aglycones, and antioxidant activity

In this study, soybean (Glycine max L.) was bioprocessed with fungal strain Eurotium cristatum YL-1 by using the solid-state fermentation (SSF) technique. The effect of SSF on total phenolic content (TPC), isoflavone compositions, and antioxidant activity of soybean during different fermentation periods was evaluated. Results showed that TPC and isoflavone aglycones were significantly increased, whereas glucoside isoflavones were remarkably reduced during SSF. After 15 days of SSF, the TPC, daidzein, genistein, and total aglycones of soybeans were approximately 1.9-, 10.4-, 8.4-, and 9.4-fold higher, respectively, than those of non-fermented soybeans. During SSF, β-glucosidase activity was very high, whereas α-amylase and protease activities were at moderate levels, and cellulase activity was relatively low. A highly positive correlation was found between TPC and the activities of α-amylase (correlation coefficient R² = 0.9452), β-glucosidase (R² = 0.9559), cellulase (R² = 0.9783), and protease (R² = 0.6785). Linear analysis validated that the β-glucosidase produced by E. cristatum contributed to the bioconversion of soybean isoflavone glucosides into their aglycone forms. The DPPH radical and ABTS˙⁺ scavenging activity, reducing power, and ferric reducing antioxidant power of soybeans were considerably enhanced during SSF. Principal component analysis and Pearson's correlation analysis verified that the improvement in TPC and isoflavone aglycone content during SSF was mainly responsible for the improved antioxidant capacity of soybeans. Thus, our results demonstrated that solid-state bioprocessing with E. cristatum is an effective approach for the enhancement of the TPC, isoflavone aglycones, and antioxidant capacity of soybeans. Bioprocessed soybean products might be a healthy food supplement rich in antioxidants compared with non-fermented soybean and thus could be a source of natural antioxidants.

Solid-state bioprocessing with Eurotium cristatum is an effective approach for the enhancement of total phenolic content, isoflavone aglycones, and antioxidant activity of soybeans.

In vitro Gastrointestinal Models for Prebiotic Carbohydrates: A Critical Review

Background:

In the last decade, various consortia and companies have created standardized digestion protocols and gastrointestinal simulators, such as the protocol proposed by the INFOGEST Consortium, the simulator SHIME, the simulator simgi®, the TIM, etc. Most of them claim to simulate the entire human gastrointestinal tract. However, few results have been reported on the use of these systems with potential prebiotic carbohydrates.

Methods:

This critical review addresses the existing data on the analysis of prebiotic carbohydrates by different in vitro gastrointestinal simulators, the lack of parameters that could affect the results, and recommendations for their enhancement.

Results:

According to the reviewed data, there is a lack of a realistic approximation of the small intestinal conditions, mainly because of the absence of hydrolytic conditions, such as the presence of small intestinal brush border carbohydrases that can affect the digestibility of different carbohydrates, including prebiotics.

Conclusion:

There is a necessity to standardize and enhance the small intestine simulators to study the in vitro digestibility of carbohydrates.

Isorhamnetin Induces Cell Cycle Arrest and Apoptosis Via Reactive Oxygen Species-Mediated AMP-Activated Protein Kinase Signaling Pathway Activation in Human Bladder Cancer Cells

Isorhamnetin is an O-methylated flavonol that is predominantly found in the fruits and leaves of various plants, which have been used for traditional herbal remedies. Although several previous studies have reported that this flavonol has diverse health-promoting effects, evidence is still lacking for the underlying molecular mechanism of its anti-cancer efficacy. In this study, we examined the anti-proliferative effect of isorhamnetin on human bladder cancer cells and found that isorhamnetin triggered the gap 2/ mitosis (G2/M) phase cell arrest and apoptosis. Our data showed that isorhamnetin decreased the expression of Wee1 and cyclin B1, but increased the expression of cyclin-dependent kinase (Cdk) inhibitor p21^WAF1/CIP1, and increased p21 was bound to Cdk1. In addition, isorhamnetin-induced apoptosis was associated with the increased expression of the Fas/Fas ligand, reduced ratio of B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X protein (Bax) expression, cytosolic release of cytochrome c, and activation of caspases. Moreover, isorhamnetin inactivated the adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling pathway by diminishing the adenosine triphosphate (ATP) production due to impaired mitochondrial function. Furthermore, isorhamnetin stimulated production of intracellular reactive oxygen species (ROS); however, the interruption of ROS generation using a ROS scavenger led to an escape from isorhamnetin-mediated G2/M arrest and apoptosis. Collectively, this is the first report to show that isorhamnetin inhibited the proliferation of human bladder cancer cells by ROS-dependent arrest of the cell cycle at the G2/M phase and induction of apoptosis. Therefore, our results provide an important basis for the interpretation of the anti-cancer mechanism of isorhamnetin in bladder cancer cells and support the rationale for the need to evaluate more precise molecular mechanisms and in vivo anti-cancer properties.