Showing papers on "Dehydroascorbic acid published in 2020"

Redox Interactions of Vitamin C and Iron: Inhibition of the Pro-Oxidant Activity by Deferiprone.

Abstract: Ascorbic acid (AscH2) is one of the most important vitamins found in the human diet, with many biological functions including antioxidant, chelating, and coenzyme activities. Ascorbic acid is also widely used in medical practice especially for increasing iron absorption and as an adjuvant therapeutic in iron chelation therapy, but its mode of action and implications in iron metabolism and toxicity are not yet clear. In this study, we used UV–Vis spectrophotometry, NMR spectroscopy, and EPR spin trapping spectroscopy to investigate the antioxidant/pro-oxidant effects of ascorbic acid in reactions involving iron and the iron chelator deferiprone (L1). The experiments were carried out in a weak acidic (pH from 3 to 5) and neutral (pH 7.4) medium. Ascorbic acid exhibits predominantly pro-oxidant activity by reducing Fe3+ to Fe2+, followed by the formation of dehydroascorbic acid. As a result, ascorbic acid accelerates the redox cycle Fe3+ ↔ Fe2+ in the Fenton reaction, which leads to a significant increase in the yield of toxic hydroxyl radicals. The analysis of the experimental data suggests that despite a much lower stability constant of the iron–ascorbate complex compared to the FeL13 complex, ascorbic acid at high concentrations is able to substitute L1 in the FeL13 chelate complex resulting in the formation of mixed L12AscFe complex. This mixed chelate complex is redox stable at neutral pH = 7.4, but decomposes at pH = 4–5 during several minutes at sub-millimolar concentrations of ascorbic acid. The proposed mechanisms play a significant role in understanding the mechanism of action, pharmacological, therapeutic, and toxic effects of the interaction of ascorbic acid, iron, and L1.

Exogenous application of melatonin maintains storage quality of jujubes by enhancing anti-oxidative ability and suppressing the activity of cell wall-degrading enzymes

Abstract: Jujube fruit was treated with melatonin to evaluate the changes of quality parameters, anti-oxidative ability and cell wall-degrading enzymes activities during room temperature storage. The results showed that melatonin treatment significantly inhibited respiratory rate and ethylene release of jujubes. Melatonin treatment also delayed the changes of color and sustained titratable acidity. Moreover, melatonin treatment increased the activities of glutathione reductase, ascorbate peroxidase and monodehydroascorbate reductase, and enhanced ascorbic acid, dehydroascorbic acid and reduced glutathione contents in jujubes. In addition, application of melatonin delayed fruit softening by inhibiting the activities of pectin methylesterase, polygalacturonase, cellulose and β-glucosidase and production of water soluble pectin and maintaining water insoluble pectin content. All these results indicate that application of melatonin after harvest could delay fruit softening, improve anti-oxidative capacity, and thus delay fruit senescence of jujubes.

Vitamin C controls neuronal necroptosis under oxidative stress

Abstract: Under physiological conditions, vitamin C is the main antioxidant found in the central nervous system and is found in two states: reduced as ascorbic acid (AA) and oxidized as dehydroascorbic acid (DHA). However, under pathophysiological conditions, AA is oxidized to DHA. The oxidation of AA and subsequent production of DHA in neurons are associated with a decrease in GSH concentrations, alterations in glucose metabolism and neuronal death. To date, the endogenous molecules that act as intrinsic regulators of neuronal necroptosis under conditions of oxidative stress are unknown. Here, we show that treatment with AA regulates the expression of pro- and antiapoptotic genes. Vitamin C also regulates the expression of RIPK1/MLKL, whereas the oxidation of AA in neurons induces morphological alterations consistent with necroptosis and MLKL activation. The activation of necroptosis by AA oxidation in neurons results in bubble formation, loss of membrane integrity, and ultimately, cellular explosion. These data suggest that necroptosis is a target for cell death induced by vitamin C.

Comparison of Effects of Potassium Iodide and Iodosalicylates on the Antioxidant Potential and Iodine Accumulation in Young Tomato Plants

Abstract: Iodine (I) is classified as a beneficial element for plants. Until now, there have been only hypotheses regarding the uptakes of organic iodine compounds by plant roots. The purpose of our research was to compare the uptakes and effects of the application of the following mineral and organic iodine compounds on young tomato plants: KI, 5-iodosalicylic (5-ISA), and 3,5-diiodosalicylic (3,5-diISA) acids. An additional control combination included the treatment with salicylic acid (SA) alone. All compounds were introduced into the nutrient solution in 5, 10, 25, and 50 μM I concentrations. It was established that after the application of 5-ISA and 3,5-diISA, iodine is taken up to a smaller extent than from KI. The tested KI, 3,5-diISA, and 5-ISA doses had no negative impact on the growth and development of plants, apart from the reduction of shoot biomass after the application of 3,5-diISA in 10 and 25 µM I doses. All applied compounds, except for SA, caused a reduction of ascorbic acid (AA) content and increase of dehydroascorbic acid (DHA) content in leaves. A significant increase of APX activity was noted only for the highest doses of KI and 5-ISA. None of the iodine compounds, in most tested doses, have substantially increased the CAT and POX activities in tomato leaves. Application of KI decreased the levels of all analyzed sugars in tomato leaves. The effect of iodosalicylates on sugar content varied depending on the compound: when applied in the highest dose 5-ISA increased, while 3,5-diISA decreased the sugar accumulation in tomato plants. In all tested treatments, a reduction of SA content in leaves was noted. We conclude that organic iodine compounds, i.e., 3,5-diISA and 5-ISA, can be taken up by the roots of tomato plants at an early stage of development.

A Novel and Potentially Multifaceted Dehydroascorbate Reductase Increasing the Antioxidant Systems is Induced by Beauvericin in Tomato

Abstract: Dehydroascorbate reductases (DHARs) are important enzymes that reconvert the dehydroascorbic acid (DHA) into ascorbic acid (ASC). They are involved in the plant response to oxidative stress, such as that induced by the mycotoxin beauvericin (BEA). Tomato plants were treated with 50 µM of BEA; the main antioxidant compounds and enzymes were evaluated. DHARs were analyzed in the presence of different electron donors by native and denaturing electrophoresis as well as by western blot and mass spectrometry to identify a novel induced protein with DHAR activity. Kinetic parameters for dehydroascorbate (DHA) and glutathione (GSH) were also determined. The novel DHAR was induced after BEA treatment. It was GSH-dependent and possessed lower affinity to DHA and GSH than the classical DHARs. Interestingly, the mass spectrometry analysis of the main band appearing on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) revealed a chloroplast sedoheptulose 1,7-bisphosphatase, a key enzyme of the Calvin cycle, and a chloroplast mRNA-binding protein, suggesting that the DHA reducing capacity could be a side activity or the novel DHAR could be part of a protein complex. These results shed new light on the ascorbate-glutathione regulation network under oxidative stress and may represent a new way to increase the plant antioxidant defense system, plant nutraceutical value, and the health benefits of plant consumption.

Determination of Ascorbic Acid, Total Ascorbic Acid, and Dehydroascorbic Acid in Bee Pollen Using Hydrophilic Interaction Liquid Chromatography-Ultraviolet Detection.

Abstract: Ascorbic acid (AA) is one of the essential nutrients in bee pollen, however, it is unstable and likely to be oxidized. Generally, the oxidation form (dehydroascorbic acid (DHA)) is considered to have equivalent biological activity as the reduction form. Thus, determination of the total content of AA and DHA would be more accurate for the nutritional analysis of bee pollen. Here we present a simple, sensitive, and reliable method for the determination of AA, total ascorbic acids (TAA), and DHA in rape (Brassica campestris), lotus (Nelumbo nucifera), and camellia (Camellia japonica) bee pollen, which is based on ultrasonic extraction in metaphosphoric acid solution, and analysis using hydrophilic interaction liquid chromatography (HILIC)-ultraviolet detection. Analytical performance of the method was evaluated and validated, then the proposed method was successfully applied in twenty-one bee pollen samples. Results indicated that contents of AA were in the range of 17.54 to 94.01 µg/g, 66.01 to 111.66 µg/g, and 90.04 to 313.02 µg/g for rape, lotus, and camellia bee pollen, respectively. In addition, percentages of DHA in TAA showed good intra-species consistency, with values of 13.7%, 16.5%, and 7.6% in rape, lotus, and camellia bee pollen, respectively. This is the first report on the discriminative determination between AA and DHA in bee pollen matrices. The proposed method would be valuable for the nutritional analysis of bee pollen.

Ascorbate Oxidase Induces Systemic Resistance in Sugar Beet Against Cyst Nematode Heterodera schachtii

Abstract: Ascorbate oxidase (AO) is an enzyme involved in catalyzing the oxidation of apoplastic ascorbic acid (AA) to dehydroascorbic acid (DHA). In this research, the potential of AO spraying to induce systemic resistance was demonstrated in the interaction between sugar beet root and cyst nematode Heterodera schachtii and the mechanism was elucidated. Plant bioassays showed that roots of AO-sprayed plants were infested by a significantly lower number of females and cysts when compared with mock-sprayed control plants. Hormone measurements showed an elevated level of jasmonic acid (JA) salicylic acid (SA) and ethylene (ET) in the roots of AO-sprayed plants, with a dynamic temporal pattern of activation. Experiments with chemical inhibitors showed that AO-induced systemic resistance is partially dependent on the JA, ET and SA pathways. Biochemical analyses revealed a primed accumulation of hydrogen peroxide (H2O2), and phenylalanine ammonia lyase (PAL) activity in the roots of AO-sprayed plants upon infection by cyst nematodes. In conclusion, our data shows that AO works as an effective systemic defense priming agent in sugar beet against cyst nematode infection, through activation of multiple basal plant defense pathways.

Erythroid glucose transport in health and disease

Abstract: Glucose transport is intimately linked to red blood cell physiology. Glucose is the unique energy source for these cells, and defects in glucose metabolism or transport activity are associated with impaired red blood cell morphology and deformability leading to reduced lifespan. In vertebrate erythrocytes, glucose transport is mediated by GLUT1 (in humans) or GLUT4 transporters. These proteins also account for dehydroascorbic acid (DHA) transport through erythrocyte membrane. The peculiarities of glucose transporters and the red blood cell pathologies involving GLUT1 are summarized in the present review.

Dehydroascorbic Acid Affects the Stability of Catechins by Forming Conjunctions.

Abstract: Although tea catechins in green tea and green tea beverages must be stable to deliver good sensory quality and healthy benefits, they are always unstable during processing and storage. Ascorbic acid (AA) is often used to protect catechins in green tea beverages, and AA is easily oxidized to form dehydroascorbic acid (DHAA). However, the function of DHAA on the stability of catechins is not clear. The objective of this study was to determine the effects of DHAA on the stability of catechins and clarify the mechanism of effects by conducting a series of experiments that incubate DHAA with epigallocatechin gallate (EGCG) or catechins. Results showed that DHAA had a dual function on EGCG stability, protecting its stability by inhibiting hydrolysis and promoting EGCG consumption by forming ascorbyl adducts. DHAA also reacted with (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin (EGC) to form ascorbyl adducts, which destabilized them. After 9 h of reaction with DHAA, the depletion rates of EGCG, ECG, EC, and EGC were 30.08%, 22.78%, 21.45%, and 13.55%, respectively. The ability of DHAA to promote catechins depletion went from high to low: EGCG, ECG, EGC, and EC. The results are important for the processing and storage of tea and tea beverages, as well as the general exploration of synergistic functions of AA and catechins.

Development and validation of a differential pulse polarography method for determination of total vitamin C and dehydroascorbic acid contents in foods

Abstract: The objective of the study was to develop a new method for the determination of total vitamin C and dehydroascorbic acid contents in food using the differential pulse polarography technique, and to compare achieved results to those obtained with the proposed reference method applying HPLC with spectrophotometric detection. Dithiothreitol was used to reduce dehydroascorbic acid into l -ascorbic acid. Interference due to the presence of dithiothreitol during polarographic determination of l -ascorbic acid was efficiently eliminated by clarification of the sample solution with Carrez reagent. Validation of the polarographic method indicates its usefulness for the analysis of foods products that do not contain isoascorbic acid. The coefficient of variation for the analysis of l -ascorbic acid and total vitamin C content ranges from 1.86% to 6.98%, Horrat values from 0.41 to 0.89 and average recovery of l -ascorbic acid ranges from 98% to 104%. Results obtained using the developed method are characterised by high compatibility with those obtained with the HPLC reference method, indicating equivalence of both methods, and in conclusion, the method was deemed fit for purpose for measuring total vitamin C and dehydroascorbic acid in foods.

Glutathione and Glutathione-Like Sequences of Opioid and Aminergic Receptors Bind Ascorbic Acid, Adrenergic and Opioid Drugs Mediating Antioxidant Function: Relevance for Anesthesia and Abuse.

Abstract: Opioids and their antagonists alter vitamin C metabolism. Morphine binds to glutathione (l-γ-glutamyl-l-cysteinyl-glycine), an intracellular ascorbic acid recycling molecule with a wide range of additional activities. The morphine metabolite morphinone reacts with glutathione to form a covalent adduct that is then excreted in urine. Morphine also binds to adrenergic and histaminergic receptors in their extracellular loop regions, enhancing aminergic agonist activity. The first and second extracellular loops of adrenergic and histaminergic receptors are, like glutathione, characterized by the presence of cysteines and/or methionines, and recycle ascorbic acid with similar efficiency. Conversely, adrenergic drugs bind to extracellular loops of opioid receptors, enhancing their activity. These observations suggest functional interactions among opioids and amines, their receptors, and glutathione. We therefore explored the relative binding affinities of ascorbic acid, dehydroascorbic acid, opioid and adrenergic compounds, as well as various control compounds, to glutathione and glutathione-like peptides derived from the extracellular loop regions of the human beta 2-adrenergic, dopamine D1, histamine H1, and mu opioid receptors, as well as controls. Some cysteine-containing peptides derived from these receptors do bind ascorbic acid and/or dehydroascorbic acid and the same peptides generally bind opioid compounds. Glutathione binds not only morphine but also naloxone, methadone, and methionine enkephalin. Some adrenergic drugs also bind to glutathione and glutathione-like receptor regions. These sets of interactions provide a novel basis for understanding some ways that adrenergic, opioid and antioxidant systems interact during anesthesia and drug abuse and may have utility for understanding drug interactions.

Improved UPLC-UV Method for the Quantification of Vitamin C in Lettuce Varieties (Lactuca sativa L.) and Crop Wild Relatives (Lactuca spp.)

Abstract: Vitamins, especially vitamin C, are important micronutrients found in fruits and vegetables. Vitamin C is also a major contributor to their antioxidant capacity. Lettuce is one of the most popular vegetables among consumers worldwide. An accurate protocol to measure vitamin C content in lettuce and other related species is crucial. We describe here a method using the ultra-high-performance liquid chromatography-ultraviolet (UPLC-UV) technique, in which sample preparation, vitamin extraction and chromatography conditions were optimized. Samples were collected to represent the entire plant, frozen at -80 °C and lyophilized to prevent undesirable oxidation and make their manipulation easier. The extraction of vitamin C was carried out in acidic media, which also contributed to its stability. As vitamin C can be present in two different interconvertible forms, ascorbic acid (AA) and dehydroascorbic acid (DHAA), both compounds should be measured for accurate quantification. The DHAA was quantified indirectly after its reduction to AA because AA shows a higher absorptivity than DHAA in the UV range of the spectrum. From the same extract, two measurements were carried out, one before and one after that reduction reaction. In the first case, we were quantifying the AA content, and in the second one, we quantified the sum of AA and DHAA (TAA: total ascorbic acid) in the form of AA. Then, DHAA quantity was indirectly obtained by subtracting AA coming from the first measurement from TAA. They were determined by UPLC-UV, using a commercial AA standard to build a calibration curve and optimizing the chromatographic procedure, to obtain AA peaks that were completely resolved in a short time. This protocol could be easily extrapolated to any other plant material with slight or no changes. Its accuracy revealed statistically significant differences otherwise unperceived. Other strengths and limitations are discussed more in depth in the manuscript.

Vitamin C Recycling Regulates Neurite Growth in Neurospheres Differentiated In Vitro.

Abstract: The reduced form of vitamin C, ascorbic acid (AA), has been related with gene expression and cell differentiation in the cerebral cortex. In neurons, AA is mainly oxidized to dehydroascorbic acid (DHA); however, DHA cannot accumulate intracellularly because it induces metabolic changes and cell death. In this context, it has been proposed that vitamin C recycling via neuron–astrocyte coupling maintains AA levels and prevents DHA parenchymal accumulation. To date, the role of this mechanism during the outgrowth of neurites is unknown. To stimulate neuronal differentiation, adhered neurospheres treated with AA and retinoic acid (RA) were used. Neuritic growth was analyzed by confocal microscopy, and the effect of vitamin C recycling (bystander effect) in vitro was studied using different cells. AA stimulates neuritic growth more efficiently than RA. However, AA is oxidized to DHA in long incubation periods, generating a loss in the formation of neurites. Surprisingly, neurite growth is maintained over time following co-incubation of neurospheres with cells that efficiently capture DHA. In this sense, astrocytes have high capacity to recycle DHA and stimulate the maintenance of neurites. We demonstrated that vitamin C recycling in vitro regulates the morphology of immature neurons during the differentiation and maturation processes.

Comprehensive and quantitative stability study of ascorbic acid using capillary zone electrophoresis with ultraviolet detection and high resolution tandem mass spectrometry

Abstract: Ascorbic acid is a powerful antioxidant compound involved in many biological functions, and a chronic deficiency is at the origin of scurvy disease. A simple, rapid, and cost-effective capillary electrophoresis method was developed for the separation and simultaneous quantification of ascorbic acid and the major degradation products: dehydroascorbic acid, furfural, and furoic acid. Systematic optimization of the conditions was performed that enabled baseline separation of the compounds in less than 10 min. In addition to simultaneous quantification of ascorbic acid alongside to the degradation products, stability studies demonstrated the possibility using capillary electrophoresis to separate and identify the major degradation products. Thus, high-resolution tandem mass spectrometry experiments were conducted in order to identify an unknown degradation product separated by capillary electrophoresis and significantly present in degraded samples. Comparison of mass spectrometry data and capillary electrophoresis electropherograms allowed to identify unambiguously trihydroxy-keto-valeraldehyde. Finally, capillary electrophoresis was successfully applied to evaluate the composition of different pharmaceutical preparation of ascorbic acid. Results showed the excellent performance of the capillary electrophoresis method due to the separation of excipients from the compounds of interest, which demonstrated the relevance of using an electrophoretic separation in order to perform comprehensive stability studies of ascorbic acid.

Ascorbate in the Apoplast: Metabolism and Functions

Abstract: Ascorbic acid (AA) is one of the most important antioxidants and redox-active substances of plants found in the apoplast. In the form of ascorbate anion, it can be exported to the cell wall through anion channels, where it is further oxidized to dehydroascorbic acid (DHA) and in this form is translocated back into the cytoplasm through as yet unidentified transporters. In the apoplast AA is exposed to both enzymatic and non-enzymatic oxidation, participating in the antioxidant and pro-oxidant processes: detoxification of O3, generation of hydroxyl radicals, reduction of phenoxyl radicals, etc. The intermediate product of the AA oxidation in apoplast, monodehydroascorbic acid (MDHA), serves as an extracellular electron acceptor for a number of redox chains localized at the plasma membrane (PM). All three forms of ascorbate, AA, DHA and MDHA, can potentially be involved in the cell signalling. Released from the cell through anionic channels during PM depolarization, AA can stimulate the production of hydroxyl radicals that activate Ca2+-permeable channels, and thus trigger Ca2+-signalling. Due to the ability to generate hydroxyl radicals and reduce phenoxyl radicals, AA affects cell wall extensibility and extension growth. By reducing Fe3+ to a freely soluble transport form of Fe2+, AA is involved in iron uptake by root cells. Apoplastic AA also plays an important role in a number of other processes and is potentially a unique signal-regulatory molecule functioning in the plant cell walls.

Dehydroascorbic acid, the oxidized form of vitamin C, improves renal histology and function in old mice

Abstract: Oxidative stress and inflammation are crucial factors that increase with age. In the progression of multiple age-related diseases, antioxidants and bioactive compounds have been recognized as useful antiaging agents. Oxidized or reduced vitamin C exerts different actions on tissues and has different metabolism and uptake. In this study, we analyzed the antiaging effect of vitamin C, both oxidized and reduced forms, in renal aging using laser microdissection, quantitative reverse-transcription polymerase chain reaction, and immunohistochemical analyses. In the kidneys of old SAM mice (10 months of age), a model of accelerated senescence, vitamin C, especially in the oxidized form (dehydroascorbic acid [DHA]) improves renal histology and function. Serum creatinine levels and microalbuminuria also decrease after treatment with a decline in azotemia. In addition, sodium-vitamin C cotransporter isoform 1 levels, which were increased during aging, are normalized. In contrast, the pattern of glucose transporter 1 expression is not affected by aging or vitamin C treatment. We conclude that oxidized and reduced vitamin C are potent antiaging therapies and that DHA reverses the kidney damage observed in senescence-accelerated prone mouse 8 to a greater degree.

Erythrocyte Ascorbate Is a Potential Indicator of Steady-State Plasma Ascorbate Concentrations in Healthy Non-Fasting Individuals.

Abstract: Plasma vitamin C concentrations fluctuate in response to recent dietary intake; therefore levels are typically determined in the fasting state. Erythrocyte ascorbate concentrations have been shown to be similar to plasma levels, but little is known about the kinetics of ascorbate accumulation in these cells. In this study, we investigated ascorbate uptake into erythrocytes after dietary supplementation with vitamin C and compared it to changes in plasma ascorbate concentrations. Seven individuals with baseline fasting plasma vitamin C concentrations ≥ 50 µmol/L were depleted of vitamin C-containing foods and drinks for one week, and then supplemented with 250 mg vitamin C/day in addition to resuming their normal diet. Fasting or steady-state plasma ascorbate concentrations declined to almost half of their baseline concentration over the week of vitamin C depletion, and then returned to saturation within two days of beginning supplementation. Erythrocyte ascorbate concentrations exhibited a very similar profile to plasma levels, with values ~76% of plasma, and a strong linear correlation (r = 0.89, p < 0.0001). Using a pharmacokinetic study design in six individuals with baseline fasting plasma vitamin C concentrations ≥50 µmol/L, we also showed that, unlike plasma, which peaked between 2 and 4 h following ingestion of 200 mg of vitamin C, erythrocyte ascorbate concentrations did not change in the six hours after supplementation. The data from these two intervention studies indicate that erythrocyte ascorbate concentration provides a stable measure of steady-state plasma ascorbate status and could be used to monitor ascorbate status in healthy non-fasting individuals.

Resveratrol potentiates intracellular ascorbic acid enrichment through dehydroascorbic acid transport and/or its intracellular reduction in HaCaT cells

Abstract: L-Ascorbic acid (AsA), a reduced vitamin C (VC), is an important antioxidant, and the internal accumulation and maintenance of AsA are thought to play a significant role in various physiological activities in humans. We focused on resveratrol (RSV), a natural polyphenolic compound, as a candidate for an AsA transport modulator and investigated whether RSV can affect the intracellular VC accumulation after either AsA or dehydroascorbic acid (DHA) addition in HaCaT keratinocytes. Our results demonstrate that RSV treatment could significantly enhance intracellular VC levels after either AsA or DHA supplementation, and intracellular VC accumulated mainly as AsA. Our results also indicate that most of the intracellular transported DHA was reduced to AsA and accumulated after uptake into cells. In addition, RSV could induce several AsA or DHA transport-related and intracellular DHA reduction-related genes including SVCT2, GLUT3, TXNRD2, and TXNRD3, necessary for AsA transport, DHA transport, and DHA reduction/regeneration, respectively. On the other hand, the both protein expression levels and the localizations of sodium-dependent vitamin C transporters 2 (SVCT2) and glucose transporter 3(GLUT3) were scarcely affected by RSV treatment. Furthermore, RSV-induced enrichment of intracellular AsA levels was completely suppressed by a GLUT inhibitor cytochalasin B. These results suggest that RSV can potentiate intracellular AsA accumulation via activation of the DHA transport and subsequent intracellular reduction from DHA to AsA. Thus, RSV might be useful for maintaining substantial AsA accumulation in the skin keratinocytes.

Electrochemical detection of vitamin C in real samples.

Abstract: Electrochemical properties of vitamin C (also known as L-ascorbic acid) have been studied by cyclic and differential pulse voltammetry in the model systems in order to develop simple and suitable method for vitamin C detection in real samples. The results indicated that vitamin C oxidation is a quasi-reversible and diffusion-controlled process, as well that the oxidation product of ascorbic acid, dehydroascorbic acid is adsorbed on the glassy carbon electrode surface. Calibration curve was constructed and the linear response was obtained in a concentration range from 0.0025 mol dm -3 to 1.0 mol dm -3 . Vitamin C was successfully determined in real samples (fruit juices and food supplement) with cyclic voltammetry within concentration range from 0.034 mol dm -3 to 0.340 mol dm -3 . In addition, antioxidant activity of vitamin C in real samples was determined using DPPH assay with a good linear correlation obtained between the cyclic voltammetry results and the results evaluated by DPPH assay of the samples.

Physiological response of ‘Italia’ grapevine to some “Esca complex”-associated fungi

Abstract: This study investigated some physiological features in a 20-year-old ‘Italia’ vineyard cropped in Apulia, Italy. Five vines with brown-wood-streaking associated to Phaeoacremonium minimum (sin. Pm. aleophilum) and Phaeomoniella chlamydospora (BWSV), five with brown-wood-streaking and white-rot caused by Fomitiporia mediterranea (BWSWRV) and five healthy vines (HV) were surveyed. Bleeding xylem sap (BXS) collected at bud-break, symptomless and symptomatic leaves taken during stretched-out leaves, fruit setting, cluster closing and bunch ripening phenological phases were characterized. BXS from HV showed the highest total ascorbic acid level, while BWSWRV had the highest viscosity coefficient, glutathione concentration and growth regulators activity. Low fresh and dry weight, total chlorophyll concentration and the hight leaf surface, hydrogen peroxide and cell membranes damage were detected in leaves of diseased vines. Symptomless and symptomatic leaves of BWSV and BWSWRV exhibited low concentrations of ascorbic acid, reduced glutathione and redox state; moderate levels of dehydroascorbic acid and oxidized glutathione. Higher dehydroascorbate reductase and low ascorbate free radical reductase and glutathione reductase activities were showed by leaves collected from diseased vines. However, no differences were detected in ascorbate peroxidase activity. The decrease of oxidative status alters cell membranes integrity and could contribute to cell death and symptoms development on leaves.

Studies Concerning the Stability if Antioxidant Compounds in Aronia Melanocarpa Fruits

Abstract: Aronia Melanocarpa fruits are high in vitamin C. Vitamin C is an antioxidant necessary for the human body to prevent scurvy, gum disease, bone and blood vessels and boost immunity. The paper also highlighted the determination of vitamin C in the Aronia Melanocarpa fruits, and studies on the stability of vitamin C in different pH environments in the process of oxidation in atmospheric oxygen. Ascorbics acid oxidation reaction proceeds through a chained mechanism. In 1936 Barron et all. [1], conducted the first study of auto-oxidation of ascorbic acid to dehydroascorbic acid. Through this research, we highlight areas where vitamin C pH will be stable.

Prooxidant-antioxidant homeostasis in boars depending on the types of higher nervous activity

Abstract: The peculiarities of formation of prooxidant-antioxidant homeostasis (PAG) in boars of different types of higher nervous activity have been studied. Using motor-nutritional techniques, it has been opposed adult boars of the Large White breed aged 24–36 months according to the main types of higher nervous activity (HNA). Four groups of 3 heads each were formed. The first group includes animals of a strong balanced lively (mobile) type; group II includes a strong balanced calm (inert) type; group III includes a strong unbalanced (unrestrained) type; group IV includes a weak type of higher nervous activity. Sperm was received from boars manually, taking into account the total time of ejaculation, dividing the ejaculate into 4 fractions – F1 – the first, F2 – the second, F3 – the third, F4 – the fourth. PAGs in blood and ejaculates of boars were evaluated by the intensity of peroxidation processes (xanthine oxidase, diene conjugates, TBA-active compounds) and antioxidant defense systems (superoxide dismutase, catalase, reduced glutathione, ascorbic acid, vitamin A and vitamin E). Sperm contained higher amounts of diene conjugates and TBA-active complexes (P < 0.05) compared to blood. The second tissue relative to the first one is characterized by a higher level of antioxidant defense: catalase activity, concentration of ascorbic acid, vitamin A and vitamin E. The process of PAG formation in the tissues of boars depends on the type of higher nervous activity (HNA). Thus, in individuals of a strong balanced lively and calm type, the course of peroxidation processes is somewhat slower because of a lower concentration of diene conjugates and TBA-active complexes. It was determined the fact that in blood and sperm of boars of strong unbalanced and weak types of HNA the course of peroxidation is more intense, the antioxidant defense system is at a lower level that is connected with less superoxide dismutase activity (P < 0.05), concentration of ascorbic acid (P < 0.001), vitamin A (P < 0.01–0.001), and vitamin E (P < 0.001). In the second and third fractions of ejaculate of boars, the PAG is shifted in the direction of probable acceleration of peroxidation processes, especially in strong unbalanced and weak types of HNA because of a higher concentration of diene conjugates, dehydroascorbic acid. Animals of a strong balanced lively and calm types of HNA are characterized by a higher level of antioxidant defence – catalase activity, superoxide dismutase, reduced glutathione, ascorbic acid and vitamin E. In the first and fourth fractions of ejaculate, peroxidation processes are slower and there is no superoxide dismutase activity and the amount of vitamin A and vitamin E.

Vitamin C Alimentation via SLC Solute Carriers

Abstract: In humans, ascorbic acid is an essential vitamin, antioxidant, and cofactor of a variety of metal ion–dependent enzymatic reactions. In this review, the transport of L-ascorbic acid is described from food to target cells. Transport of ascorbic acid across the plasma membrane is facilitated by members of the SLC23 family, SLC23A1/SVCT1 and SLC23A2/SVCT2. We present in silico models of these transporters that provide new insights into the structure of the SLC23 family. While SVCT1 is mainly responsible for uptake of ascorbic acid from the intestine into the blood and for reabsorption in the kidney, the more broadly expressed transporter SVCT2 delivers ascorbic acid into tissues that are in high demand of the vitamin. The oxidized form of ascorbic acid, dehydroascorbic acid (DHA), is a substrate of the glucose transporters (GLUTs) belonging to the SLC2 family. They play important roles in ascorbic acid recycling, such as in the brain and in erythrocytes. Ascorbic acid serves as an essential cofactor of metal ion–dependent enzymes, keeping their metal ions in the reduced state. In addition, it serves as an effective antioxidant in cells with high metabolic activity such as neurons. Thus, it is not too surprising that changes in expression and function of the sodium-dependent vitamin C transporters (SVCTs) have nutritional and pathologic consequences such as during aging, malnutrition, and chronic alcohol abuse or in cancer, neurodegenerative diseases, and chronic inflammation diseases. In the future, SVCT1 and SVCT2 may furthermore prove useful as drug delivery systems, to enhance transport of novel pharmaceutical agents more efficiently across the intestinal epithelium and the blood–cerebrospinal fluid barrier.