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Sonovoltammetric behavior of ascorbic acid and dehydroascorbic acid at glassy carbon electrodes: Analysis using pulsed sonovoltammetry

Compton, Richard G.; Matysik, Frank-Michael
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.71%
The effect of power ultrasound on the voltammetric behavior of ascorbic acid and dehydroascorbic acid at a glassy carbon electrode is described. The voltammetric characteristics of both compounds were found to be modified by ultrasonically formed radicals. In the case of dehydroascorbic acid the single sweep voltammogram shows an anodic signal in the presence of ultrasound which probably results from the formation of an oxidizable radical known to be an intermediate of ascorbic acid oxidation. In the case of ascorbic acid pulsed sonovoltammetry is applied and characterized regarding the time dependence of the current decay and the reliability of its analytical performance. The utility of pulsed sonovoltammetry is demonstrated analyzing a pain killer tablet regarding the ascorbic acid content.; http://dx.doi.org/10.1002/elan.1140080304

α-Lipoic acid-enrichment partially reverses tissue ascorbic acid depletion in pacu (Piaractus mesopotamicus) fed vitamin C-devoid diets

Park, Kwan Ha; Terjesen, Bendik Fyhn; Tesser, Marcelo Borges; Portella, Maria Célia; Dabrowski, Konrad
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 329-338
ENG
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56.73%
Effects of dietary α-lipoic acid (LA) and ascorbic acid (AA) on the growth, tissue vitamin C and tocopherol (vitamin E) levels, and malondialdehyde levels were examined in the tropical fish pacu, Piaractus mesopotamicus. Pacu juveniles were fed one of four casein-gelatin-based diets for 8 weeks: with 0.05% AA and 0.1% LA (+AA+LA), with AA and without LA (+AA-LA), without AA and with LA (-AA+LA), and without AA and LA (-AA-LA). When the fish received quantities of feed equal to 1.9-2.5% of its body weight, growth was not influenced, regardless of the presence of AA or LA throughout most of the experimental period. Growth was, however, slightly but significantly lower at week 8 in the AA-deficient/LA-supplemented group. An AA-deficient diet caused a highly significant reduction in both total AA and dehydroascorbic acid content in the liver and gill tissues. This reduction of tissue AA concentrations was reversed in a significant manner by LA (antioxidant-sparing effect). The 8-week-long vitamin C deprivation was sufficient to initiate the reduction in tissue ascorbic acid; however, total ascorbate in the liver of fish in the (-)AA/(+)LA group was 127.7±54.3 nmol g-1 tissue, whereas it was 28.6±26.3 nmol g-1 in the (-)AA/(-)LA group...

Comparative study of six pear cultivars in terms of their phenolic and vitamin C contents and antioxidant capacity

Sánchez, Andrea C. Galvis; Gil-Izquierdo, Angel; Gil, Maria
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
Publicado em //2003 ENG
Relevância na Pesquisa
46.72%
The main phenolic compounds in six pear cultivars were identified and quantified using high-performance liquid chromatography/diode array detection (HPLC/DAD) and HPLC/electrospray ionisation mass spectrometry (HPLC/ESIMS). Major quantitative differences were found in the phenolic profiles. The peel contained higher concentrations of chlorogenic acid, flavonols and arbutin than the flesh, where only chlorogenic acid was detected. Total phenolics ranged from 1235 to 2005mgkg−1 in the peel and from 28 to 81mg k g−1 in the flesh. Ascorbic acid and dehydroascorbic acid were detected in the peel, whereas only dehydroascorbic acid was present in the flesh. The ranges of vitamin C content were from 116 to 228mg kg−1 in the peel and from 28 to 53mg kg−1 in the flesh. The antioxidant capacity was correlated with the content of chlorogenic acid (r = 0.46), while ascorbic acid made only a small contribution to the total antioxidant capacity of the fruit.

Modelling ascorbic acid thermal degradation and browning in orange juice under aerobic conditions

Manso, Maria C.; Oliveira, Fernanda A.R.; Oliveira, Jorge C.; Frías, Jesús M.
Fonte: Willey Blackwell Publicador: Willey Blackwell
Tipo: Artigo de Revista Científica
Publicado em //2001 ENG
Relevância na Pesquisa
56.5%
The thermal degradation of ascorbic acid (AA) in orange juice was analysed over in a 20–45 °C temperature range. Dehydroascorbic acid (DA), pH and browning were also monitored. Small amounts of AA degradation could be described by first order kinetics, but when only low amounts of AA were retained sigmoidal kinetics were clearly appropriate. The Weibull model was used to describe this pattern (R2adj > 0.995). The rate constant increased with temperature according to an Arrhenius-type relationship. The activation energy was 38.6 kJ/mol and at the average temperature of the range tested, 32.5 °C, the rate constant was 64.4 × 10−3 h−1. The shape constant decreased linearly with temperature, from 2.17 to 1.13. Before the time when the maximum degradation rate occurred, pH, DA concentration and browning remained fairly constant, and then increased. It was found that this behaviour, as well as the dependence of the shape constant on temperature, might be explained by (i) the reconversion of DA into AA, following first order kinetics in relation to DA and second order kinetics in relation to AA, and by (ii) different sensitivities of the reaction rate constants to temperature. Browning was also well described by the Weibull model with a temperature independent shape constant.

Mathematical modeling of the thermal degradation kinetics of vitamin C in cupuaçu (Theobroma grandiflorum) nectar

Vieira, Margarida C.; Teixeira, A. A.; Silva, C. L. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2000 ENG
Relevância na Pesquisa
46.5%
The thermal degradation kinetics of both components of vitamin C, ascorbic acid (AA) and dehydroascorbic acid (DHAA), were determined in a nectar of Cupuacßu (Theobroma grandi¯orum) with 25% of pulp and 15% of sugar in water. AA was assayed by HPLC and the results showed that AA degraded into DHAA. A reversible ®rst order model described well the AA degradation data, with an activation energy of 74 5 kJ/mol and k80 C 0:032 0:003min ÿ1. DHAA kinetic behavior suggested a consecutive ®rst order reaction where DHAA was the intermediate product of AA degradation. A mechanistic model was derived to predict DHAA concentration. Rate constants were replaced by the Arrhenius equation in the model to evaluate the temperature dependence and the kinetic parameters for AA degradation, previously determined, were used. An activation energy of 65 9 kJ/mol and a k80 C of 0:013 0:003 min ÿ1 were estimated. The present ®ndings will help to predict the best Cupuacßu nectar processing conditions that minimize degradation of an important quality factor such as vitamin C.

Dehydroascorbic acid, a blood–brain barrier transportable form of vitamin C, mediates potent cerebroprotection in experimental stroke

Huang, Judy; Agus, David B.; Winfree, Christopher J.; Kiss, Szilard; Mack, William J.; McTaggart, Ryan A.; Choudhri, Tanvir F.; Kim, Louis J; Mocco, J; Pinsky, David J.; Fox, William D.; Israel, Robert J.; Boyd, Thomas A.; Golde, David W.; Connolly, E. Sa
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 25/09/2001 EN
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46.47%
Neuronal injury in ischemic stroke is partly mediated by cytotoxic reactive oxygen species. Although the antioxidant ascorbic acid (AA) or vitamin C does not penetrate the blood–brain barrier (BBB), its oxidized form, dehydroascorbic acid (DHA), enters the brain by means of facilitative transport. We hypothesized that i.v. DHA would improve outcome after stroke because of its ability to cross the BBB and augment brain antioxidant levels. Reversible or permanent focal cerebral ischemia was created by intraluminal middle cerebral artery occlusion in mice treated with vehicle, AA, or DHA (40, 250, or 500 mg/kg), either before or after ischemia. Given before ischemia, DHA caused dose-dependent increases in postreperfusion cerebral blood flow, with reductions in neurological deficit and mortality. In reperfused cerebral ischemia, mean infarct volume was reduced from 53% and 59% in vehicle- and AA-treated animals, respectively, to 15% in 250 mg/kg DHA-treated animals (P < 0.05). Similar significant reductions occurred in nonreperfused cerebral ischemia. Delayed postischemic DHA administration after 15 min or 3 h also mediated improved outcomes. DHA (250 mg/kg or 500 mg/kg) administered at 3 h postischemia reduced infarct volume by 6- to 9-fold...

Vitamin C Is a Kinase Inhibitor: Dehydroascorbic Acid Inhibits IκBα Kinase β

Cárcamo, Juan M.; Pedraza, Alicia; Bórquez-Ojeda, Oriana; Zhang, Bing; Sanchez, Roberto; Golde, David W.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/2004 EN
Relevância na Pesquisa
46.47%
Reactive oxygen species (ROS) are key intermediates in cellular signal transduction pathways whose function may be counterbalanced by antioxidants. Acting as an antioxidant, ascorbic acid (AA) donates two electrons and becomes oxidized to dehydroascorbic acid (DHA). We discovered that DHA directly inhibits IκBα kinase β (IKKβ) and IKKα enzymatic activity in vitro, whereas AA did not have this effect. When cells were loaded with AA and induced to generate DHA by oxidative stress in cells expressing a constitutive active IKKβ, NF-κB activation was inhibited. Our results identify a dual molecular action of vitamin C in signal transduction and provide a direct linkage between the redox state of vitamin C and NF-κB signaling events. AA quenches ROS intermediates involved in the activation of NF-κB and is oxidized to DHA, which directly inhibits IKKβ and IKKα enzymatic activity. These findings define a function for vitamin C in signal transduction other than as an antioxidant and mechanistically illuminate how vitamin C down-modulates NF-κB signaling.

Transport of ascorbic acid and dehydroascorbic acid by pancreatic islet cells from neonatal rats.

Zhou, A; Nielsen, J H; Farver, O; Thorn, N A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/03/1991 EN
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46.89%
Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.

Purification, cloning and expression of dehydroascorbic acid-reducing activity from human neutrophils: identification as glutaredoxin.

Park, J B; Levine, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/05/1996 EN
Relevância na Pesquisa
47.02%
Dehydroascorbic acid-reducing activity in normal human neutrophil lysates was characterized and identified by activity-based purification and measurement of newly synthesized ascorbate by HPLC. The initial reducing activity was non-dialysable and could not be accounted for by the activity of glutathione as a reducing agent. The reducing activity was purified to homogeneity as an 11 kDa protein. The protein had a specific activity of 3 mumol/min per mg of protein and was glutathione dependent. Kinetic experiments showed that the protein had a K(m) for glutathione of 2.0 mM and a K(m) for dehydroascorbic acid of 250 microM. Dehydroascorbic acid reduction by the purified protein was pH dependent and was maximal at pH 7.5. Peptide fragments from the purified protein were analysed for amino acid sequence and the protein was identified as glutaredoxin. By using degenerate oligonucleotides based on the amino acid sequence, glutaredoxin was cloned from a human neutrophil library. Expressed purified glutaredoxin displayed reducing activity and kinetics that were indistinguishable from those of native purified enzyme. Several approaches indicated that glutaredoxin was responsible for the most of the protein-mediated dehydroascorbic acid reduction in lysates. From protein purification data...

Dehydroascorbic acid uptake in a human keratinocyte cell line (HaCaT) is glutathione-independent.

Savini, I; Duflot, S; Avigliano, L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/02/2000 EN
Relevância na Pesquisa
46.78%
Vitamin C plays an important role in neutralizing toxic free radicals formed during oxidative metabolism or UV exposure of human skin. This study was performed to investigate the mechanisms that regulate the homoeostasis of vitamin C in HaCaT cells by identifying the events involved in the transport and in the reduction of dehydroascorbic acid. Dehydroascorbic acid accumulated to a greater extent and faster compared with ascorbic acid; its transport appeared to be mediated by hexose transporters and was entirely distinct from ascorbic acid transport. Dehydroascorbate reductase activity was unaffected by glutathione depletion, although it was sensitive to thiol protein reagents. These observations, as well as the subcellular distribution of this enzymic activity and the cofactor specificity, indicate that thioredoxin reductase and lipoamide dehydrogenase play an important role in this reduction process. HaCaT cells were able to enhance their dehydroascorbic acid reductase activity in response to oxidative stress.

Ascorbic acid and dehydroascorbic acid in HeLa cells: their effect on the collagen-peptidase activity of glucose-deficient cultures.

Boggust, W. A.; McGauley, H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1978 EN
Relevância na Pesquisa
46.56%
HeLa cells in culture do not accumulate ascorbic acid unless ascorbic acid or dehydroascorbic acid is available in the medium. Collagen peptidase corresponding to the activity found in the invasive zone of tumours, and acid phosphatase, in HeLa cells cultured under normal conditions, are unaffected by ascorbic acid, but are reduced in cells deprived of carbohydrate. These reduced collagen-peptidase levels, but not acid phosphatase, are restored to the values of normal HeLa cells by ascorbic acid. The relevance of these findings is considered in the context of tumour growth and spread.

Antiviral effects of dehydroascorbic acid

UOZAKI, MISAO; IKEDA, KEIKO; TSUJIMOTO, KAZUKO; NISHIDE, MITSUNORI; YAMASAKI, HISASHI; KHAMSRI, BOONRUANG; KOYAMA, A. HAJIME
Fonte: D.A. Spandidos Publicador: D.A. Spandidos
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.75%
In the present study, dehydroascorbic acid inhibited the multiplication of viruses of three different families: herpes simplex virus type 1 (HSV-1), influenza virus type A and poliovirus type 1. Although dehydroascorbic acid showed some cytotoxicity at higher concentrations, the observed antiviral activity was not the secondary result of the cytotoxic effect of the reagent, as the inhibition of virus multiplication was observed at reagent concentrations significantly lower than those resulting in cytotoxicity. Characterization of the mode of the antiviral action of dehydroascorbic acid against HSV-1 revealed that the addition of reagent at any time post infection inhibited the formation of progeny infectious virus in the infected cells, and a one-step growth curve showed that the addition of reagent allowed formation for an additional 2 h, but then almost completely suppressed it. These results indicate that the reagent inhibits HSV-1 multiplication after the completion of viral DNA replication, probably at the step of the envelopment of viral nucleocapsids at the Golgi apparatus of infected cells.

Dehydroascorbic Acid Attenuates Ischemic Brain Edema and Neurotoxicity in Cerebral Ischemia: An in vivo Study

Song, Juhyun; Park, Joohyun; Kim, Jae Hwan; Choi, Ja Yong; Kim, Jae Young; Lee, Kyoung Min; Lee, Jong Eun
Fonte: The Korean Society for Brain and Neural Science Publicador: The Korean Society for Brain and Neural Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.47%
Ischemic stroke results in the diverse phathophysiologies including blood brain barrier (BBB) disruption, brain edema, neuronal cell death, and synaptic loss in brain. Vitamin C has known as the potent anti-oxidant having multiple functions in various organs, as well as in brain. Dehydroascorbic acid (DHA) as the oxidized form of ascorbic acid (AA) acts as a cellular protector against oxidative stress and easily enters into the brain compared to AA. To determine the role of DHA on edema formation, neuronal cell death, and synaptic dysfunction following cerebral ischemia, we investigated the infarct size of ischemic brain tissue and measured the expression of aquaporin 1 (AQP-1) as the water channel protein. We also examined the expression of claudin 5 for confirming the BBB breakdown, and the expression of bcl 2 associated X protein (Bax), caspase-3, inducible nitric oxide synthase (iNOS) for checking the effect of DHA on the neurotoxicity. Finally, we examined postsynaptic density protein-95 (PSD-95) expression to confirm the effect of DHA on synaptic dysfunction following ischemic stroke. Based on our findings, we propose that DHA might alleviate the pathogenesis of ischemic brain injury by attenuating edema, neuronal loss, and by improving synaptic connection.

Optimization of methodology to analyze ascorbic and dehydroascorbic acid in vegetables

Campos,Flávia Milagres; Ribeiro,Sônia Machado Rocha; Della Lucia,Ceres M.; Pinheiro-Sant'Ana,Helena Maria; Stringheta,Paulo César
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
46.47%
In this study, different solutions to extract vitamin C were tested. High-performance liquid chromatography was chosen and the conditions were based on isocratic elution in reverse phase column. Dehydroascorbic acid was determined indirectly after its reduction using dithiothreitol. The use of metaphosphoric acid to stabilize the vitamin C was shown to be required and it was necessary to neutralize the pH of the extract to apply dithiothreitol. The average recovery was 90% in collard and tomato samples. The presence of oil did not interfere in extraction and the methodology can be used to analyze stir fried vegetables.

Comparative study of six pear cultivars in terms of their phenolic and vitamin C contents and antioxidant capacity

Galvis-Sánchez, Andrea C.; Gil-Izquierdo, Ángel; Gil Muñoz, M.ª Isabel
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artículo Formato: 259768 bytes; application/pdf
ENG
Relevância na Pesquisa
46.72%
9 pages, 8 tables, 1 figure.; The main phenolic compounds in six pear cultivars were identified and quantified using high-performance liquid chromatography/diode array detection (HPLC/DAD) and HPLC/electrospray ionisation mass spectrometry (HPLC/ESIMS). Major quantitative differences were found in the phenolic profiles. The peel contained higher concentrations of chlorogenic acid, flavonols and arbutin than the flesh, where only chlorogenic acid was detected. Total phenolics ranged from 1235 to 2005 mg kg-1 in the peel and from 28 to 81 mg k g-1 in the flesh. Ascorbic acid and dehydroascorbic acid were detected in the peel, whereas only dehydroascorbic acid was present in the flesh. The ranges of vitamin C content were from 116 to 228 mg kg-1 in the peel and from 28 to 53 mg kg-1 in the flesh. The antioxidant capacity was correlated with the content of chlorogenic acid (r = 0.46), while ascorbic acid made only a small contribution to the total antioxidant capacity of the fruit.; ACGS acknowledges the Fundaçäao para a Ciência e Tecnologia (FCT), Portugal for a grant (PRAXIS XXI BD/18392/98). AGI is grateful to the Spanish MEC for a predoctoral grant.; Peer reviewed

Effect of Processing Techniques at Industrial Scale on Orange Juice Antioxidant and Beneficial Health Compounds

Gil-Izquierdo, Ángel; Gil Muñoz, M.ª Isabel; Ferreres, Federico
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 259768 bytes; application/pdf
ENG
Relevância na Pesquisa
46.53%
8 pages, 4 figures, 2 tables.; Phenolic compounds, vitamin C (l-ascorbic acid and l-dehydroascorbic acid), and antioxidant capacity were evaluated in orange juices manufactured by different techniques. Five processes at industrial scale (squeezing, mild pasteurization, standard pasteurization, concentration, and freezing) used in commercial orange juice manufacturing were studied. In addition, domestic squeezing (a hand processing technique) was compared with commercial squeezing (an industrial FMC single-strength extraction) to evaluate their influences on health components of orange juice. Whole orange juice was divided into soluble and cloud fractions after centrifugation. Total and individual phenolics were analyzed in both fractions by HPLC. Commercial squeezing extracted 22% more phenolics than hand squeezing. The freezing process caused a dramatic decrease in phenolics, whereas the concentration process caused a mild precipitation of these compounds to the juice cloud. In pulp, pasteurization led to degradation of several phenolic compounds, that is, caffeic acid derivatives, vicenin 2 (apigenin 6,8-di-C-glucoside), and narirutin (5,7,4‘-trihydroxyflavanone-7-rutinoside) with losses of 34.5, 30.7, and 28%, respectively. Regarding vitamin C...

Characterization and Quantitation of Antioxidant Constituents of Sweet Pepper (Capsicum annuum L.)

Marín Fernández, Alicia; Ferreres, Federico; Tomás Barberán, Francisco; Gil Muñoz, M.ª Isabel
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 259768 bytes; application/pdf
ENG
Relevância na Pesquisa
46.52%
9 pages, 5 tables, 3 figures.; Sweet peppers (Capsicum annuum L.) cv. Vergasa have been studied at four maturity stages (immature green, green, immature red, and red). The individual phenolics (hydroxycinnamic acids and flavonoids), vitamin C (ascorbic acid and dehydroascorbic acid), and individual carotenoids were characterized and quantified. Five hydroxycinnamic derivatives and 23 flavonoids were characterized and quantified from the pericarp of sweet pepper by high-performance liquid chromatography−diode array detection−electrospray ionization−mass spectrometry. Identification was carried out by their UV spectra, chromatographic comparisons with authentic markers, identification of hydrolysis products, and tandem mass spectrometry analysis. Hydroxycinnamic derivatives, O-glycosides of quercetin, luteolin, and chrysoeriol, and a large number of C-glycosyl flavones have been characterized. Some of these compounds were found for the first time in nature. Clear differences in the individual and total phenolic content were detected between the different maturity stages. Immature green pepper had a very high phenolic content while green, immature red, and red ripe peppers showed a 4−5-fold reduction. Ascorbic acid was the main form of vitamin C...

Efflux of hepatic ascorbate: a potential contributor to the maintenance of plasma vitamin C

Upston, Joanne; Karjalainen, Ari; Bygrave, Frank L; Stocker, Roland
Fonte: Portland Press Publicador: Portland Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.5%
Ascorbate (AH, the reduced form of vitamin C) is an important radical scavenger and antioxidant in human plasma; the resulting ascorbyl radical can disproportionate to AH and dehydroascorbic acid (DHA). Here we address potential maintenance mechanism(s) for extracellular AH by examining the ability of cells to convert extracellularly presented DHA to AH. DHA was rapidly transported into human liver (HepG2), endothelial and whole blood cells in vitro by plasma membrane glucose transporters and reduced intracellularly. Liver cells displayed the highest capacity to release the intracellularly accumulated AH. The proteins responsible for DHA uptake and AH release could be distinguished by inhibitor studies. Thus, unlike DHA uptake, AH efflux was largely insensitive to cytochalasin B and thiol-reactive agents but was inhibited by phloretin, 4,4'-di-iso-thiocyanostilbene-2,2'-disulphonate and isoascorbate. Efflux of AH from cells was temperature-sensitive and saturable with a low affinity (millimolar, intracellular) for AH. In addition to isolated liver cells, perfusion of intact rat and guinea-pig liver with DHA resulted in AH in the circulating perfusate. Our results show that hepatocytes take up and reduce DHA and subsequently release part of the AH formed...

An improved and fast UHPLC-PDA methodology for determination of L-ascorbic and dehydroascorbic acids in fruits and vegetables: evaluation of degradation rate during storage

Spínola, Vítor; Mendes, Berta; Câmara, José S.; Castilho, Paula C.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em /01/2012 ENG
Relevância na Pesquisa
56.67%
This study provides a versatile validated method to determine the total vitamin C content, as the sum of the contents of L-ascorbic acid (L-AA) and dehydroascorbic acid (DHAA), in several fruits and vegetables and its degradability with storage time. Seven horticultural crops from two different origins were analyzed using an ultrahigh-performance liquid chromatographic–photodiode array (UHPLC-PDA) system, equipped with a new trifunctional high strength silica (100% silica particle) analytical column (100 mm×2.1 mm, 1.7 μm particle size) using 0.1% (v/v) formic acid as mobile phase, in isocratic mode. This new stationary phase, specially designed for polar compounds, overcomes the problems normally encountered in HPLC and is suitable for the analysis of large batches of samples without L-AA degradation. In addition, it proves to be an excellent alternative to conventional C18 columns for the determination of L-AA in fruits and vegetables. The method was fully validated in terms of linearity, detection (LOD) and quantification (LOQ) limits, accuracy, and inter/intraday precision. Validation experiments revealed very good recovery rate of 96.6±4.4% for L-AA and 103.1±4.8 % for total vitamin C, good linearity with r2-values >0.999 within the established concentration range...

ASCORBIC AND DEHYDROASCORBIC ACID CONTENT OF FROZEN ACEROLA PULP (MALPIGHIA GLABRA L.) COMMERCIALIZED IN RECIFE – PE (BRAZIL); TEOR DE ÁCIDO ASCÓRBICO E DEHIDROASCÓRBICO EM POLPAS DE ACEROLA (Malpighia glabra L.) CONGELADAS E COMERCIALIZADAS NA CIDADE DO RECIFE - PE

LOPES, VERÔNICA CAVALCANTI; Universidade Federal Rural de Pernambuco; MARTINS, MARCOS HENRIQUE BRAINER; Universidade Federal Rural de Pernambuco; CARVALHO, IRINEIDE TEIXEIRA DE; Universidade Federal Rural de Pernambuco
Fonte: UFPR Publicador: UFPR
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Formato: application/pdf
Publicado em 28/04/2009 POR
Relevância na Pesquisa
66.69%
Seventeen samples of frozen acerola pulp (Malphighia glabra L.), processed by different producers and traded in Recife, State of Pernambuco, Brazil, were investigated for the ascorbic acid and dehydroascorbic acid content, from May to June, 1995. The method used was the “Tillmans” with endofenol. The ascorbic acid concentration varied from about 602,41 mg/100 mL to 1575,49 mg/100 mL of frozen pulp.; Analisou-se dezessete amostras de polpas congeladas de acerola (Malpighia glabra L.), processadas por distintos produtores e comercializadas na cidade do Recife, no período de maio a junho de 1995. Verificou-se o teor em ácido ascórbico e dehidroascórbico (método volumétrico de “Tillmans” com indofenol), as condições de armazenamento e embalagem além da coloração das polpas. Os resultados obtidos ficaram abaixo do valor médio de outros estudos, variando de 1575,49 mg/100 mL a 602,41 mg/100 mL de polpa congelada. As condições de embalagem e armazenamento apresentaram-se insatisfatórias, podendo comprometer a vida útil do produto a ser consumido. Recomenda-se que sejam realizados outros trabalhos visando diagnosticar os fatores que podem contribuir na degradação de ácido ascórbico.