Solubility Of Flavonoids Research Articles

Solubility and extractability enhancement of the main food flavonoids by using choline chloride-based natural deep eutectic solvents

This study investigates the solubility of ten primary food flavonoids in both conventional solvents and natural deep eutectic solvents (NADES), utilizing five choline chloride-based NADES. These NADES were formulated with lactic acid, ascorbic acid, urea, sorbitol, and 1,2-propanediol as hydrogen bond donors (HBD). Conventional solvents used in the comparison included water, menthol, and ethanol. The flavonoids studied—catechin, daidzein, quercetin, naringenin, luteolin, genistein, kaempferol, apigenin, diosmetin, and chrysin—were analyzed for solubility and extractability via both solvents. Flavonoid solubility was observed to vary based on both the structural characteristics of the flavonoid and the choice of HBD. Notably, catechin demonstrated the highest solubility across all solvent systems, followed by naringenin and quercetin. Among the NADES systems, the blend based on 1,2-propanediol notably enhanced the solubility of quercetin and luteolin to 53.4 mg/mL and 26.9 mg/mL, respectively, surpassing their solubility in conventional solvents. The empirical findings were consistent with theoretical predictions made using the COSMO-RS method, confirming the efficacy of NADES in solubilizing food flavonoids more effectively than conventional solvents.

Multienzymatic biotransformation of flavokawain B by entomopathogenic filamentous fungi: structural modifications and pharmacological predictions

BackgroundFlavokawain B is one of the naturally occurring chalcones in the kava plant (Piper methysticum). It exhibits anticancer, anti-inflammatory and antimalarial properties. Due to its therapeutic potential, flavokawain B holds promise for the treatment of many diseases. However, due to its poor bioavailability and low aqueous solubility, its application remains limited. The attachment of a sugar unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Biotransformation is an environmentally friendly way to improve the properties of compounds, for example, to increase their hydrophilicity and thus affect their bioavailability. Recent studies proved that entomopathogenic filamentous fungi from the genera Isaria and Beauveria can perform O-methylglycosylation of hydroxyflavonoids or O-demethylation and hydroxylation of selected chalcones and flavones.ResultsIn the present study, we examined the ability of entomopathogenic filamentous fungal strains of Beauveria bassiana, Beauveria caledonica, Isaria farinosa, Isaria fumosorosea, and Isaria tenuipes to transform flavokawain B into its glycosylated derivatives. The main process occurring during the reaction is O-demethylation and/or hydroxylation followed by 4-O-methylglycosylation. The substrate used was characterized by low susceptibility to transformations compared to our previously described transformations of flavones and chalcones in the cultures of the tested strains. However, in the culture of the B. bassiana KCh J1.5 and BBT, Metarhizium robertsii MU4, and I. tenuipes MU35, the expected methylglycosides were obtained with high yields. Cheminformatic analyses indicated altered physicochemical and pharmacokinetic properties in the derivatives compared to flavokawain B. Pharmacological predictions suggested potential anticarcinogenic activity, caspase 3 stimulation, and antileishmanial effects.ConclusionsIn summary, the study provided valuable insights into the enzymatic transformations of flavokawain B by entomopathogenic filamentous fungi, elucidating the structural modifications and predicting potential pharmacological activities of the obtained derivatives. The findings contribute to the understanding of the biocatalytic capabilities of these microbial cultures and the potential therapeutic applications of the modified flavokawain B derivatives.

Glycosylation of Quercetin by Selected Entomopathogenic Filamentous Fungi and Prediction of Its Products' Bioactivity.

Quercetin is the most abundant flavonoid in food products, including berries, apples, cauliflower, tea, cabbage, nuts, onions, red wine and fruit juices. It exhibits various biological activities and is used for medical applications, such as treating allergic, inflammatory and metabolic disorders, ophthalmic and cardiovascular diseases, and arthritis. However, its low water solubility may limit quercetin's therapeutic potential. One method of increasing the solubility of active compounds is their coupling to polar molecules, such as sugars. The attachment of a glucose unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Entomopathogenic fungi are biocatalysts well known for their ability to attach glucose and its 4-O-methyl derivative to bioactive compounds, including flavonoids. We investigated the ability of cultures of entomopathogenic fungi belonging to Beauveria, Isaria, Metapochonia, Lecanicillium and Metarhizium genera to biotransform quercetin. Three major glycosylation products were detected: (1), 7-O-β-D-(4″-O-methylglucopyranosyl)-quercetin, (2) 3-O-β-D-(4″-O-methylglucopyranosyl)-quercetin and (3) 3-O-β-D-(glucopyranosyl)-quercetin. The results show evident variability of the biotransformation process, both between strains of the tested biocatalysts from different species and between strains of the same species. Pharmacokinetic and pharmacodynamic properties of the obtained compounds were predicted with the use of cheminformatics tools. The study showed that the obtained compounds may have applications as effective modulators of intestinal flora and may be stronger hepato-, cardio- and vasoprotectants and free radical scavengers than quercetin.

Morin Hydrate Encapsulation and Release from Mesoporous Silica Nanoparticles for Melanoma Therapy.

Melanoma incidence, a type of skin cancer, has been increasing worldwide. There is a strong need to develop new therapeutic strategies to improve melanoma treatment. Morin is a bioflavonoid with the potential for use in the treatment of cancer, including melanoma. However, therapeutic applications of morin are restrained owing to its low aqueous solubility and limited bioavailability. This work investigates morin hydrate (MH) encapsulation in mesoporous silica nanoparticles (MSNs) to enhance morin bioavailability and consequently increase the antitumor effects in melanoma cells. Spheroidal MSNs with a mean size of 56.3 ± 6.5 nm and a specific surface area of 816 m2/g were synthesized. MH was successfully loaded (MH-MSN) using the evaporation method, with a loading capacity of 28.3% and loading efficiency of 99.1%. In vitro release studies showed that morin release from MH-MSNs was enhanced at pH 5.2, indicating increased flavonoid solubility. The in vitro cytotoxicity of MH and MH-MSNs on human A375, MNT-1 and SK-MEL-28 melanoma cell lines was investigated. Exposure to MSNs did not affect the cell viability of any of the cell lines tested, suggesting that the nanoparticles are biocompatible. The effect of MH and MH-MSNs on reducing cell viability was time- and concentration-dependent in all melanoma cell lines. The A375 and SK-MEL-28 cell lines were slightly more sensitive than MNT-1 cells in both the MH and MH-MSN treatments. Our findings suggest that MH-MSNs are a promising delivery system for the treatment of melanoma.

Insight into the Glycosylation Methods of the Flavonoids as an Approach to Enhance its Bioavailability and Pharmacological Activities

Abstract: Background: Flavonoids are a kind of polyphenol having a diverse set of pharmacological applications, but their bioavailability is limited due to their poor stability, poor solubility, quick clearance, and low intrinsic characteristics. According to the prior study, the flavonoids containing the sugar moiety have better solubility and stability (for example rutin) as they maintain greater plasma levels and a longer mean residence duration than the flavonoids have no glycoside moiety. Aim: This review focus on the enhancement of solubility and bioavailability of flavonoids by the various glycosylation techniques. Materials and Methods: In this review study, we discussed the various glycosylation approaches to improve solubility and bioavailability, such as microbial biotransformation, enzyme pathway manipulation, metabolic engineering, and chemical synthesis. Results: Glycosylation is one of the most efficient methods for increasing flavonoid solubility and stability, as a result the pharmacological activity also enhanced. The glycosylated compound such as scutellarin, quercetin 3-O-glucoside, Cyanidin 3-O-glucoside, kaempferitrin, baicalein 7-O-glucuronide and so on, shows the increased solubility and better pharmacological activities. Conclusion: The flavonoids need more attention to overcome their limitations, as they have plethora of applications on human health such as free radical scavenging property, anti-cancer activity, anti-diabetic, anti-inflammatory. Keywords: Flavonoids, Classification, Limitations, Bioavailability, Glycosylation.

The Effect of Lactic Acid Fermentation on Extraction of Phenolics and Flavonoids from Sage Leaves

This work analysed the effect of spontaneous fermentation of sage leaves on the release and extraction of flavonoid and phenolic compounds. Chemical profiling based on thin-layer chromatography was used to compare different extracts from two sage species, common sage (Salvia officinalis) and white sage (Salvia apiana). Non-fermented Salvia apiana extracts are richer in antioxidants, phenolics, and terpenoids. Fermentation significantly enhances extraction of total phenolics, flavonoids, and antioxidants only from Salvia officinalis leaves, while it does not affect extraction from Salvia apiana leaves. In each 20 µL of extract, extraction of polyphenolics increases from 6.55 to 21.01 µg gallic acid equivalents (GAE), anti-oxidants from 0.68 to 2.12 µg GAE, and flavonoid content from 48.01 to 65.33 µg RE (rutin equivalents). Higher antioxidant activity in fermented Salvia apiana ethyl acetate extracts is associated with an increased concentration of phenolics and phenolic terpenoids. However, in Salvia officinalis, the higher antioxidant activity of fermented extract is a result of the release and improved extraction of flavonoids, as there is no increase in the extraction of phenolics. Lactic acid produced via fermentation and proline from Salvia officinalis leaves forms a natural deep eutectic solvent (NADES), which significantly increases the solubility of flavonoids.

Bioinformatics-Guided Identification of Ethyl Acetate Extract of Citri Reticulatae Pericarpium as a Functional Food Ingredient with Anti-Inflammatory Potential.

Citri Reticulatae Pericarpium (CRP) is one of the most commonly used food supplements and folk medicines worldwide, and possesses cardiovascular, digestive, and respiratory protective effects partially through its antioxidant and anti-inflammatory functions. The unique aromatic flavor and mild side effects make CRP a promising candidate for the development of anti-inflammatory functional food. However, recent studies show that the crude alcoholic extract and some isolated compounds of CRP show compromised anti-inflammatory activity, which became the main factor hindering its further development. To identify the bioactive compounds with anti-inflammatory potential, and improve the anti-inflammatory effects of the extract, a bioinformatics-guided extraction protocol was employed in this study. The potential bioactive candidates were identified by combing network pharmacology analysis, molecular docking, principal components analysis, k-means clustering, and in vitro testing of reference compounds. Our results demonstrated that 66 compounds in CRP could be grouped into four clusters according to their docking score profile against 24 receptors, while the cluster containing flavonoids and phenols might possess a more promising anti-inflammatory function. In addition, in vitro anti-inflammatory tests of the seven reference compounds demonstrated that hesperitin, naringenin, and gardenin B, which were grouped into a cluster containing flavonoids and phenols, significantly decreased LPS-induced NO, TNF-α, and IL-6 production of macrophages. While the compounds outside of that cluster, such as neohesperidin, naringin, hesperidin, and sinensetin showed little effect on alleviating LPS-induced NO and proinflammatory cytokine production. Based on the chemical properties of selected compounds, ethyl acetate (EtOAc) was selected as the solvent for extraction, because of its promising solubility of flavonoids and phenols. Furthermore, the ethanol alcoholic extract was used as a reference. The chemical profiling of EtOAc and crude alcoholic extract by HPLC/MS/MS also demonstrated the decreased abundance of flavonoid glycosides in EtOAc extract but increased abundance of phenols, phenolic acid, and aglycones. In accordance with the prediction, the EtOAc extract of CRP, but not the crude alcoholic extract, significantly decreased the NO, IL-6, and TNF-α production. Taken together, the results suggested selective extraction of phenols and flavonoids rich extract was able to increase the anti-inflammatory potential of CRP partially because of the synergistic effects between flavonoids, phenols, and enriched polymethoxyflavones. Our study might pave the road for the development of ethyl acetate extract of CRP as a novel functional food with anti-inflammatory function.

Enzymatic glucosylation of citrus flavonoids to enhance their bioactivity and taste as new food additives

Cyclodextrin glucosyltransferase (CGTase) is commonly used to produce cyclodextrins but its utility in flavonoids modification is rarely found. In the present study, an enzymatic transformation of citrus flavonoids by applying CGTase as the catalyst was investigated to produce a number of novel polyglucosylated derivatives from monoglucoside metabolites of citrus flavonoid diglycosides. Under the optimized conditions, the yield of glucosylated products achieved 80%. The water solubility and water partition coefficient of citrus flavonoids before and after the structural modification were compared. The results revealed that the water solubility of the flavonoids modified by glucosylation was significantly increased while the oil-water partition coefficient was just slightly reduced. Moreover, after glucosylation, the products have good anti-inflammatory and antioxidant effects. Interestingly, the taste property (bitterness and sweetness) of the glucosylated products was ameliorated. An evaluation with a Taste-Sensing System showed that the taste of the glucosylated products was strongly correlated with the attached rhamnosyl group (bitter taste) and glucosyl group (sweet taste), indicating that the amelioration of taste of flavonoids could be mainly attributed to the addition of glycosyl groups. The present study demonstrated a novel molecular engineering approach for the enhancement of water solubility and amelioration of taste for some citrus flavonoids, which may have potential applications in the functional food industry.

Fisetin glycosides synthesized by cyclodextrin glycosyltransferase from Paenibacillus sp. RB01: characterization, molecular docking, and antioxidant activity.

Fisetin is a flavonoid that exhibits high antioxidant activity and is widely employed in the pharmacological industries. However, the application of fisetin is limited due to its low water solubility. In this study, glycoside derivatives of fisetin were synthesized by an enzymatic reaction using cyclodextrin glycosyltransferase (CGTase) from Paenibacillus sp. RB01 in order to improve the water solubility of fisetin. Under optimal conditions, CGTase was able to convert more than 400 mg/L of fisetin to its glycoside derivatives, which is significantly higher than the previous biosynthesis using engineered E. coli. Product characterization by HPLC and LC-MS/MS revealed that the transglycosylated products consisted of at least five fisetin glycoside derivatives, including fisetin mono-, di- and triglucosides, as well as their isomers. Enzymatic analysis by glucoamylase and α-glucosidase showed that these fisetin glycosides were formed by α-1,4-glycosidic linkages. Molecular docking demonstrated that there are two possible binding modes of fisetin in the enzyme active site containing CGTase-glysosyl intermediate, in which O7 and O4’ atoms of fisetin positioned close to the C1 of glycoside donor, corresponding to the isomers of the obtained fisetin monoglucosides. In addition, the water solubility and the antioxidant activity of the fisetin monoglucosides were tested. It was found that their water solubility was increased at least 800 times when compared to that of their parent molecule while still maintaining the antioxidant activity. This study revealed the potential application of CGTase to improve the solubility of flavonoids.

Investigation of phenolic, flavonoid, and antioxidant recovery and solubility from Roselle using supercritical carbon dioxide: Experiment and modeling

The purpose of this work was to determine the optimal conditions for recovering high yields of total phenolic compounds (TPC), total flavonoid compounds (TFC), and antioxidant activity (AA) from roselle (Hibiscus sabdariffa) by employing supercritical carbon dioxide (ScCO2). The solubility of yield, phenolic, and flavonoid in ScCO2 was estimated using solubility models. Pressure (10 to 20 MPa), temperature (40 to 60°C), and flow rate (3 to 5 ml/min) were used as factors in this investigation. According to the response surface methodology (RSM), the optimal conditions were 20 MPa, 40°C, and 4.875 ml/min, yielding 14.11%, 935.48 mgGAE/L TPC, 812.16 mgQUE/L TFC, and 98.59% antioxidant activity, respectively. With 5.29%, 1.28%, and 1.34% of average absolute relative deviation (AARD), the Putra model provided the best connection to the yield extract, phenolic, and flavonoid solubility. The use of RSM and modeling was effective in attaining a high production and concentration of phenolic compounds. Practical applications Roselle (Hibiscus sabdariffa) comprises several beneficial components, including phenolic, flavonoid, and antioxidant substances. It is used to treat pyrexia, liver damage, hypertension, and leukemia, among other conditions. Toxic and conventional solvents, on the other hand, have often been utilized to recover these valuable compounds. To alleviate these disadvantages, the important chemicals in roselle are extracted using supercritical carbon dioxide (ScCO2). The solubility behavior of oil yield, phenolic, and flavonoid compounds was determined in this work using a semi-empirical model. The data indicate that an endothermic process occurred to enhance the solubility of yield extract and the exothermic process is suitable for the phenolic and flavonoid recovery.

A multi-targeted approach to identify potential flavonoids against three targets in the SARS-CoV-2 life cycle

The advent and persistence of the Severe Acute Respiratory Syndrome Coronavirus – 2 (SARS-CoV-2)-induced Coronavirus Disease (COVID-19) pandemic since December 2019 has created the largest public health emergency in over a century. Despite the administration of multiple vaccines across the globe, there continues to be a lack of approved efficacious non-prophylactic interventions for the disease. Flavonoids are a class of phytochemicals with historically established antiviral, anti-inflammatory and antioxidative properties that are effective against cancers, type 2 diabetes mellitus, and even other human coronaviruses. To identify the most promising bioactive flavonoids against the SARS-CoV-2, this article screened a virtual library of 46 bioactive flavonoids against three promising targets in the SARS-CoV-2 life cycle: human TMPRSS2 protein, 3CLpro, and PLpro. By examining the effects of glycosylation and other structural-activity relationships, the presence of sugar moiety in flavonoids significantly reduces its binding energy. It increases the solubility of flavonoids leading to reduced toxicity and higher bioavailability. Through protein-ligand contact profiling, it was concluded that naringin formed more hydrogen bonds with TMPRSS2 and 3CLpro.In contrast, hesperidin formed a more significant number of hydrogen bonds with PLpro. These observations were complimented by the 100 ns molecular dynamics simulation and binding free energy analysis, which showed a considerable stability of docked bioflavonoids in the active site of SARS-CoV-2 target proteins. Finally, the binding affinity and stability of the selected docked complexes were compared with the reference ligands (camostat for TMPRSS2, GC376 for 3CLpro, and GRL0617 for PLpro) that strongly inhibit their respective SARS-COV-2 targets. Overall analysis revealed that the selected flavonoids could be potential therapeutic agents against SARS-CoV-2. Naringin showed better affinity and stability for TMPRSS2 and 3CLpro, whereas hesperidin showed a better binding relationship and stability for PLpro.

Mesoporous SBA-15 Silica-Loaded Nano-formulation of Quercetin: A Probable Radio-Sensitizer for Lung Carcinoma.

Lung cancer is considered as one of the most serious disease worldwide. The progress of drug carriers based on nonmaterial, which selectively hold chemotherapeutic agents to cancer cells, has become a major focus in biomedical research. This study aimed to evaluate the growth inhibition and apoptosis induction of the human lung cancer cells (A-549) by Q-loaded SBA-15 conjugate system. Mesoporous silica nanoparticles (SBA-15) as host materials for transporting therapeutics medicaments were fabricated for targeted drug delivery toward lung cancer. With the objective of increasing bioavailability and aqueous solubility of flavonoids, SBA-15 was successfully loaded with the quercetin (Q)—a major flavonoid and characterized with the help of Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The biological investigation on A549 cell line confirmed that the efficacy of Q-SBA-15 is much higher than only Q. Moreover, the apoptotic pathway of synthesized Q-SBA-15 NPs examined that the Q-SBA-15–mediated apoptosis via PI3K/AKT/mTOR signaling pathway. Thus, the newly conjugated Q-SBA-15 system improved the apoptotic fate through caspase-mediated apoptosis via PI3K/AKT/mTOR signaling pathway and hence, it can be potentially employed as an anticancer agent for lung cancer.

Thermodynamic and structural description of relative solubility of the flavonoid rutin by DFT calculations and molecular dynamics simulations

Understanding the solubility of flavonoids is of relevance in view of the broad application such as antioxidant and antitumor agents. The solubility of flavonoid rutin has been experimentally investigated in a homologous series of alcohols, acetone, n-heptane and water solvents. In this work theoretical evaluation of Gibbs free energy of solvation was performed at the Density Functional Theory (DFT) and Molecular Dynamics (MD) levels, with the ωB97x-D functional and multistate Bennett acceptance ratio (MBAR) method, respectively. The degree of solubility of a given solute among various solvents is dictated by solute-solvent interactions, which may be represented by the solvation energy. Our calculated relative energy values due to solvent effects, using quantum chemical methods (PCM and SMD solvent models) do not follow strictly the observed solubility trend. However, the PCM model including solute-solvent dispersion interaction, solute-solvent repulsion interaction and solute cavitation energy contribution to the total energy (named DIS,REP,CAV) yielded an overall agreement with experimental solubility profile, with exception of ethanol solvent. A similar satisfactory accordance with experiment was found for MBresults, with a discrepancy also found for 1-butanol, which deserve further investigation. Analysis of spatial and radial distribution functions (SDF and RDF) for pure solvents and the analysis of the contributions of vdW and electrostatic terms for the total free energy reveal that a balance between dispersive and electrostatic interactions between the rutin and the solvent is necessary to solubilize the flavonoid, which corroborates with the values of these energy contributions to the solvation-free energy calculated by the MBAR method. The use of explicit solvent molecules in DFT calculations is precluded due to the size, flexibility, and many sites for solvent interactions of rutin molecule. Our results indicate that in general DFT-PCM (DIS,REP,CAV) and MBAR levels of calculations can satisfactorily predict the solvation free energy and solubility trend for flavonoid rutin along a series of solvents, and also provide a reasonable estimate of relative solubilities of other flavonoids, information that can be relevant for further molecular modeling studies.

Використання полімерних композиційних матеріалів для підвищення біодоступності гесперидина

Purpose. Investigation of the influence of the composition of polymeric solubilizers on the phase solubilization in water of the model active pharmaceutical ingredient of flavonoid nature hesperidin.Methods. Hesperidin was chosen as a model substance of characteristic chemical structure. Pharmaceutically acceptable high molecular weight polymers based on polyvinylpyrrolidone (PVP) with a molecular weight of from 2500 to 58000 D were used for research; cetylpyridinium chloride; β-cyclodextrin. Phase solubilization of hesperidin was investigated by the method of Higuchi and Connors. The concentration of hesperidin was determined spectrophotometrically by absorption at 284 nm. The phase solubility diagram was constructed as the dependence of the concentration of hesperidin in solution on the concentration of the polymer. The obtained phase solubility profiles of hesperidin were compared with standard curves. For different compositions at the experiment temperature of 37 ± 0.5 °C, the stability constant and the dissociation constant of intermolecular complexes were calculated.Scientific novelty. The influence of the composition of polymer solubilizers on the phase solubilization in water of the model API of flavonoid nature of hesperidin was established. Practical significance. The optimal composition of the polymer composite material with hesperidin in the form of a solid dispersed system to maximize the solubility of flavonoids in water is substantiated. Results. The influence of the composition of polymer solubilizers on the phase solubilization in water of the model API of flavonoid nature of hesperidin was investigated. Based on the results of graphical analysis of the obtained data, it was concluded that the solubility of hesperidin increases with increasing number of polymers with different molecular weights and surfactants. The increase in solubility depends on the composition. When adding several polymers or a combination of a polymer with a surfactant, the solubility increases significantly more than when adding one compound. It is shown that the maximum value of solubility increase is observed in the system with polymer C and K surfactant - 42.7 times. It was found that the stability constants of polymeric composite materials of hesperidin based on polyvinylpyrrolidones are in the range from 161.87 to 219.88 M-1, which indicates favorable conditions for the formation of complexes.

Encapsulation Systems for Delivery of Flavonoids: A Review

Encapsulation of bioactive compounds s been considered a promising tool for preserving these compounds. Several studies on dietary sources and health benefits of flavonoids, their chemical and stability properties, and encapsulation methods used for delivery of flavonoids were reviewed. Flavonoids comprise the main group of polyphenols widely found in fruits and vegetables responsible for numerous biological activities. They have a flavan nucleus with 15 carbon atoms organized in three rings and are categorized into six subgroups. The main dietary sources of flavonoids are fruits, vegetables, cereals, tea, and some herbs such as Viola odorata Linn. These compounds can prevent diseases such as cardiovascular, cancers, neurodegenerative, diabetes, and inflammatory bowel disease. Despite these beneficial biological activities, flavonoids are not stable against environmental conditions, have low water solubility and low bioavailability after oral administration, which restricts their application. Accordingly, encapsulation has been utilized in order to improve the stability and solubility of flavonoids. Various approaches such as spray drying, molecular complexes, liposomes, nanoparticles, emulsification, and multilamellar vesicles have been applied in the entrapment of flavonoids. Encapsulation can improve the stability of flavonoids as well as solubility, controlled release, and bioavailability.

Study on Solubilization and Stabilization of Eight Flavonoids by 17 Chinese Herbal Polysaccharides

Flavonoids are important active components of traditional Chinese medicines (TCMs) because of their many biological activities. We studied the interaction between 17 polysaccharides and eight flavonoids via high-performance liquid chromatography (HPLC) and the effect of the interactions on the solubility and stability of the flavonoids. The effect of the polysaccharides on the solubility of flavonoids was analyzed by statistical methods and showed significant solubility improvements. The constant temperature acceleration method (90°C/pH 9 buffer solution) was used to measure the degradation kinetics and half-life of flavonoids with and without polysaccharides. All the polysaccharides displayed a stabilizing effect on all eight flavonoids. The stabilizing effects varied in the order: quercetin, baicalein > baicalin > galuteolin > daidzin > rutin > luteolin > daidzien. The phase-solubility method was applied to quercetin and baicalein to study the mechanism of action of the polysaccharides. It appeared that the two flavonoids could form 1 : 1 inclusion complexes with polysaccharides, which may be one of the factors increasing solubility and stability. These findings increase our understanding of the role of endogenous polysaccharides in TCM in improving the stability and bioavailability of bioactive flavonoids.

Identification and characterization of three flavonoid 3-O-glycosyltransferases from Epimedium koreanum Nakai

Glycosylation of flavonoids is one of the most important modifications in flavonoid biosynthesis pathways, which contributes to the biochemical activity as well as the solubility of flavonoids. However, reports on glycosyltransferases that catalyze specifically the 3-O-glycosylation of flavonoids are limited. In the current work, three novel flavonoid 3-O-glycosyltransferases as well as one UDP-rhamnose synthase were identified and functionally characterized using RNA sequencing from Epimedium koreanum Nakai. These glycosyltransferases were found to catalyze the glucosylation, galactosylation and rhamnosylation of several flavonoids specifically at the 3-OH position. Phylogenetic analysis of the three glycosyltransferases showed that they all belonged to the 3 G T family. According to the results, the three newly identified glycosyltransferases from Epimedium exhibited glycosylation activity especially toward prenylated flavonoids which has never been reported before. The bioconversion experiment with engineered yeasts expressing the three glycosyltransferases showed great application potential in glycosylation of flavonoids. All these studies contributed to a better understanding of flavonoid 3-O-glycosyltransferases from Epimedium and will promote the biosynthesis of different kinds of bioactive flavonoid glycosides with synthetic biology methods.

Recovery and solubility of flavonoid and phenolic contents from Arachis Hypogea in supercritical carbon dioxide assisted by ethanol as cosolvent

Supercritical carbon dioxide (ScCO2) extraction assisted by Ethanol is one of the development methods to extract polar and nonpolar compounds. Thus, the objective of the study was to optimize extraction parameters to recover total phenolic content (TPC) and total flavonoid content (TFC) from peanut skin. Chrastil, Del Valle Aguilera, and Adachi-Lu models were applied to determine the solubility behaviors. The optimum condition was found at 29.43 MPa, 319.16 K, and 0.09 ml/min with 290.12 mg/L TPC and 488.26 mg/L TFC. Chrastil model gives good agreement to fit the solubility of flavonoid and phenolic contents due to the lowest Average absolute relative deviation were 3.27% and 7.75%, respectively. Practical applications Peanut skin as waste of peanut industries contains high phenolic and flavonoid contents. Currently, conventional extraction process with toxic solvent has been used to extract peanut skin. ScCO2extraction is one of the solutions to break the limitation of solvent's toxicity. However, ScCO2 has the drawbacks that ScCO2 is powerful to extract the nonpolar compounds, but failure to extract the medium polar compounds especially for the flavonoid compounds. Thus, the addition of ethanol is one of development method to break this limitation. Furthermore, Semi-empirical model has been used in this study to determine the solubility behavior to enhance the solubility of phenolic and flavonoid contents. The results show that high temperature condition is suitable to enhance the solubility of TPC, otherwise low temperature condition is preferable in the enhancement of TFC solubility.

A Novel and High-Effective Biosynthesis Pathway of Hesperetin-7-O-Glucoside Based on the Construction of Immobilized Rhamnosidase Reaction Platform.

Hesperetin-7-O-glucoside (HMG) is a precursor for synthesizing a sweetener named neohesperidin dihydrochalcone, and the coordination toward flavonoids of metal ions tends to increase the water solubility of flavonoids. In order to achieve effective synthesis of HMG, an immobilized enzyme catalysis platform was constructed using an immobilized rhamnosidase on Fe3O4@graphene oxide (Fe3O4@GO), a novel reaction pathway based on the platform was designed for preparing a hesperidin complex as a soluble substrate, and ammonium hydroxide as a ligand dissociation agent to obtain HMG. The Fe3O4@GO was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal methods (TG/DSC) analysis to evaluate the immobilization matrix properties. The enzyme activity in free and immobilized form at different pH and temperature was optimized. The reusability of immobilized enzyme was also determined. In addition, the kinetic parameters (Km and Vmax) were computed after experiment. Results indicated that rhamnosidase immobilized on Fe3O4@GO using a green cross-linker of genipin hydrolyzed successfully and selectively the soluble hesperidin-Cu (II) complex into HMG-Cu (II), a permanent magnet helped the separation of immobilized enzyme and hydrolytes, and ammonium hydroxide was an effective ligand dissociation agent of translating HMG-Cu (II) into HMG with high purity determined by ultraviolet-visible (UV-Vis) spectra analysis and time-of-flight mass spectrometry (TOF-MS). As a result, a novel and high-effective biosynthesis pathway of HMG based on a selectively catalytic reaction platform were constructed successfully. The pathway based on the platform has great potential to produce valuable citrus monoglycoside flavonoid HMG, and the designed reaction route are feasible using the hesperidin-Cu (II) complex with good solubility as a reaction substrate and using ammonium water as a dissociation agent.

Effects of Astragalus polysaccharide on the solubility and stability of 15 flavonoids

Poor solubility and stability are limitation factors of flavonoids application. Polysaccharides from herbs have been proven to be functional foods and potential promising natural supplements with large molecular weight and complex structures. Astragalus polysaccharides (APS) are the main components of Astragalus membranaceus (Fisch.) and novel synergistic pharmacological effects between Astragalus polysaccharides and flavonoids have been reported. However, the general effects of polysaccharides when co-administered with flavonoids are currently unknown. Herein, the influences of APS on aqueous solubilities and stabilities of fifteen flavonoids were systematically investigated, and the mechanism of effects of polysaccharides on flavonoids was further considered. The results showed that APS could significantly enhance the solubilities and stabilities of the flavonoids, with solubilization effect improved by 68.88-fold for quercetin and negatively correlated with the aqueous solubility of the flavonoid itself. A phase solubility study and Differential scanning calorimetry characterization indicated that APS could form complexes with flavonoids at 1:1 ratio with K values ranging from 1491 to 55,395 L·mol−1, a tendency to improved solubilization at higher association constant values was also observed. Those findings could provide the basis for a new approach to solving the problems of poor solubility and stability of flavonoids through the application of natural macromolecules.