Influence of the Phenological Stage and Harvest Date on the Bioactive Compounds Content of Green Pepper Fruit

Green pepper fruit is often consumed before it is completely ripe. However, the influence of the phenological stage in which the green pepper is consumed as a potential influencing factor in its bioactive compounds content and antioxidant capacity remains unknown. In addition, no literature is available concerning the bioactive compounds changes in 'Lamuyo' green peppers along its developmental and growth cycle. For this, two different approaches have been carried out, one using twelve different phenological stages (S1 to S12), and in the other, seven different harvest dates (from 27 February to 20 April). Moreover, bioactive compounds changes during 21 days of postharvest storage at 8 °C were investigated. In this study, bioactive compounds (ascorbic acid, dehydroascorbic acid, and total phenolic content) and the total hydrophilic and lipophilic (TAA-H and TAA-L) antioxidant activity were analysed. In addition, total soluble solids, total acidity, individual sugars, and organic acids were determined. Vitamin C levels increased along the phenological stages and harvest dates due to significant increases in ascorbic and dehydroascorbic acid levels. Our results show that the total phenol content decreases as vegetables develop and subsequently increases both as ripening begins and by the last harvest date. Furthermore, TAA-H was also greater by the phenological stage S12 and the 20 April harvest date. In conclusion, the phenological stage and harvest date are key factors that significantly influence the bioactive compounds of green peppers, and those that appear by S12 and 20 April could be more beneficial to health.

Lithium cobalt phosphate electrode for the simultaneous determination of ascorbic acid, dopamine, and serum uric acid by differential pulse voltammetry

Lithium cobalt phosphate (LCP) was prepared and modified on the surface of glassy carbon electrode (GCE) to fabricate the electrochemical sensor (LCP/GCE) for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and serum uric acid (UA). The homogenous incorporation of carbon improved the conductivity of LCP. Benefiting from the small particle size distribution, LCP/GCE has a large active surface and responds to AA, DA, and UA sensitively and rapidly. For the simultaneous detection with differential pulse voltammetry the anodic peaks of AA, DA, and UA were well-separated and appeared at ~0 V, ~0.19 V, and ~ 0.33 V (vs. Ag/AgCl), respectively. The linear responses toward AA, DA, and UA were in the range 10 μM-8.0 mM, 10 nM-10 μM, and 0.020 μM-25 μM; the detection limits were estimated to be 8.10 μM, 7.50 nM, and 22.7 nM (S/N = 3), respectively. The excellent selectivity and reproducibility of LCP/GCE enable serum UA to be detected without the interference of AA and DA. The recoveries of DA and AA in the serum sample were in the range 95 to 111%. The results indicate that LCP has the potential to be developed as the sensing devices to be applied to in vitro diagnosis. The lithium-ion battery cathodic material, LCP with the excellent adsorption and catalytic behavior, was utilized to fabricate the electrochemical sensor for the sensitive and simultaneous detection of AA, DA, and UA, which achieved the low detection limits and the wide concentration ranges. LCP/GCE can be used for the quantitative detection of serum UA without the interference of DA and AA. In addition, the recoveries of DA and AA in human serum were satisfactory, which illustrate the reliability of LCP/GCE to be applied to in vitro diagnosis.

Molecular Mechanisms on the Selectivity Enhancement of Ascorbic Acid, Dopamine, and Uric Acid by Serine Oligomers Decoration on Graphene Oxide: A Molecular Dynamics Study

The selectivity in the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) has been an open problem in the biosensing field. Many surface modification methods were carried out for glassy carbon electrodes (GCE), including the use of graphene oxide and amino acids as a selective layer. In this work, molecular dynamics (MD) simulations were performed to investigate the role of serine oligomers on the selectivity of the AA, DA, and UA analytes. Our models consisted of a graphene oxide (GO) sheet under a solvent environment. Serine tetramers were added into the simulation box and were adsorbed on the GO surface. Then, the adsorption of each analyte on the mixed surface was monitored from MD trajectories. It was found that the adsorption of AA was preferred by serine oligomers due to the largest number of hydrogen-bond forming functional groups of AA, causing a 10-fold increase of hydrogen bonds by the tetraserine adsorption layer. UA was the least preferred due to its highest aromaticity. Finally, the role of hydrogen bonds on the electron transfer selectivity of biosensors was discussed with some previous studies. AA radicals received electrons from serine through hydrogen bonds that promoted oxidation reaction and caused the negative shifts and separation of the oxidation potential in experiments, as DA and UA were less affected by serine. Agreement of the in vitro and in silico results could lead to other in silico designs of selective layers to detect other types of analyte molecules.

Polyphenols, L-Ascorbic Acid, and Antioxidant Activity in Wines from Rose Fruits (Rosa rugosa)

The aim of the present study was to determine the influence of the winemaking process on the antioxidant potential and content of phenolic compounds and L-ascorbic acid in wines from the fruits of Rosa rugosa. The results obtained in this study clearly indicate that the fruits of the Rosa rugosa are a desirable raw material for the production of fruit wine. The parameters of the technological process of producing wines from rose fruits had a diversified influence on the tested quality characteristics. Aged wines contained phenolics levels of 473–958 mg/100 mL GAE. The final concentrations of ascorbic acid ranged from 61 to 155 mg/100 mL for the different variants of the wine. Wines revealed high antioxidant activity in assay with DPPH. On the basis of the obtained results, it can be assumed that all the applied variants of the winemaking process are suitable for rose fruit wine. Each variant ensured at least the stability of the antioxidant capacity.

Degradation of Codium cylindricum polysaccharides by H2O2-Vc-ultrasonic and H2O2-Fe2+-ultrasonic treatment: Structural characterization and antioxidant activity

In this study, two degraded polysaccharides were obtained by H₂O₂-Vc-ultrasonic and H₂O₂-Fe²⁺-ultrasonic treatment from Codium cylindricum. The basic structure of polysaccharides was characterized and the relationship between structure and antioxidant activity was studied. FTIR spectrum indicated that the degraded polysaccharides had similar functional groups (OH, CH, CO group) with ordinary polysaccharides. LC-MS analysis showed that the degraded polysaccharides were composed of the same monosaccharide units (mannose, galactose, arabinose, glucose, ribose) with Codium cylindricum polysaccharides, but the molar ratio was different. Meanwhile, the molecular weight and morphological feature of polysaccharides had been changed after degradation. Additionally, the antioxidant activity assay revealed that two degraded polysaccharides with lower molecular weight possessed better antioxidant property than ordinary polysaccharides. These results suggested that the basic structure of polysaccharides had not been damaged by two degradation methods, while the antioxidant activity was significantly enhanced.

Effect of Physiological Concentrations of Vitamin C on the Inhibitation of Hydroxyl Radical Induced Light Emission from Fe2+-EGTA-H2O2 and Fe3+-EGTA-H2O2 Systems In Vitro

Ascorbic acid (AA) has antioxidant properties. However, in the presence of Fe²⁺/Fe³⁺ ions and H₂O₂, it may behave as a pro-oxidant by accelerating and enhancing the formation of hydroxyl radicals (^•OH). Therefore, in this study we evaluated the effect of AA at concentrations of 1 to 200 µmol/L on ^•OH-induced light emission (at a pH of 7.4 and temperature of 37 °C) from 92.6 µmol/L Fe²⁺—185.2 µmol/L EGTA (ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid)—2.6 mmol/L H₂O₂, and 92.6 µmol/L Fe³⁺—185.2 µmol/L EGTA—2.6 mmol/L H₂O₂ systems. Dehydroascorbic acid (DHAA) at the same range of concentrations served as the reference compound. Light emission was measured with multitube luminometer (AutoLumat Plus LB 953) for 120 s after automatic injection of H₂O₂. AA at concentrations of 1 to 50 µmol/L and of 1 to 75 µmol/L completely inhibited light emission from Fe²⁺-EGTA-H₂O₂ and Fe³⁺-EGTA-H₂O₂, respectively. Concentrations of 100 and 200 µmol/L did not affect chemiluminescence of Fe³⁺-EGTA-H₂O₂ but tended to increase light emission from Fe²⁺-EGTA-H₂O₂. DHAA at concentrations of 1 to 100 µmol/L had no effect on chemiluminescence of both systems. These results indicate that AA at physiological concentrations exhibits strong antioxidant activity in the presence of chelated iron and H₂O₂.

Fabrication of Adipose-Derived Stem Cell-Based Self-Assembled Scaffold under Hypoxia and Mechanical Stimulation for Urethral Tissue Engineering

Long urethral strictures are often treated with autologous genital skin and buccal mucosa grafts; however, risk of hair ingrowth and donor site morbidity, restrict their application. To overcome this, we introduced a tissue-engineered human urethra comprising adipose-derived stem cell (ASC)-based self-assembled scaffold, human urothelial cells (UCs) and smooth muscle cells (SMCs). ASCs were cultured with ascorbic acid to stimulate extracellular matrix (ECM) production. The scaffold (ECM) was stained with collagen type-I antibody and the thickness was measured under a confocal microscope. Results showed that the thickest scaffold (28.06 ± 0.59 μm) was achieved with 3 × 10⁴ cells/cm² seeding density, 100 μg/mL ascorbic acid concentration under hypoxic and dynamic culture condition. The biocompatibility assessment showed that UCs and SMCs seeded on the scaffold could proliferate and maintain the expression of their markers (CK7, CK20, UPIa, and UPII) and (α-SMA, MHC and Smootheline), respectively, after 14 days of in vitro culture. ECM gene expression analysis showed that the ASC and dermal fibroblast-based scaffolds (control) were comparable. The ASC-based scaffold can be handled and removed from the plate. This suggests that multiple layers of scaffold can be stacked to form the urothelium (seeded with UCs), submucosal layer (ASCs only), and smooth muscle layer (seeded with SMCs) and has the potential to be developed into a fully functional human urethra for urethral reconstructive surgeries.

Graphene-Based Sensors for the Detection of Bioactive Compounds: A Review

Over the last years, different nanomaterials have been investigated to design highly selective and sensitive sensors, reaching nano/picomolar concentrations of biomolecules, which is crucial for medical sciences and the healthcare industry in order to assess physiological and metabolic parameters. The discovery of graphene (G) has unexpectedly impulsed research on developing cost-effective electrode materials owed to its unique physical and chemical properties, including high specific surface area, elevated carrier mobility, exceptional electrical and thermal conductivity, strong stiffness and strength combined with flexibility and optical transparency. G and its derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), are becoming an important class of nanomaterials in the area of optical and electrochemical sensors. The presence of oxygenated functional groups makes GO nanosheets amphiphilic, facilitating chemical functionalization. G-based nanomaterials can be easily combined with different types of inorganic nanoparticles, including metals and metal oxides, quantum dots, organic polymers, and biomolecules, to yield a wide range of nanocomposites with enhanced sensitivity for sensor applications. This review provides an overview of recent research on G-based nanocomposites for the detection of bioactive compounds, providing insights on the unique advantages offered by G and its derivatives. Their synthesis process, functionalization routes, and main properties are summarized, and the main challenges are also discussed. The antioxidants selected for this review are melatonin, gallic acid, tannic acid, resveratrol, oleuropein, hydroxytyrosol, tocopherol, ascorbic acid, and curcumin. They were chosen owed to their beneficial properties for human health, including antibiotic, antiviral, cardiovascular protector, anticancer, anti-inflammatory, cytoprotective, neuroprotective, antiageing, antidegenerative, and antiallergic capacity. The sensitivity and selectivity of G-based electrochemical and fluorescent sensors are also examined. Finally, the future outlook for the development of G-based sensors for this type of biocompounds is outlined.

Novel Multifunctional Ascorbic Triazole Derivatives for Amyloidogenic Pathway Inhibition, Anti-Inflammation, and Neuroprotection

Alzheimer's disease (AD) is a common neurodegenerative disorder. The number of patients with AD is projected to reach 152 million by 2050. Donepezil, rivastigmine, galantamine, and memantine are the only four drugs currently approved by the United States Food and Drug Administration for AD treatment. However, these drugs can only alleviate AD symptoms. Thus, this research focuses on the discovery of novel lead compounds that possess multitarget regulation of AD etiopathology relating to amyloid cascade. The ascorbic acid structure has been designated as a core functional domain due to several characteristics, including antioxidant activities, amyloid aggregation inhibition, and the ability to be transported to the brain and neurons. Multifunctional ascorbic derivatives were synthesized by copper (I)-catalyzed azide-alkyne cycloaddition reaction (click chemistry). The in vitro and cell-based assays showed that compounds 2c and 5c exhibited prominent multifunctional activities as beta-secretase 1 inhibitors, amyloid aggregation inhibitors, and antioxidant, neuroprotectant, and anti-inflammatory agents. Significant changes in activities promoting neuroprotection and anti-inflammation were observed at a considerably low concentration at a nanomolar level. Moreover, an in silico study showed that compounds 2c and 5c were capable of being permeated across the blood-brain barrier by sodium-dependent vitamin C transporter-2.

Erythorbyl fatty acid ester as a multi-functional food emulsifier: Enzymatic synthesis, chemical identification, and functional characterization of erythorbyl myristate

Erythorbyl myristate (EM), a potential multi-functional food emulsifier, was newly synthesized by immobilized lipase-catalyzed esterification between antioxidative erythorbic acid and antibacterial myristic acid. The yield and productivity of EM were 56.13 ± 2.51 mg EM/g myristic acid and 1.76 ± 0.08 mM/h, respectively. The molecular structure of EM was identified as (R)-2-((R)-3,4-dihydroxy-5-oxo-2,5-dihydrofuran-2-yl)-2-hydroxyethyl tetradecanoate using HPLC-ESI/MS and 2D [¹H-¹H] NMR COSY. The hydrophilic-lipophilic balance of EM was 11.5, suggesting that EM could be proper to stabilize oil-in-water emulsions. Moreover, isothermal titration calorimetry demonstrated the micellar thermodynamic behavior of EM and determined its critical micelle concentration (0.36 mM). In terms of antioxidative property, EM exhibited the radical scavenging activity against DPPH (EC₅₀: 35.47 ± 0.13 μM) and ABTS (EC₅₀: 36.45 ± 1.98 μM) radicals. Finally, EM showed bacteriostatic and bactericidal activities against Gram-positive foodborne pathogens (minimum inhibitory concentration: 0.06-0.60 mM; minimum bactericidal concentration: 0.07-0.93 mM).

Exploring the Toxicity, Lung Distribution, and Cellular Uptake of Rifampicin and Ascorbic Acid-Loaded Alginate Nanoparticles as Therapeutic Treatment of Lung Intracellular Infections

Nanotechnology is a very promising technological tool to combat health problems associated with the loss of effectiveness of currently used antibiotics. Previously, we developed a formulation consisting of a chitosan and tween 80-decorated alginate nanocarrier that encapsulates rifampicin and the antioxidant ascorbic acid (RIF/ASC), intended for the treatment of respiratory intracellular infections. Here, we investigated the effects of RIF/ASC-loaded NPs on the respiratory mucus and the pulmonary surfactant. In addition, we evaluated their cytotoxicity for lung cells in vitro, and their biodistribution on rat lungs in vivo after their intratracheal administration. Findings herein demonstrated that RIF/ASC-loaded NPs display a favorable lung biocompatibility profile and a uniform distribution throughout lung lobules. RIF/ASC-loaded NPs were mainly uptaken by lung macrophages, their primary target. In summary, findings show that our novel designed RIF/ASC NPs could be a suitable system for antibiotic lung administration with promising perspectives for the treatment of pulmonary intracellular infections.

Enhanced nuclear-spin hyperpolarization of amino acids and proteins via reductive radical quenchers

Low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) has recently emerged as an effective tool for the hyperpolarization of aromatic amino acids in solution, either in isolation or within proteins. One factor limiting the maximum achievable signal-to-noise ratio in LC-photo-CIDNP is the progressive degradation of the target molecule and photosensitizer upon long-term optical irradiation. Fortunately, this effect does not cause spectral distortions but leads to a progressively smaller signal buildup upon long-term data-collection (e.g. 500 nM tryptophan on a 600 MHz spectrometer after ca. 200 scans). Given that it is generally desirable to minimize the extent of photodamage, we report that low-μM amounts of the reductive radical quenchers vitamin C (VC, i.e., ascorbic acid) or 2-mercaptoethylamine (MEA) enable LC-photo-CIDNP data to be acquired for significantly longer time than ever possible before. This approach increases the sensitivity of LC-photo-CIDNP by more than 100%, with larger enhancement factors achieved in experiments involving more transients. Our results are consistent with VC and MEA acting primarily by reducing transient free radicals of the NMR molecule of interest, thus attenuating the extent of photodamage. The benefits of this reductive radical-quencher approach are highlighted by the ability to collect long-term high-resolution 2D 1H-13C LC-photo-CIDNP data on a dilute sample of the drkN SH3 protein (5 μM).

Dioleylphosphatidylcholine increases the antioxidant properties of ascorbyl palmitate in bulk oils compared to other hydrophilic and lipophilic antioxidants

Effects of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and moisture on the solubility of hydrophilic and lipophilic antioxidants were evaluated in medium-chain triacylglycerol (MCT) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) reactivity. Next, we assessed the oxidative stability of antioxidant-containing corn oil depending on the presence of DOPC. The critical micelle concentration (CMC) of DOPC decreased when the moisture content was increased from 300 to 495 mg/kg oil and gradually increased when the moisture was further increased to 2122 mg/kg oil. As the DOPC concentration increased, the DPPH reactivity of ascorbyl palmitate in the control MCT increased by 10.23-fold, whereas that of the ascorbic acid and α-tocopherol was slightly affected both by the DOPC and moisture content. Presence of DOPC significantly increased the oxidative stability of ascorbyl palmitate-containing corn oil (p < 0.05), whereas these synergistic antioxidant effects were not observed in ascorbic acid-or α-tocopherol-containing corn oil. In conclusion, DOPC displays a synergistic antioxidant effect with ascorbyl palmitate in bulk oil.

2-O-β-d-Glucopyranosyl l-Ascorbic Acid, a Stable Form of Vitamin C, Is Widespread in Crop Plants

2-O-β-d-Glucopyranosyl l-ascorbic acid (AA-2βG) is a stable, bioavailable vitamin C (AA) derivative. We report the distribution and seasonal variation of AA-2βG in apples and its occurrence in other domesticated crops and in wild harvested Ma̅ori foods. Liquid chromatography-mass spectrometry analyses showed high AA-2βG concentrations in crab apples (Malus sylvestris) but low concentrations in domesticated apples. Leaves of crab and domesticated apple cultivars contained similar intermediate AA-2βG concentrations. Fruits and leaves of other crops were analyzed: mainly Rosaceae but also Actinidiaceae and Ericaceae. AA-2βG was detected in all leaves (0.5-6.1 mg/100 g fr. wt.) but was at lower concentrations in most fruits (0.0-0.5 mg/100 g fr. wt.) except for crab apples (79.4 mg/100 g fr. wt.). Ma̅ori foods from Solanaceae, Piperaceae, Asteraceae, and a fern of Aspleniaceae also contained AA-2βG. This extensive occurrence suggests a general role in AA metabolism for AA-2βG.

Voltammetric sensor based on long alkyl chain tetraalkylammonium ionic liquids comprising ascorbate anion for determination of nitrite

An electrochemical sensor was fabricated utilizing ionic liquids possessing cations with long alkyl chains such as trimethyl octadecylammonium and behenyl trimethylammonium and ascorbate anion. The ionic liquids were drop-coated onto the electrode. Thin modifying layers were prepared. Cyclic voltammetric investigations revealed electrostatic interactions between the electrochemical probes and the modified surface, proving that a positive charge was established at the film surface. Hence, negatively charged species such as nitrite can be pre-concentrated on the surface of presented modified electrodes. The fabricated electrodes have been used as a voltammetric sensor for nitrite. Due to the electrostatic accumulation properties of long alkyl cation, the assay exhibits a remarkable improvement in the voltammetric response toward nitrite oxidation. The influence of pH on the electrode response was thoroughly investigated, and the mechanism of the electrode was established. The developed sensor showed a linear electrochemical response in the range 1.0–50 μM with a detection limit of 0.1 μM. The electrode revealed good storage stability, reproducibility, and anti-interference ability. The determination of nitrite performed in curing salts brought satisfactory results.

Effect of dexamethasone as osteogenic supplementation in in vitro osteogenic differentiation of stem cells from human exfoliated deciduous teeth

In in vitro culture systems, dexamethasone (DEX) has been applied with ascorbic acid (ASC) and β-glycerophosphate (βGLY) as culture media supplementation to induce osteogenic differentiation of mesenchymal stem cells. However, there are some inconsistencies regarding the role of DEX as osteogenic media supplementation. Therefore, this study verified the influence of DEX culture media supplementation on the osteogenic differentiation, especially the capacity to mineralize the extracellular matrix of stem cells from human exfoliated deciduous teeth (SHED). Five groups were established: G1-SHED + Dulbecco's Modified Eagles' Medium (DMEM) + fetal bovine serum (FBS); G2-SHED + DMEM + FBS + DEX; G3-SHED + DMEM + FBS + ASC + βGLY; G4-SHED + DMEM + FBS + ASC + βGLY + DEX; G5-MC3T3-E1 + α Minimal Essential Medium (MEM) + FBS + ASC + βGLY. DNA content, alkaline phosphatase (ALP) activity, free calcium quantification in the extracellular medium, and extracellular matrix mineralization quantification through staining with von Kossa, alizarin red, and tetracycline were performed on days 7 and 21. Osteogenic media supplemented with ASC and β-GLY demonstrated similar effects on SHED in the presence or absence of DEX for DNA content (day 21) and capacity to mineralize the extracellular matrix according to alizarin red and tetracycline quantifications (day 21). In addition, the presence of DEX in the osteogenic medium promoted less ALP activity (day 7) and extracellular matrix mineralization according to the von Kossa assay (day 21), and more free calcium quantification at extracellular medium (day 21). In summary, the presence of DEX in the osteogenic media supplementation did not interfere with SHED commitment into mineral matrix depositor cells. We suggest that DEX may be omitted from culture media supplementation for SHED osteogenic differentiation in vitro studies.

Addition of lemon before boiling chlorinated tap water: A strategy to control halogenated disinfection byproducts

Chlorine disinfection is required to inactivate pathogens in drinking water, but it inevitably generates potentially toxic halogenated disinfection byproducts (halo-DBPs). A previous study has reported that the addition of ascorbate to tap water before boiling could significantly decrease the concentration of overall halo-DBPs in the boiled water. Since the fruit lemon is rich in vitamin C (i.e., ascorbic acid), adding it to tap water followed by heating and boiling in an effort to decrease levels of halo-DBPs was investigated in this study. We examined three approaches that produce lemon water: (i) adding lemon to tap water at room temperature, termed "Lemon"; (ii) adding lemon to boiled tap water (at 100 °C) and then cooling to room temperature, termed "Boiling + Lemon"; and (iii) adding lemon to tap water then boiling and cooling to room temperature, termed "Lemon + Boiling". The concentrations of total and individual halo-DBPs in the resultant water samples were quantified with high-performance liquid chromatography-tandem mass spectrometry and the cytotoxicity of DBP mixtures extracted from the water samples was evaluated using human epithelial colorectal adenocarcinoma Caco-2 cells and hepatoma HepG2 cells. Our results show that the "Lemon + Boiling" approach substantially decreased the concentrations of halo-DBPs and the cytotoxicity of tap water. This strategy could be applied to control halo-DBPs, as well as to lower the adverse health effects of halo-DBPs on humans through tap water ingestion.

Laser Access to Quercetin Radicals and Their Repair by Co-antioxidants

We have demonstrated the feasibility and ease of producing quercetin radicals by photoionization with a pulsed 355 nm laser. A conversion efficiency into radicals of 0.4 is routinely achieved throughout the pH range investigated (pH 2-9), and the radical generation is completed within a few ns. No precursor other than the parent compound is needed, and the ionization by-products do not interfere with the further fate of the radicals. With this generation method, we have characterized the quercetin radicals and studied the kinetics of their repairs by co-antioxidants such as ascorbate and 4-aminophenol. Bell-shaped pH dependences of the observed rate constants reflect opposite trends in the availability of the reacting protonation forms of radical and co-antioxidant and even at their maxima mask the much higher true rate constants. Kinetic isotope effects identify the repairs as proton-coupled electron transfers. An examination of which co-antioxidants are capable of repairing the quercetin radicals and which are not confines the bond dissociation energies of quercetin and its monoanion experimentally to 75-77 kcal mol-1 and 72-75 kcal mol-1 , a much narrower interval in the case of the former than previously estimated by theoretical calculations.

In Situ Synthesis of FeOCl in Hollow Dendritic Mesoporous Organosilicon for Ascorbic Acid-Enhanced and MR Imaging-Guided Chemodynamic Therapy in Neutral pH Conditions

Chemodynamic therapy (CDT) based on the Fenton reaction is a promising strategy for nonlight cancer treatment. However, the traditional Fenton reaction is only efficient in strongly acidic conditions (pH = 2-4), resulting in the limited curative effect in a weakly acidic tumor microenvironment (TME). Herein, we first developed a simple in situ growth method to confine FeOCl nanosheets into hollow dendritic mesoporous organosilicon (H-DMOS) nanoparticles to obtain FeOCl@H-DMOS nanospheres. Ascorbic acid (AA) was then absorbed on the nanosystem as a H₂O₂ prodrug and, meanwhile, was used for the regeneration of Fentons reagent for Fe²⁺. Finally, poly(ethylene glycol) (PEG) was coated on FeOCl@H-DMOS-AA to enhance the permeability and retention (EPR) effect in tumor tissue. The as-fabricated FeOCl@H-DMOS-AA/PEG can generate a large amount of highly toxic hydroxyl radicals (^•OH) by catalyzing H₂O₂ even in neutral pH conditions with the help of AA. As a result, the effect of CDT has been markedly enhanced by the increased amount of H₂O₂ and the efficient Fenton reaction in mild acidic TME, which can remove almost all of the tumors in mice. In addition, FeOCl also endows the nanosystem with T₂-weighted MR imaging capability (r₂ = 34.08 mM^-1 s^-1), thus realizing the imaging-guided cancer therapy. All in all, our study may contribute a new direction and may have a bright future for enhanced CDT with a neutral pH range.

A core-shell guanosine diphosphate crosslinked chitosan scaffold as a potential co-encapsulation platform

Recent engineering strategies to better mimic native tissue architecture involve co-encapsulation of cell lineages and/or growth factors in multi-compartmental scaffolds. This study introduces a core-shell platform based on a rapidly gelling guanosine diphosphate cross-linked chitosan scaffold for co-culture. The core-shell sponge is fabricated through combination of chitosan and guanosine diphosphate in 3 steps with each shell layer deposited around the previous layer. Co-encapsulation of pre-osteoblastic MC-3T3 cells and growth factors in the core-shell sponge showed similar microstructure to the standard sponge with high pore connectivity and low closed porosity (<0.4 %). A viable cell population was maintained over time with enhanced cellular functionality when ascorbic acid was added in the same compartment. Co-culture was explored with a proof-of-concept study shown for MC-3T3 and endothelial cells showing homogeneous distribution of cells in their intended compartment. Overall, this core-shell scaffold shows potential as a platform for the regeneration of multiple tissues.

A Promising Electrochemical Platform for Dopamine and Uric Acid Detection Based on a Polyaniline/Iron Oxide-Tin Oxide/Reduced Graphene Oxide Ternary Composite

A ternary polyaniline/Fe₂O₃-SnO₂/reduced graphene oxide (PFSG) nanocomposite was prepared using a simple two-step hydrothermal treatment. The composite was applied as a glassy carbon electrode modifier (GCE) to enhance dopamine (DA) and uric acid (UA) detection. The ternary PFSG composite was compared with its binary precursor Fe₂O₃-SnO₂/reduced graphene oxide (FSG). The influence of the modified GCE electrodes on their performance as a sensing platform was determined. GCE/PFSG showed better sensing parameters than GCE/FSG due to the introduction of polyaniline (PANI), increasing the electrocatalytic properties of the electrode towards the detected analytes. GCE/PFSG enabled the detection of low concentrations of DA (0.076 µM) and UA (1.6 µM). The peak potential separation between DA and UA was very good (180 mV). Moreover, the DA oxidation peak was unaffected even if the concentration of UA was ten times higher. The fabricated sensor showed excellent performance in the simultaneous detection with DA and UA limits of detection: LOD_DA = 0.15 µM and LOD_UA = 6.4 µM, and outstanding long-term stability towards DA and UA, holding 100% and 90% of their initial signals respectively, after one month of use.

Strawberry Puree Functionalized with Natural Hydroxytyrosol: Effects on Vitamin C and Antioxidant Activity

The natural antioxidant hydroxytyrosol (HT) was used to functionalize a strawberry puree. The effect of the antioxidant on the stability of the two bioactive forms of vitamin C (ascorbic acid-AA and dehydroascorbic acid-DHAA) in strawberry puree stored at 4 °C, compared with the effect on a model system of AA in water, was investigated. In the absence of HT, the concentration of vitamin C in strawberry puree decreased but not in the model system. Low concentrations of HT in strawberry puree (0.05 and 0.1 mg HT/g puree) stabilized vitamin C and improved its antioxidant activity. However, at high concentrations of HT (from 0.5 mg HT/g puree), although the antioxidant activity improved, degradation of vitamin C occurred. Therefore, the concentration of HT used to obtain a functionalized strawberry puree it is very important. An adequate concentration increases the antioxidant activity and protects vitamin C from degradation, developing a functional food. However, an inadequate concentration of HT affects the vitamin C content, which is essential for the human diet because it cannot be biosynthetized by the organism.

The Effect of Fermentation with Kefir Grains on the Physicochemical and Antioxidant Properties of Beverages from Blue Lupin (Lupinus angustifolius L.) Seeds

Plant derived fermented beverages have recently gained consumers' interest, particularly due to their intrinsic functional properties and presence of beneficial microorganisms. Three variants containing 5%, 10%, and 15% (w/w) of sweet blue lupin (Lupinus angustifolius L. cv. "Boregine") seeds were inoculated with kefir grains and incubated at 25 °C for 24 h. After processing, beverages were stored in refrigerated conditions (6 °C) for 21 days. Changes in microbial population, pH, bioactive compounds (polyphenolics, flavonoids, ascorbic acid), reducing sugars, and free amino acids were estimated. Additionally, viscosity, firmness, color, and free radicals scavenging properties were determined. Results showed that lactic acid bacteria as well as yeast were capable of growing well in the lupin matrix without any supplementation. During the process of refrigeration, the viability of the microorganisms was over the recommended minimum level for kefir products. Hydrolysis of polysaccharides as well as increase of free amino acids was observed. As a result of fermentation, the beverages showed excellent DPPH, ABTS+·, ·OH, and O2- radicals scavenging activities with a potential when considering diseases associated with oxidative stress. This beverages could be used as a new, non-dairy vehicle for beneficial microflora consumption, especially by vegans and lactose-intolerant consumers.

Carboxymethyl cellulose coating delays chilling injury development and maintains eating quality of 'Kinnow' mandarin fruits during low temperature storage

The application of edible coatings is an efficient way to reduce mass loss and to conserve the quality of a coated fresh produce during postharvest storage. In the present research, the impact of carboxymethyl cellulose [CMC (1%] coating was studied on 'Kinnow' mandarins during cold storage at 5 ± 1 °C for 30 days. Results showed that CMC treatment substantially suppressed chilling injury symptoms, disease incidence, fresh weight loss, malondialdehyde content, hydrogen peroxide and electrolyte leakage compared with control. The CMC coated 'Kinnow' mandarins showed markedly higher ascorbate peroxidase, peroxidase, superoxide dismutase and catalase enzyme activities compared to control. The treatment of 'Kinnow' mandarins with CMC also suppressed the increase in total soluble solids, ripening index and showed substantially higher titratable acidity, ascorbic acid, total phenolics content, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity along with better sensory quality in contrast with uncoated fruits. In conclusion, CMC coating could be an effective approach for the chilling injury reduction and quality maintenance of harvested 'Kinnow' mandarin fruits during cold storage.

The application of pharmaceutical quality by design concepts to evaluate the antioxidant and antimicrobial properties of a preservative system including desferrioxamine

BACKGROUND

The purpose of the present study was to investigate the antioxidant and antimicrobial activities of a conventional preservative system containing desferrioxamine mesylate (DFO) and optimize the composition of the system through mathematical models.

METHODS

Different combinations of ethylenediaminetetraacetic acid (EDTA), sodium metabisulfite (SM), DFO and methylparaben (MP) were prepared using factorial design of experiments. The systems were added to ascorbic acid (AA) solution and the AA content over time, at room temperature and at 40 °C was determined by volumetric assay. The systems were also evaluated for antioxidant activity by a fluorescence-based assay. Antimicrobial activity was assessed by microdilution technique and photometric detection against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus brasiliensis. A multi-criteria decision approach was adopted to optimize all responses by desirability functions.

RESULTS

DFO did not extend the stability of AA over time, but displayed a better ability than EDTA to block the pro-oxidant activity of iron. DFO had a positive interaction with MP in microbial growth inhibition. The mathematical models showed adequate capacity to predict the responses. Statistical optimization aiming to meet the quality specifications of the ascorbic acid solution indicated that the presence of DFO in the composition allows to decrease the concentrations of EDTA, SM and MP.

CONCLUSION

DFO was much more effective than EDTA in preventing iron-catalyzed oxidation. In addition, DFO improved the inhibitory response of most microorganisms tested. The Quality by Design concepts aided in predicting an optimized preservative system with reduced levels of conventional antioxidants and preservatives, suggesting DFO as a candidate for multifunctional excipient.