Kinetics of the reduction of water-soluble colloidal MnO2 by ascorbic acid

AbstractThe kinetics of the degradation of metribuzin by water-soluble colloidal MnO2 in acidic medium (HClO4) were studied spectrophotometrically in the absence and presence of surfactants. The experiments were performed under pseudo-first-order reaction conditions in respect of MnO2. The degradation was observed to be of the first order in respect of MnO2 while of fractional order for both metribuzin and HClO4. The rate constant for the degradation of metribuzin was observed to decrease as the concentration of MnO2 increased. The anionic surfactant, sodium dodecyl sulphate (SDS), was observed to be ineffective whereas the non-ionic surfactant, Triton X-100 (TX-100), accelerated the reaction rate. However, the cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), caused flocculation with oppositely-charged colloidal MnO2; hence further study was not possible. The catalytic effect of TX-100 was discussed in the light of the available mathematical model. The kinetic data were exploited to generate the various activation parameters for the oxidative degradation of metribuzin by colloidal MnO2 in the absence as well as the presence of the non-ionic surfactant, TX-100.

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Kinetics of the reduction of water soluble colloidal MnO2 by mandelic acid in the absence and presence of non-ionic surfactant triton X-100

Colloid Journal ◽

10.1134/s1061933x10020080 ◽

2010 ◽

Vol 72 (2) ◽

pp. 195-204 ◽

Cited By ~ 7

Author(s):

Kabir-ud-Din ◽

S. M. Shakeel Iqubal

Keyword(s):

Mandelic Acid ◽

Water Soluble ◽

Ionic Surfactant ◽

Colloidal Mno2 ◽

Triton X ◽

Kinetics Of

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Nitrogen dioxide depletes uric acid and ascorbic acid but not glutathione from lung lining fluid

Biochemical Journal ◽

10.1042/bj3250095 ◽

1997 ◽

Vol 325 (1) ◽

pp. 95-99 ◽

Cited By ~ 32

Author(s):

Frank J. KELLY ◽

Teresa D. TETLEY

Keyword(s):

Ascorbic Acid ◽

Uric Acid ◽

Nitrogen Dioxide ◽

Ex Vivo ◽

Water Soluble ◽

Model Complexity ◽

Antioxidant Defences ◽

Consumption Rates ◽

Lung Lining Fluid ◽

Kinetics Of

The aim of this study was to determine the kinetics of the reactions between the gaseous free-radical pollutant, nitrogen dioxide (NO2), and the water-soluble antioxidants present in respiratory tract lining fluid (RTLF). Samples of RTLF, recovered from 12 subjects (mean age 54.1±16.3 years; eight male, four female) as bronchoalveolar lavage (BAL) fluid were exposed ex vivo to NO2 [50–1000 parts per billion (ppb)] for 4 h. For comparison, similar exposures were carried out with single and composite solutions with relevant RTLF antioxidant concentrations. Ascorbic acid (AA), uric acid (UA), GSH depletion, and GSSG and malondialdehyde (MDA) formation were determined with time. In the three models, UA and AA were consumed in a time- and NO2-concentration-related fashion. In addition, their rate of depletion correlated positively with their initial concentration (UA, r = 0.92, P < 0.05; AA, r = 0.94, P < 0.05). Little difference was found between the rate of loss of AA (2.2±0.2; 1.9±0.5; 1.4±0.3 nmol·l-1·h-1·ppb-1), and that of UA (2.4±0.2; 2.1±0.6; 1.3±0.2 nmol·l-1·h-1·ppb-1) in the three RTLF models examined (single, composite, BAL fluid respectively). GSH loss from BAL fluid (0.2±0.1) was significantly less than that seen in either single (1.4±0.3) or composite (1.2±0.5 nmol·l-1·h-1·ppb-1) antioxidant solutions. In all cases, GSH consumption was significantly less than AA or UA. As model complexity increased, the rate of individual antioxidant loss decreased, such that in BAL fluid, AA, UA and GSH consumption rates were significantly less (P < 0.05) than in the pure or composite antioxidant mixtures. In BAL fluid, little GSSG production was observed at any NO2 concentration. MDA concentration, determined as a measure of lipid peroxidation, did not change following exposure to 50, 150 or 400 ppb NO2, but increased MDA was seen in BAL fluid from 8/12 subjects following exposure to 1000 ppb NO2 for 1 h or more. In conclusion, NO2, at environmentally relevant concentrations, depletes BAL fluid of the antioxidant defences, UA and AA, but not GSH.

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Sorbitol enhances the physicochemical stability of B12 vitamers

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000578 ◽

2020 ◽

Vol 90 (5-6) ◽

pp. 439-447 ◽

Cited By ~ 1

Author(s):

Andrew Hadinata Lie ◽

Maria V Chandra-Hioe ◽

Jayashree Arcot

Keyword(s):

Ascorbic Acid ◽

Uv Light ◽

Heat Exposure ◽

Water Soluble ◽

Uv Exposure ◽

Physicochemical Stability ◽

Before And After ◽

The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

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Ascorbic Acid does not Improve Endothelium-Dependent Flow-mediated Dilatation of the Brachial Artery in Patients with Raynaud’s Phenomenon Secondary to Systemic Sclerosis

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831.73.1.3 ◽

2003 ◽

Vol 73 (1) ◽

pp. 3-7 ◽

Cited By ~ 22

Author(s):

M. E. Mavrikakis ◽

J. P. Lekakis ◽

M. Papamichael ◽

K. S. Stamatelopoulos ◽

Ch. C. Kostopoulos ◽

...

Keyword(s):

Ascorbic Acid ◽

Smooth Muscle ◽

Systemic Sclerosis ◽

Endothelial Dysfunction ◽

Brachial Artery ◽

Raynaud’S Phenomenon ◽

Raynaud's Phenomenon ◽

Water Soluble ◽

Placebo Administration ◽

Flow Mediated Dilatation

Previous studies have shown that patients with Raynaud’s phenomenon secondary to systemic sclerosis present abnormal endothelial function; the mechanisms responsible for the endothelial dysfunction are unknown but increased vascular oxidative stress could be a possible cause. The hypothesis that a potent water-soluble antioxidant can reverse endothelial dysfunction in these patients was tested in the present study. We examined 11 female patients with Raynaud’s phenomenon secondary to systemic sclerosis and ten healthy control women by ultrasound imaging of the brachial artery to assess flow-mediated (endothelium-dependent) and nitrate-induced (endothelium-independent) vasodilatation. Flow-mediated dilatation and nitrate-induced dilatation were significantly reduced in patients with Raynaud’s phenomenon, indicating abnormal endothelial and smooth muscle cell function. Patients with Raynaud’s phenomenon entered a double-blind, randomized, crossover placebo-controlled trial and received orally 2 g of ascorbic acid or placebo; vascular studies were repeated two hours after ascorbic acid or placebo administration. Flow-mediated dilatation did not improve after ascorbic acid (1.6 ± 2.2% to 2.2 ± 2.5%, ns) or placebo administration (1.2 ± 1,9% to 1.7 ± 1.4%, ns); also nitrate-induced dilatation was similar after ascorbic acid or placebo (16 ± 7.4% vs 17 ± 8%, ns), suggesting no effect of ascorbic acid on endothelial and vascular smooth muscle function. In conclusion, ascorbic acid does not reverse endothelial vasomotor dysfunction in the brachial circulation of patients with Raynaud’s phenomenon secondary to systemic sclerosis. The use of different antioxidants or different dosing of ascorbic acid may be required to show a beneficial effect on endothelial vasodilator function.

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Molecularly Imprinted Sensor for Ascorbic Acid Based on Gold Nanoparticles and Multiwalled Carbon Nanotubes

Current Analytical Chemistry ◽

10.2174/1573411015666191029152332 ◽

2020 ◽

Vol 16 (7) ◽

pp. 905-913

Author(s):

Youyuan Peng ◽

Qingshan Miao

Keyword(s):

Carbon Nanotubes ◽

Gold Nanoparticles ◽

Ascorbic Acid ◽

Multiwalled Carbon Nanotubes ◽

Ph Value ◽

Biological Fluids ◽

Water Soluble ◽

Multiwalled Carbon ◽

Experimental Conditions ◽

Molecularly Imprinted

Background: L-Ascorbic acid (AA) is a kind of water soluble vitamin, which is mainly present in fruits, vegetables and biological fluids. As a low cost antioxidant and effective scavenger of free radicals, AA may help to prevent diseases such as cancer and Parkinson’s disease. Owing to its role in the biological metabolism, AA has also been utilized for the therapy of mental illness, common cold and for improving the immunity. Therefore, it is very necessary and urgent to develop a simple, rapid and selective strategy for the detection of AA in various samples. Methods: The molecularly imprinted poly(o-phenylenediamine) (PoPD) film was prepared for the analysis of L-ascorbic acid (AA) on gold nanoparticles (AuNPs) - multiwalled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE) by electropolymerization of o-phenylenediamine (oPD) and AA. Experimental parameters including pH value of running buffer and scan rates were optimized. Scanning electron microscope (SEM), fourier-transform infrared (FTIR) spectra, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for the characterization of the imprinted polymer film. Results: Under the selected experimental conditions, the DPV peak currents of AA exhibit two distinct linear responses ranging from 0.01 to 2 μmol L-1 and 2 to 100 μmol L-1 towards the concentrations of AA, and the detection limit was 2 nmol L-1 (S/N=3). Conclusion: The proposed electrochemical sensor possesses excellent selectivity for AA, along with good reproducibility and stability. The results obtained from the analysis of AA in real samples demonstrated the applicability of the proposed sensor to practical analysis.

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Synthesis of Fluorescent Carbon Dots and Their Application in Ascorbic Acid Detection

Molecules ◽

10.3390/molecules26051246 ◽

2021 ◽

Vol 26 (5) ◽

pp. 1246

Author(s):

Tengfei Wang ◽

Hui Luo ◽

Xu Jing ◽

Jiali Yang ◽

Meijun Huo ◽

...

Keyword(s):

Ascorbic Acid ◽

Fluorescence Intensity ◽

Carbon Dots ◽

Ph Dependence ◽

Scale Up ◽

Water Soluble ◽

Jujube Fruit ◽

Fluorescent Carbon Dots ◽

Fluorescent Carbon

Water-soluble fluorescent carbon dots (CDs) were synthesized by a hydrothermal method using citric acid as the carbon source and ethylenediamine as the nitrogen source. The repeated and scale-up synthetic experiments were carried out to explore the feasibility of macroscopic preparation of CDs. The CDs/Fe3+ composite was prepared by the interaction of the CDs solution and Fe3+ solution. The optical properties, pH dependence and stability behavior of CDs or the CDs/Fe3+ composite were studied by ultraviolet spectroscopy and fluorescence spectroscopy. Following the principles of fluorescence quenching after the addition of Fe3+ and then the fluorescence recovery after the addition of asorbic acid, the fluorescence intensity of the carbon dots was measured at λex = 360 nm, λem = 460 nm. The content of ascorbic acid was calculated by quantitative analysis of the changing fluorescence intensity. The CDs/Fe3+ composite was applied to the determination of different active molecules, and it was found that the composite had specific recognition of ascorbic acid and showed an excellent linear relationship in 5.0–350.0 μmol·L−1. Moreover, the detection limit was 3.11 μmol·L−1. Satisfactory results were achieved when the method was applied to the ascorbic acid determination in jujube fruit. The fluorescent carbon dots composites prepared in this study may have broad application prospects in a rapid, sensitive and trace determination of ascorbic acid content during food processing.

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