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Krishnaja A P - - 2003
Vitamin C (l-ascorbic acid), an effective free radical scavenger present as ascorbate in most biological systems, is one of the most extensively studied antioxidant vitamins. Vitamin C acts as either a free radical scavenger or a pro-oxidant producing hydrogen peroxide and free radicals. The modulatory effect of L-ascorbic acid (AA) ...
Wróbel Anna - - 2003
Bovine erythrocytes treated with peroxynitrite (ONOO(-)), a cytotoxic species formed in vivo via the reaction of nitric oxide (NO(.)) and the superoxide anion (O2(-.)), show an increased rate of hemolysis on sudden osmotic stress. The increase in the rate was peroxynitrite concentration dependent. In the presence of some antioxidants (uric ...
Yokoyama Sadaji - - 2003
The use of a modified ninhydrin reagent using ascorbic acid instead of potassium cyanide was investigated for the photometric determination of amino acids. It has been found possible to obtain an almost stoichiometric reaction for glutamic acid with a quantitative yield of "Ruhemann's purple", the end-product of the reaction, using ...
Morava Eva - - 2003
There is no definitive treatment protocol for alkaptonuria. A patient with alkaptonuria was treated with ascorbic acid (0.5 g/day) from the age of 4 years. He developed episodes of severe recurrent joint pain at 9.5 years of age after which a protein-restricted diet (1.3 g/kg/day) was started. Protein restriction in ...
Negi Pradeep Singh - - 2003
Leafy vegetables are highly perishable and their shelf life depends on duration and conditions of storage. A low cost storage structure was used to extend the shelf life of amaranth and fenugreek and their quality was evaluated on the basis of retention of beta-carotene, ascorbic acid and chlorophyll during storage. ...
Onofri Silvano - - 2003
The alkaloid lycorine, which is considered to inhibit the last step in ascorbic acid biosynthesis, is produced by Narcissus pseudonarcissus. The growth of two strains (C1 and C3) of Cryptococcus laurentii isolated from root tips of N. pseudonarcissus is inhibited by lycorine, as is the in vivo production of ascorbic ...
Forster Markus Paul - - 2002
The contents of moisture, protein, ash, ascorbic acid, glucose, fructose, total sugars, and total and insoluble fiber were determined in cultivars of bananas (Gran Enana and Pequeña Enana) harvested in Tenerife and in bananas (Gran Enana) from Ecuador. The chemical compositions in the bananas from Tenerife and from Ecuador were ...
Lenghor Narong - - 2002
Two sequential injection titration systems with spectrophotometric detection have been developed. The first system for determination of ascorbic acid was based on redox reaction between ascorbic acid and permanganate in an acidic medium and lead to a decrease in color intensity of permanganate, monitored at 525 nm. A linear dependence ...
Koliakos George G - - 2002
PURPOSE: To investigate whether there is a role for ascorbic acid in the development of exfoliation syndrome (XFS). DESIGN: A case-control study was undertaken that included consecutive patients with and without XFS in whom cataract surgery was indicated. Patients with ophthalmic conditions other than XFS and conditions that may influence ...
Kim Won-Suk - - 2002
Ascorbic acid is an important cellular metabolite involved in many biochemical pathways. A method to quantitate ascorbic acid and dehydroascorbic acid in individual neurons and neuronal tissues is described with detection limits of 320 pM (430 zmol). The method uses microvial sampling, derivatization with 4,5-dimethyl-1,2-phenylenediamine, capillary electrophoresis separation, and laser-induced ...
Gütschow Michael - - 2002
The effects of Michael adducts of 6-O-palmitoyl-L-ascorbic acid (compounds 1-4) on the phosphorylation-dependent response of stimulated monocytes and neutrophils was investigated. The pyranosyl derivative 3 increased the production of tumor necrosis factor-alpha in human monocytes stimulated with lipopolysaccharide (LPS). Compound 3 also enhanced the release of tumor necrosis factor-alpha from ...
Cupello A - - 2002
A method is presented for evaluating the concentration of ascorbic acid in 10 microliters samples of cerebrospinal fluid (CSF) with just ultraviolet (UV) scanning in the 220-300 nm range. The method assumes that the two main UV absorbing CSF components are proteins (with a peak at 280 nm) and ascorbic ...
Yamauchi Yasuo - - 2002
Glycation is a process whereby sugar molecules form a covalent adduct with protein amino groups. In this study, we used ascorbic acid (AsA) as a glycating agent and purified cucumber (Cucumis sativus L.) ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) as a model protein in chloroplast tissues, and examined effects of glycation on the ...
Giménez R - - 2002
The ascorbic acid content was determined in 25 different diet supplements commercially available to the consumer in two pharmaceutical forms (pills and ampoules). These products are widely consumed by several population groups (elderly people, sportsmen, adolescents, children, etc.). High-performance liquid chromatography was used as the analytical technique. The proposed method ...
Takebayashi Jun - - 2002
Stoichiometric evaluation of the radical scavenging activity of O-substituted derivatives at the C-2 position of ascorbic acid (AA) was conducted. Their reaction with a stable radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), under an acidic condition was assessed by the colorimetric method. 2-O-alpha-D-Glucopyranosyl-L-ascorbic acid (AA-2G) and a series of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) had long-term ...
Freire Renato S - - 2002
Modification of a gold electrode has been achieved by immobilizing a bis(2,2'-bipyridyl)copper(II) complex in a self-assembled monolayer (SAM) of 3-mercaptopropionic acid. The electrostatic interaction of the negatively charged SAM with a di-positive copper complex allowed the attachment. The modified electrode exhibited excellent redox behavior. The dependence of the modified electrode ...
Rustoiu-Csavdari Alexandra - - 2002
The analytical potential of the redox reactions between N, N-dimethyl- or N, N, N', N'-tetramethyl- p-phenylenediamine (DMPPD or TMPPD, respectively) and peroxodisulfate in acidic media for kinetic spectrophotometric determination of trace amounts of ascorbic acid (AA) has been investigated. The goal was to explore reaction conditions ensuring an excess or ...
Zhang Jingdong - - 2002
The electrooxidation of dopamine (DA) and ascorbic acid (AA) was studied using gold electrodes modified by a cationic self-assembled monolayer of [Os(bpy)2(bpy-(CH2),3SH)]2+ by cyclic voltammetry. At an [Os(bpy)2(bpy-(CH2)13SH)]2+/Au electrode, the oxidation peak of DA shifted to a much more positive potential as compared with that of a bare gold electrode, ...
Mohamed H E - - 2002
There is suggestive evidence that a low status of ascorbic acid in ruminants is related with decreased disease resistance. In a first attempt to identify conditions in camels that could affect their health, an inventory was made of ascorbic acid (vitamin C) concentrations in plasma and tissues as related to ...
Rockwell Sara - - 2002
PURPOSE: To investigate the effects of gadolinium texaphyrin (GdTx) on the growth and radiation response of cells in vitro, in a limited set of experiments designed to examine some areas of controversy concerning the effects of this compound. METHODS AND MATERIALS: Exponentially growing cultures of EMT6 mouse mammary tumor cells, ...
Ensafi Ali A - - 2002
A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at ...
Franceschi Vincent R - - 2002
L-Ascorbic acid (AsA) was found to be loaded into phloem of source leaves and transported to sink tissues. When L-[(14)C]AsA was applied to leaves of intact plants of three different species, autoradiographs and HPLC analysis demonstrated that AsA was accumulated into phloem and transported to root tips, shoots, and floral ...
Lane Michelle - - 2002
BACKGROUND: Embryo development following cryopreservation is reduced compared with fresh embryos. One of the traumas that cryopreservation imparts on embryos is an increase in oxidative stress. Therefore, this study investigated the effects of the addition of the antioxidant ascorbate to the cryopreservation solutions on subsequent embryo development. METHODS: Mouse embryos ...
Morais H - - 2002
The effect of ascorbic acid, light, and storage on the stability of the pigments beta-carotene and capsanthin in red pepper (Capsicum annuum) powder has been elucidated by determining the amount of pigment in samples treated by various concentrations of ascorbic acid. Determination of pigment concentration has been performed after different ...
Gramlich Gabriela - - 2002
The reactivity of the water-soluble antioxidant vitamin C (l-ascorbic acid) depends on pH. It is generally recognized that the ascorbate monoanion, which predominates at neutral physiological pH, acts as a stronger antioxidant than the protonated form, ascorbic acid. Fluorazophore-L, a long-lived fluorescent probe, was employed as a mimic for lipid ...
Carbonaro Marina - - 2002
Despite the increasing interest in organic products, knowledge about how different levels of fertilization affect nutritionally relevant components is still limited. The concentration of polyphenols and the activity of polyphenoloxidase (PPO), together with the content in ascorbic acid, citric acid, and alpha- and gamma-tocopherol, were assayed in conventional and organic ...
Gatto Maria Teresa - - 2002
A new assay for the screening of hypochlorite/hypochlorous acid (XOCl) scavengers, based on the reversed-phase high performance liquid chromatographic analysis of human serum albumin (HSA, 0.2% in 100 mM sodium phosphate, pH 7), before and after oxidation by XOCl (1.6 mM), was developed. XOCl induced a significant decrease of the ...
Ching Simon Y L - - 2002
INTRODUCTION: The stability of ascorbic acid in serum and plasma prior to analysis was studied. METHODS: Blood samples were collected from ten healthy subjects into Vacutainer tubes containing either dipotassium EDTA, lithium-heparin or no additive. Ascorbic acid was analysed following immediate separation and preservation of samples, following delayed separation for ...
Shang Jing - - 2002
Nuclear factor-kappaB (NFkappaB) is a pleiotropic transcriptional activator, which is a sensitive transcriptional factor for free radicals and activates multiple target genes. UVA is very efficient in inducing free radicals in human skin cells. L-ascorbic acid is regarded as a scavenger of UVA-induced free radicals in human keratinocytes. In epidermis, ...
Das Ujjal Baran - - 2002
AIM: To study the detrimental effects of cyclophosphamide on the testicular androgenic and gametogenic activities through endocrine inhibition and/or induction of oxidative stress in male albino rats and to evaluate the protective effect of ascorbic acid. METHODS: The testicular D5, 3b-hydroxysteroid dehydrogenase (HSD), 17b-HSD, peroxidase and catalase activities along with ...
Zou Cheng-Gang - - 2002
In the current work, we investigated the effect of ascorbic acid on GSH-mediated haemin degradation. GSH-mediated haemin degradation in the presence of ascorbic acid in phosphate-buffered saline and in erythrocyte ghosts was determined by recording absorbance at 365 and 399nm, respectively. Generation of intracellular H(2)O(2) was measured indirectly in terms ...
Kikas Timo - - 2002
Dynamic characteristics of the amperometric sensing system for tracking of turbulent chemical plumes have been studied. The correlation analysis requires that such sensors respond rapidly and have long-term stability and minimal or low-flow sensitivity. Moreover, for practical purposes, such sensors must respond to an electrochemical marker that would be found ...
Jin Wenrui - - 2002
A method has been developed for the determination of ascorbic acid (AA) in individual human neutrophils by capillary zone electrophoresis with electrochemical detection at a carbon fiber microdisk bundle electrode. The natively easily oxidized substances such as glutathione, dopa, dopamine, serotonin, epinephrine do not interfere with the determination of ascorbic ...
Lykkesfeldt Jens - - 2002
Ascorbic acid and dehydroascorbic acid are commonly used biomarkers of oxidative stress in a variety of experimental models. However, the accurate measurement of these labile compounds remains a challenge both in terms of sample collection and analysis. Determination of dehydroascorbic acid most commonly involves indirect measurement. The concentration is calculated ...
Daskalopoulos Rina - - 2002
Primary rat astrocyte cultures absorbed dehydroascorbic acid from the medium and reduced it to intracellular ascorbate. Uptake of dehydroascorbic acid (5-200 microM) was inhibited only partially by glucose (10 mM). The remaining glucose-insensitive component of dehydroascorbic acid uptake was inhibited reversibly by sulfinpyrazone (IC(50) = 80 microM). Dehydroascorbic acid uptake ...
Huang Mei - - 2002
Previous studies have shown that acute systemic administration of ethanol induced ascorbic acid release in the striatum. However, the pharmacological implications of ethanol-induced striatal ascorbic acid release are unclear. In the present study, ethanol-induced extracellular changes of ascorbic acid and hydroxyl radical levels were detected in rat striatum by using ...
Obretenov Cvetan - - 2002
High-molecular-weight (HMW) water-soluble melanoidins were prepared from model systems of L-(+)-ascorbic acid-glycine, L-(+)-ascorbic acid-lysine, L-(+)-ascorbic acid-glutamic acid, and glucose-glycine using a very recently approved standard protocol. The amount of HMW water-soluble melanoidins prepared from L-(+)-ascorbic acid was over 5-15 times higher than the amount obtained from glucose. The study of ...
Watanabe Yoshiyuki - - 2002
6-O-Palmitoyl L-ascorbate was added to linoleic acid at various molar ratios of the ascorbate to the acid, the mixtures were emulsified with a maltodextrin or gum arabic solution, and the emulsions were spray-dried to produce microcapsules. At higher molar ratios, the oil droplets in the emulsions were smaller, and the ...
Nakai Akihito - - 2002
Recirculation after transient intrauterine ischemia has previously been found to be accompanied by secondary mitochondrial dysfunction in the immature rat brain. This study was performed to assess the efficacy of combined treatment with ascorbic acid and alpha-tocopherol in improving secondary brain damage. On the 17th day of gestation, transient intrauterine ...
Desai Himadri Sekhar - - 2002
Toxicological effects of some biochemical parameters of freshwater fish Channa punctatus (Bloch), under the stress of Nickel (NiSO4. 6H2O), at various concentrations of 10, 20, 30 and 40 ppm for 30 days were observed. Gradual decrease in the levels of liver protein and liver ascorbic acid due to proteolysis and ...
Li Xia - - 2002
Mitochondria can regenerate ascorbic acid from its oxidized forms, which may help to maintain the vitamin both in mitochondria and in the cytoplasm. In this work, we sought to determine the site and mechanism of mitochondrial ascorbate recycling from dehydroascorbic acid. Rat skeletal muscle mitochondria incubated for 3 h at ...
Wo┼║niak Alina - - 2002
The aim of the paper was to study the effect of ascorbic acid (vitamin C) and ethanol on the level of thiobarbituric acid reactive substances (TBARS) in the brain, liver, lungs and blood serum of inbred albino BALB/c mice. Sixty male mice divided into 4 groups were used for the ...
Gerber Claudia E - - 2002
Granulocytes contain large quantities of ascorbic acid (AA). The uptake mechanism is mainly restricted to the accumulation of the oxidized form, dehydroascorbate (DHA). We investigated the uptake of ascorbic acid and dehydroascorbate of normal, myeloperoxidase (MPO)-deficient, and NADPH-oxidase-deficient granulocytes. The accumulation of ascorbic acid was increased in all types of ...
Trommer Hagen - - 2002
PURPOSE: The effects of ascorbic acid on Stratum corneum lipid models following ultraviolet irradiation were studied adding iron ions as transition metal catalysts. METHODS: Lipid peroxidation was quantified by the thiobarbituric acid assay. The qualitative changes were studied on a molecular level by mass spectrometry. To elucidate the nature of ...
Paim Ana Paula S - - 2002
A flow procedure for the determination of ascorbic acid in pharmaceutical formulations exploiting potentiometric titration is described. The method is based on the reduction of IO3- by ascorbic acid and the detection was carried out employing a flow-through ion selective electrode for iodide. The flow network controlled by a microcomputer ...
Ortega-Barrales P - - 2002
A continuous and simple UV-photometric flow-through optosensor has been developed for the simultaneous determination of a binary mixture of two species with different electric charges present at very different concentrations - ascorbic acid (or acetylsalicylic acid) and thiamine. The sensing device is based on the selective sorption and determination of ...
Giovine Marco - - 2002
Quartz incubated in an aqueous solution of ascorbic acid is partially dissolved and the potential to generate hydroxyl radicals from hydrogen peroxide is enhanced. In order to investigate whether the surface activation triggered by the treatment with ascorbic acid would also involve an enhancement in cell toxicity, a murine macrophage ...
Ouattara Blaise - - 2002
This study was conducted to evaluate the combined effect of gamma irradiation and the incorporation of natural antimicrobial compounds in cross-linked films on the microbiological and biochemical characteristics of ground beef. Medium-fat (23% fat) ground beef patties were divided into three separate treatment groups: (i) control samples without additives, (ii) ...
Bae Hee-Kyung - - 2002
Ascorbic acid (1), a natural antioxidant, was modified by employing transglycosylation activity of Bacillus stearothermophilus maltogenic amylase with maltotriose and acarbose as donor molecules to enhance its oxidative stability. The transglycosylation reaction with maltotriose as donor created mono- and di-glycosyl transfer products with an alpha-(1,6)-glycosidic linkage. In addition, two acarviosine-glucosyl ...
Miura Yasuyuki - - 2002
Rapid separation and determination of mixtures of L-ascorbic acid, nitrite, sulfite, oxalate, iodide and thiosulfate by conventional ion chromatography is often difficult due to incomplete separation of L-ascorbic acid and nitrite from the water peak when using eluents giving short elution times for iodide and thiosulfate. Separation of the six ...
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