Hydrophobic Quercetin Research Articles

O1/W/O2 double emulsion gels based on nanoemulsions and Pickering particles for co-encapsulating quercetin and cyanidin: A functional fat substitute

An O1/W/O2 double emulsion gel, as a functional fat substitute and based on nanoemulsions and hydrophobic Pickering particles, is prepared by two-step emulsification to co-encapsulate hydrophilic cyanidin and hydrophobic quercetin. Nanoemulsions loading quercetin are fabricated by Tween-80 and combining high-speed and high-pressure emulsification. Phytosterol nanoparticles stabilize the W-O2 interface of the secondary emulsion to load cyanidin in the W phase. The concentration of Tween-80 is optimized as 0.3% by the droplet size and viscosity of nanoemulsions. The structural stability of double emulsion gels will be weakened along with the increase of nanoemulsions, showing lower modulus and encapsulation efficiency (EE) and bigger droplets. In double emulsion gels, the EE of quercetin and cyanidin reaches 93% and 85.6%, respectively. Analysis of molecular interaction indicates that Tween-80 would decrease the in-situ hydrophobicity of phytosterol nanoparticles by hydrogen bonding adsorption, thereby weakening the emulsification. The pH-chromic 3D printing of double emulsion gels is designed according to the pH sensitivity of cyanidin. Texture profile analysis is performed to test the textural properties of 3D-printed objects. The simulated digestion is conducted on double emulsion gels. The double emulsion gel with fewer nanoemulsions is beneficial for protecting quercetin and improving the delivery due to the higher structural stability, while that with more nanoemulsions is conducive to the digestion of cyanidin and camellia oil due to weakened semi-solid properties. This double emulsion gel further simulates fat tissues by co-encapsulating hydrophilic and hydrophobic substances, promoting the application of fat substitutes in the food industry.

Green-step assembly of the supramolecular amphiphile constructed by sodium carboxymethyl cellulose and calixarene for facile loading of hydrophobic food bioactive compounds.

The use of biologically active compounds is often limited due to their poor aqueous solubility, which generally reduces their bioavailability and useful efficacy. In this regard, a wide search is currently underway for colloidal systems capable of encapsulating these compounds. In the creation of colloidal systems, long-chain molecules of surfactants and polymers are mainly used, which in an individual state do not always aggregate into homogeneous and stable nanoparticles. In the present work, cavity-bearing calixarene was used for the first time to order polymeric molecules of sodium carboxymethyl cellulose. A set of physicochemical methods demonstrated the spontaneous formation of spherical nanoparticles by non-covalent self-assembly contributed by macrocycle and polymer, and formed nanoparticles were able to encapsulate hydrophobic quercetin and oleic acid. The preparation of nanoparticles by supramolecular self-assembly without use of organic solvents, temperature and ultrasound effects can be an effective strategy for creating water-soluble forms of lipophilic bioactive compounds.

Doxorubicin and Quercetin Double Loading in Modified MCM-41 Lowered Cardiotoxicity in H9c2 Cardioblast Cells In Vitro.

One of the therapeutic limitations of the use of doxorubicin (DOX) as an anticancer drug is its cardiotoxicity. Its hydrophilicity also causes difficulties in achieving sustained release. The simultaneous delivery with the well-known natural antioxidant quercetin could ameliorate its cardiotoxicity. Thus, the main aim of this work is to study the potential of carboxylated and non-carboxylated mesoporous silica MCM-41 nanoparticles for double loading of the hydrophilic doxorubicin hydrochloride and hydrophobic quercetin (Q) in one nanocarrier with a modified release pattern to reduce the cardiotoxic side effects of doxorubicin in vitro. The methods included the modification of MCM-41, single and double loading of modified and non-modified MCM-41, physicochemical characterization, in vitro release tests and kinetic study, and in vitro cell viability studies. Doxorubicin and quercetin were successfully double-loaded with encapsulation efficiency (EE) of 43 ± 4.1% and 37 ± 4.5%, respectively, in native MCM-41. The post-synthetic carboxylation led to 49 ± 4.3% EE (DOX) and 36 ± 4.0% (Q) and double lowering of the cardiotoxicity on H9c2 (IC50 = 5.96 µm). Sustained release profiles over 72 h were achieved. A successful procedure was proposed for the efficient double loading of a hydrophilic drug and a hydrophobic drug. The carboxy-modified double-loaded nanosystems demonstrate a decreased in vitro cardiotoxicity of doxorubicin and can be considered as a potential chemotherapeutic formulation.

Pectin / chitosan nanoparticle beads as potential carriers for quercetin release

The present work explores the fabrication of pectin/chitosan nanoparticle (PEC/CSNP) beads as nanocarrier encapsulating hydrophobic quercetin overcome solubility and sensitivity problems by ionotropic gelation method. ATR-FTIR studies evidenced the chemical interaction among the drug and the polymer matrix. The surface morphology of the unloaded and quercetin loaded PEC/CSNPs beads were characterized by scanning electron microscopy. The nanoparticulate beads had higher % encapsulation efficiency (EE) that varied between 34% and 56.2% and loading capacity (LC) from 12% to 24.4%. In vitro drug release study of the beads showed a capacity to release quercetin in a sustained release pattern. The swelling behavior of the beads demonstrated an increase in mechanical resistance due to the presence of pectin in the formulation at low pH. The association of quercetin and the polymeric nanoparticles induces a synergistic effect that improved the beads antibacterial properties. The antioxidant potency of quercetin was enhanced by 71% after encapsulation and hemolysis studies showed good blood compatibility. The in vitro cytotoxicity of blank and Q-PEC/CSNP beads showed cell viability above 80% on the L929 cell line. These results suggested that the PEC/CSNPs beads can be suitably an effective drug delivery vehicle emphasizing the stability of chitosan nanoparticles in the gastrointestinal tract where pH is low.

Amphiphilic nano-delivery system based on modified-chitosan and ovalbumin: Delivery and stability in simulated digestion

Nano-delivery systems play an important role in the development of nutritional supplements due to their efficient encapsulation and delivery properties for nutrients. Herein, we prepared protein-polysaccharide nanoparticles as a novel amphiphilic nano-delivery system based on gallic acid modified chitosan (GCS) and ovalbumin (OVA) by pH-driven and calcium ion crosslinking. The nanoparticles loaded with hydrophilic riboflavin (Rib) and hydrophobic quercetin (Que) as nutrient models were abbreviated as GCS-OVA-Rib NPs and GCS-OVA-Que NPs, respectively. Their encapsulation efficiencies for Rib and Que. were 66.36 % and 96.61 %, respectively. In addition, GCS-OVA-Rib NPs and GCS-OVA-Que NPs showed antioxidant activity as well as good stability and delivery capacity for Rib and Que. in simulated digestion with release ratios of 78.38 % and 84.15 %, respectively. More importantly, GCS-OVA-Rib/Que. NPs performed good biocompatibility for further applications. Overall, this work provides some useful insights for the design of novel amphiphilic nano-delivery systems based on polysaccharides and proteins.

Highly specific β‑glucuronidase light-up natural fluorescent probe with aggregation-induced emission and excited-state intramolecular proton transfer for inhibitors screening and in situ imaging in Escherichia coli

Expression of β-glucuronidase (GUS) in intestinal bacteria has attracted more and more attentions because of its relevant to drug-inducing enteropathy and enterohepatic circulation. Hence it is essential to develop a facile method for efficient inhibitors screening and in situ activity tracking of GUS. Here, a novel light-up natural fluorescent probe, quercetin-3-O-β-D-glucuronide (obtained from Bupleurum scorzonerifolium), for rapid, sensitive, and specific analysis of GUS activity was found. Hydrophilic quercetin-3-O-β-D-glucuronide was catalyzed by GUS to produce hydrophobic quercetin aggregates in situ. The occurrence of quercetin fluorescence at 540 nm (Stokes shift = 175 nm) with aggregation-induced emission and excited-state intramolecular proton transfer characteristics was light-up, which can be used to evaluate GUS activity. A good linear range (5.0–60.0 μg mL−1, R2 = 0.9904), high sensitivity (limit of detection at 0.7 μg mL−1), satisfying precision (relative standard deviation values at 1.2% and 3.0% for intra-day and inter-day variations) and superior selectivity to GUS were obtained. Then, a facile platform for screening of GUS inhibitors from natural compounds library was constructed successfully. Three natural compounds, resveratrol (IC50 = 0.45 ± 0.04 μM), hesperidin (IC50 = 1.46 ± 0.07 μM), and ursolic acid (IC50 = 7.85 ± 0.26 μM)) were screened out with stronger inhibitory efficiency. Furthermore, on account of the outstanding photostability and excellent biocompatibility, quercetin-3-O-β-D-glucuronide has been employed for in situ imaging of endogenous GUS in Escherichia coli noninvasively with low background noise. Results demonstrated the advantage of natural products for novel fluorescent probes and the great potential of quercetin-3-O-β-D-glucuronide in high-throughput inhibitors screening, GUS-related drug discovery, and disease diagnosis.

Preliminary studies on extraction of propolis using vitamin E d-ɑ-Tocopheryl polyethylene glycol succinate (vitamin E TPGS) and compare their antimicrobial activities

Aims: Phenolic compounds with various biological activities such as antimicrobial, anti-inflammatory and antioxidative activity are considered as key compounds in propolis. In this study, propolis was obtained in Kuantan, Pahang and is known to be collected from stingless honey bee Trigona thoracica. The objective of this study is to extract propolis using surfactant vitamin E d-α-Tocopheryl polyethylene glycol 1000 succinate (Vitamin E TPGS) and evaluate its antimicrobial activity compared to water and ethanolic propolis extracts. Methodology and results: Quantitative determinations of phenolic acid and flavonoid such as caffeic acid and quercetin, respectively in propolis extracts were conducted by using High Performance Liquid Chromatography (HPLC). As a result, 70% ethanol extracted propolis (EEP), water extracted propolis (WEP) and 0.02% vitamin E TPGS extracted propolis successfully demonstrate the presence of hydrophilic caffeic acid, while only 70% EEP and 0.02% vitamin E TPGS extracted propolis show the presence of hydrophobic quercetin. Lastly, antimicrobial testing was conducted towards Staphylococcus aureus by using all three different propolis extracts. Conclusion, significance and impact of study: The results showed EEP and vitamin E TPGS propolis extracts exhibit higher antimicrobial activity compared to the WEP.

Coencapsulation and Stability Evaluation of Hydrophilic and Hydrophobic Bioactive Compounds in a Cagelike Phytoferritin.

Enrichment of multiple bioactive components with different characters into one food substrate simultaneously is a challenge. In this study, the hydrophilic epigallocatechin gallate (EGCG) and the hydrophobic quercetin were simultaneously enriched in the cavity of phytoferritin from red bean seed deprived of iron (apoRBF), a cagelike protein. The interactions of apoRBF with EGCG and quercetin were evaluated by UV/visible absorption, fluorescence, and circular dichroism technologies. By combination of the reversible assembly and urea induced approaches, both EGCG and quercetin were successfully coencapsulated in apoRBF to fabricate four kinds of apoRBF-EGCG-quercetin nanocomplexes FEQ (FEQ1, FEQ2, FEQ3, and FEQ4) with good solubility in aqueous solution. All FEQ samples maintained the typically spherical morphology of ferritin cage with a diameter around 12 nm. Among the four FEQ samples, the FEQ1 prepared by involving a pH 2.0/6.7 transition scheme was more effective in encapsulating EGCG and quercetin molecules than that by the urea induced method. Furthermore, all FEQs facilitated the stability of EGCG and quercetin molecules relative to free ones, and simultaneous coencapsulation of EGCG and quercetin could significantly improve the quercetin stability as compared with that of the free one and quercetin-loaded ferritin (p < 0.05), respectively. This work provides a new scheme to design and fabricate the ferritin based carrier for encapsulation of multiple bioactive components, and it is beneficial for the intensification of multifunction in one food substrate.

Fabrication of stable zein nanoparticles coated with soluble soybean polysaccharide for encapsulation of quercetin

The present work aims to prepare and stabilize zein colloidal nanoparticles using soluble soybean polysaccharide (SSPS) as a stabilizer. A simple antisolvent precipitation method was used to fabricate the zein/SSPS composite nanoparticles at pH 4.0. The results showed that the SSPS-stabilized zein nanoparticles (size around 200 nm, PDI below 0.2) did not aggregate or precipitate at pH 2.0–8.0. And they were also relatively stable for elevated ionic strength and high temperature. Affected by the SSPS coating, the surface hydrophobicity of the zein nanoparticles decreased over a wide pH range. Conditions of forming zein/SSPS nanoparticles were successfully used to encapsulate hydrophobic quercetin (Q). The encapsulation efficiency was greatly improved to 82.5% after SSPS coating, compared to 59.2% for the zein without coating. Besides, the photochemical stability and ABTS+ scavenging ability of Q in zein/SSPS composite nanoparticles were significantly enhanced. This study demonstrates that these composite nanoparticles can be used as all-natural delivery systems for bioactive molecules in food and pharmaceutical formulations.

A targeted nanoplatform co-delivering chemotherapeutic and antiangiogenic drugs as a tool to reverse multidrug resistance in breast cancer

Several obstacles are currently impeding the successful treatment of breast cancer, namely impaired drug accumulation into the tumor site, toxicity to normal cells and narrow therapeutic index of chemotherapy, multidrug resistance (MDR) and the metastatic spread of cancer cells through the blood and lymphatic vessels. In this regard, we designed a novel multifunctional nano-sized drug delivery system based on LyP-1 peptide-modified low-molecular-weight heparin-quercetin conjugate (PLQ). This nanosystem was developed for targeted co-delivery of multiple anticancer drugs to p32-overexpressing tumor cells and peritumoral lymphatic vessels, using LyP-1 peptide as active targeting ligand, with the aim to achieve a targeted combinatorial chemo/angiostatic therapy and MDR reversal. The cellular uptake of PLQ nanoparticles by p32-overexpressing breast cancer cells was significantly higher than nonfunctionalized nanoparticles. Besides, the anti-angiogenic activity of PLQ nanoparticles was proven by the effective inhibition of the bFGF-induced neovascularization in subcutaneous Matrigel plugs. More importantly, PLQ/GA nanoparticles with better targeting ability toward p32-positive tumors, displayed a high antitumor outcome by inhibition of tumor cells proliferation and angiogenesis. Immunohistochemistry and western blot assay showed that PLQ/GA nanoparticles significantly disrupted the lymphatic formation of tumor, and inhibited the P-glycoprotein (P-gp) expression in MCF-7 tumor cells, respectively. In conclusion, PLQ/GA nanoparticles provide a synergistic strategy for effective targeted co-delivery of chemotherapeutic and antiangiogenic agents and reversing MDR and metastasis in breast cancer. Statement of SignificanceHerein, we successfully developed a novel amphiphilic nanomaterial, LyP-1-LMWH-Qu (PLQ) conjugate, consisting of a tumor-targeting moiety LyP-1, a hydrophobic quercetin (a multidrug resistance [MDR]–reversing drug) inner core, and a hydrophilic low-molecular-weight heparin (an antiangiogenic agent) outer shell for encapsulating and delivering a hydrophobic chemotherapeutic agent (gambogic acid). This versatile nanoplatform with multiple targeted features, i.e., dual chemo/angiostatic effects, destruction ability of the peritumoral lymphatic vessels, and reversal of MDR, resulted in a significantly stronger antitumor efficacy and lower toxic side effect than those of nontargeted nanoparticles and the free drug solution. Therefore, this versatile nanosystem might provide a novel insight for the treatment and palliation of breast cancer by targeted co-delivery of chemo/antiangiogenic agents and reversing MDR and metastasis.

Synthesis and characterization of karaya gum-g- poly (acrylic acid) hydrogels and in vitro release of hydrophobic quercetin

Interest in the development of new materials based on natural polysaccharides has grown exponentially in the last decade. Therefore, polysaccharide hydrogels gain striking attention having unique properties. In this study, karaya gum polysaccharide hydrogels have been synthesized using free radical mechanism. In this mechanism, ammonium persulfate (APS) was used as an initiator to form free radicals of karaya gum and acrylic acid while N, N′-methylenebisacrylamide (MBA) was used to crosslink these radicals. The synthesized hydrogels were characterized in terms of structure and properties. The structural evaluation was performed using different techniques. The vanishing of existing and appearance of new functional groups were analyzed using Fourier transform infrared (FTIR) analysis. The physical state of the hydrogel was evaluated using X-ray diffraction analysis while thermal stability and formation of hydrogels were further confirmed using Differential scanning calorimetry (DSC). The morphology study was conducted using Field emission scanning electron microscope (FESEM). Furthermore, mechanical properties of hydrogels were investigated using rheometer and swelling properties were evaluated in water and buffer solutions of pH 7.4 and pH 1.2. Hydrophobic drug loading and structural stability of drug after drug loading are the major challenges in the drug delivery. Hydrophobic drug quercetin was loaded, and in vitro release studies were conducted. The quercetin release showed complete non-Fickian transport mechanism. All these results revealed the successful synthesis of hydrogels and potential applications of hydrogels in hydrophobic drug delivery.

Pluronic-SAILs (surface active ionic liquids) mixed micelles as efficient hydrophobic quercetin drug carriers

The present manuscript reports a systematic investigation on the solubilization of hydrophobic drug Quercetin (QCT) in pluronic F108 and its mixed micelles with surface active ionic liquids (SAILs) having same alkyl chain length but different hydrophobic head groups viz. 1-dodecyl-3-methylimidazolium bromide [Mim]; N-dodecyl-Nmethylpiperidinium bromide, [Pip]; N-dodecyl-Nmethylpyrrolidinium bromide, [Pyr]. Employing UV–visible spectroscopy, we have determined the solubility, loading efficiency and partition coefficient of QCT in the pluronic F108 and F108-SAILs mixed micelles. The F108-SAIL mixed micellar system possessed higher solubilization capacity for QCT. Further, the effect of varying composition of mixed micelles on the solubilization of QCT has also been evaluated and discussed in detail. A significant difference between the hydrodynamic diameter (Dh) of loaded and unloaded F108 as well as F108-SAILs mixed micelles confirmed that QCT has been solubilized in these micelles. Differential pulse voltammetry (DPV) measurements have been successfully employed to determine the possible location of the QCT in the both pluronic F108 and pluronic F108-SAILs mixed micelles. These measurements indicated that most of QCT is solubilized in the core of the F108 and F108-SAILs mixed micelles. In vitro drug release study of three different F108-SAILs mixed micellar formulations show sustained release behavior according to their interaction with the QCT. Higher anticancer effects were observed in the case of micellar QCT than the free QCT confirm the efficiency of the prepared formulations. The results demonstrated that the composition of mixed micelles had a profound effect on solubilization capacity and the drug release behavior from the F108-SAILs mixed micelles can be easily tuned by changing the head group of SAILs.

Co-delivery of doxorubicin and quercetin via mPEG–PLGA copolymer assembly for synergistic anti-tumor efficacy and reducing cardio-toxicity

Quercetin (Que) is a natural multifunctional bioflavonoid, and has shown great potential for reducing adverse side effects and enhancing anti-tumor efficacy of chemotherapeutic drugs. However, its clinical application is limited due to very low solubility and structural instability in physiological systems. Herein, we co-delivered hydrophobic quercetin and hydrophilic doxorubicin (Dox) by developing a biocompatible nanocarrier comprising of an amphiphilic polymer, methoxy poly(ethylene glycol) and poly(D, L-lactide-co-glycolide), respectively. The antitumor and prophylactic efficacy of this system was evaluated in cellular and animal models. Our findings illustrated that the Dox-Que nanoparticulate formulation protected normal vascular endothelial cells from either free or nanoparticulate doxorubicin-induced cytotoxicity and increased cancer cell death. Compared with free doxorubicin and its nanoformulation, co-delivery of quercetin and doxorubicin using our nanosystem synergistically inhibited tumor growth, while maintaining normal levels of cardiac function indicators in serum and recovering the histopathological damages in heart tissue. This study demonstrates a promising strategy for enhancing anti-cancer drug efficacy and reducing nanoparticulate chemotherapy-induced toxicity on normal tissues.

Controlled drug release using ascorbate-responsive quercetin-conjugated alginate hydrogels

In this paper, we report a new strategy for controlled cargo release using quercetin-conjugated alginate (Alg) hydrogels that has enhanced hydrogel stability and can release cargo molecules through on-demand metal cation reduction by a biological reducing agent, ascorbate. By conjugating hydrophobic quercetin to the Alg backbone, hydrogel stability was increased. The encapsulated cargos were released on demand through reduction of cross-linking Fe(III) ions by ascorbate, harnessing the differences in cross-linking capability between Fe(II) and Fe(III). We found that encapsulated fluorescein in quercetin-conjugated Alg hydrogels was released much slower than that in hydrogels without quercetin conjugation. In addition, the stability of the hydrogels and the release of encapsulated fluorescein were controlled by modulating oxidation state of Fe using ascorbate. We validated our strategy by demonstrating the enhanced cancer cell killing of the doxorubicin-encapsulated hydrogels upon treatment with ascorbate. We believe that the strategy would be used as an effective tool for the anticancer drug delivery that can be controlled by ascorbate as overcoming the drawback of Alg hydrogels.

Methoxy poly(ethylene glycol)-poly(lactide) nanoparticles encapsulating quercetin act as an effective anticancer agent by inducing apoptosis in breast cancer.

To overcome the therapeutic restrictions offered by hydrophobic quercetin (Qu), this study aims to synthesize MPEG-PLA encapsulated Qu nanoparticle and to evaluate their anticancer efficacy. In vitro anticancer potential and apoptotic studies were done by cell cytotoxicity assay and flow cytometry, respectively. MPEG-PLA-Qu nanoparticles were evaluated for anticancer efficacy in vivo using xenograft mice model. TUNEL assay was performed to observe the frequency of apoptotic cells in vivo. The hydrodynamic particle size, polydispersity index, zeta potential and drug loading % of MPEG-PLA-Qu nanoparticle was 155.3 ± 3.2 nm, 0.2 ± 0.05, -3.14 mV and 5.3 ± 1.1%, respectively. Also, MPEG-PLA-Qu showed sustained drug release for 10 days. In vitro results showed that MPEG-PLA-Qu could efficiently induce apoptosis in triple negative breast cancer cell line (MDA-MB-231) with higher amount of quercetin in cell lysate treated with MPEG-PLA-Qu in comparison to free quercetin. In xenograft model for breast cancer, peritumorally injected MPEG-PLA-Qu significantly inhibited the tumor growth. Moreover, TUNEL assay showed more occurrence of apoptotic cells in MPEG-PLA-Qu treated tumors compared to free quercetin at similar dose. Our data suggest that MPEG-PLA-Qu nanoparticle can have a promising clinical potential for the treatment of breast cancer.

Spectral and Acid-Base Properties of Hydroxyflavones in Micellar Solutions of Cationic Surfactants

It has been shown that the spectral characteristics (intensity, position of the absorption band) and the acid-base properties in a series of structurally similar hydroxyfl avones depend on the concentration of the cationic surfactants miramistin and decamethoxin in aqueous solutions, and the extent of their changes is more pronounced for hydrophobic quercetin than for hydrophilic rutin. For the fi rst time, we have determined the apparent dissociation constants of quercetin and rutin in solutions of these cationic surfactants (pKa1) over a broad concentration range and we have established that they decrease in the series water-decamethoxin-miramistin. Introduction. The natural hydroxyfl avones (HFl) rutin (Rt) and its aglycone quercetin (Qu) are widely used in medicine (1-3), since they exhibit high antioxidant, anti-infl ammatory, antiviral activity and the ability to improve capillary resistance. It was shown earlier (4, 5) that in organized media of polyvinylpyrrolidone and serum albumins, a decrease occurs in the dissociation constants of hydroxyfl avones compared with aqueous solutions, as a result of formation of supramolecular complexes in these systems, evidence for which is also the bathochromic shifts of bands in the absorption spectra of quercetin and rutin over a broad solution pH range. As the object of this study, we selected self-organizing supramolecular micellar systems based on cationic surfactants, which are organized reaction media capable of affecting the solubility and other physicochemical properties of substances (spectral, acid-base, adsorption, etc.), the occurrence of chemical processes, and also can be promising systems for modeling biosystems (6, 7). Today some of the most effective broad-spectrum antiseptics are the cationic surfactants miramistin (MR) and decamethoxin (DCM) (1). No quantitative description of the effect of these cationic surfactants on the spectral and acid- base properties of hydroxyfl avones is available in the literature, even though taking into account protolytic interactions is of scientifi c and practical importance in medical practice for developing and using drugs based on such systems. The aim of this work was to study the effect of the cationic surfactants miramistin and decamethoxin over a broad concentration range on the spectral and acid-base properties of quercetin and rutin in the physiological pH range. The experiment. We used miramistin (Infamed), decamethoxin (pilot production of the Institute of Organic Chemistry, National Academy of Sciences of Ukraine), quercetin and rutin (Sichuan Xieli Pharmaceutical Co. Ltd., China), analytical grade. Stock solutions were prepared by dissolving exactly weighed amounts of the preparations. In all the experiments, the hydroxyfl avone concentration was 2·10 -5 M, ethanol 4%, μ = 0.2 (NaCl). The electronic absorption spectra of the solutions were measured on a Specord M-40 spectrophotometer (Carl Zeiss Jena, Germany) using a cuvet with l = 1 cm. Starting from the values given in the literature for the fi rst (pKa1) and second (pKa2) thermodynamic dissociation constants for quercetin: pKa1 = 6.74 (8), 7.03 (9), 7.3 (10), 6.62 (11), 8.21 (12); pKa2 = 9.02 (8), 9.15 (9), 9.7 (11) and for rutin: pKa1 = 7.40 (13), 8.96 (12); pKa2 = 8.70 (13), we see that in the physiological pH range (pH = 3-8) for the solution, dissociation of one hydroxyl group of the hydroxyfl avone occurs. For a quantitative estimate of the effect of cationic surfactants on this process, we determined the dissociation constants of the hydroxyfl avones (pKa1) by the standard spectrophotometric method (14) over a broad concentration range for miramistin and decamethoxin, with uncertainty ≤0.04.

Dependence of the solubility of natural flavonoids in water on the concentration of miramistin, polyvinylpyrrolidone, and human serum albumin

In organized media of the cationic surfactant miramistin and the polymers polyvinylpyrrolidone and human serum albumin, the solubility of natural flavonoids quercetin and rutin increased by one or two orders of magnitude. The increase was more significant for hydrophobic quercetin than for hydrophilic rutin. The solubility also depended on the structure and self-organization of molecules in organized media and the site of flavonoids in them. The calculated binding constants increased in the series polyvinylpyrrolidone < miramistin < human serum albumin.

Dual-functionalization based on combination of quercetin compound and rare earth nanoparticle

While the nanoparticles like La2O3 and other rare earth oxides were believed to be able to provide effective scavenging hydroxyl radical. Quercetin, a hydrophobic agent, showed some potential antibacterial activity. The present work successfully performed the surface modification of rare earth nanoparticle using facile and general strategy. In specific, the hydrophobic quercetin was grafted on the rare earth nanoparticle through the coupling with silane. The surface modified nanoparticle was characterized by Fourier-transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The surface modification helped to retain both the scavenging hydroxyl radical property of rare earth nanoparticle and the antibacterial activity of quercetin. This dual-function properties showed potential for application in the development of biomedicine such as antioxidant, anti-inflammatory, antibacterial and anticancer.

The flavonols quercetin, rutin and morin in DNA solution: UV–vis dichroic (and mid-infrared) analysis explain the possible association between the biopolymer and a nucleophilic vegetable-dye

Previous studies showed evidence that quercetin can bind DNA by intercalation [R. Solimani et al., J. Agric. Food Chem. 43 (1995) 876–882] and a comparison with the flavanol dihydroquercetin indicated that the interaction is correlated to the planarity and hydrophobicity of the benzopyranic-4-one plane [R. Solimani, Int. J. Biol. Macromol. 18 (1996) 287–295]. In this study flow linear dichroism (LD) spectra of the hydrophobic quercetin were compared with hydrophilic aglycoside morin and 3-glycoside rutin in the same conditions: [DNA]=3.1·10 −2 mol/l phosphate, [dye]=(1.0–4.0)·10 −4 mol/l. Morin and rutin in an aqueous environment showed the same behaviour as quercetin in buffer–ethanol (70:30, v/v) solution, with their common benzopyranic-4-one part within the biopolymer. The LD R values (LD normalised to the relative isotropic absorption) indicated a greater affinity of the quercetin for the DNA. Comparison of the LD R of morin and rutin showed a ratio LD morin R/LD rutin R≈1.1–1.2 very close to unity and this suggests the localisation of the 3-rutinoside of rutin outside the intercalation site. Dichroic measurements recorded in extreme conditions of concentration partly clarified the sequences of interaction between quercetin and DNA in solution which shows the prototypical behaviour of the flavonolic group. This consists of an initial weak external association, where an electrostatic component is excluded, and which can evolve to intercalation changing the DNA concentration, whereas the quantity of the flavonol influences relatively the association. The carbonylic region of the benzopyranic-4-one chromophore is probably localised outside the intercalation site. This was suggested by indirect infrared (attenuated total reflection ATR) data of the quercetin–ethanol solution: the presence of free and chelated carbonyl determines a greater density of negative charges in this region of the chromophore, with the consequent lower probability of this portion penetrating the external polyanionic perimeter of the DNA. A simple approach to determine the order of magnitude of the anisotropic band II of the flavonols completely covered by the more intense DNA band at 260 nm, was also proposed. The low number of intercalated chromophores did not determine an alteration of the flexibility and hydrodynamic behaviour of the biopolymer and this can be correlated to a biological consideration: the flavonols probably do not interfere with the genetic functionality of the DNA. In contrast, the potentially close relationship between these nucleophilic dyes and the biopolymer, shown in this study, suggests a protective role on the nucleophilic groups of the DNA, which are a target of free radicals and the reactive electrophilic groups.