Showing papers on "Ascorbic acid published in 2008"

Combined Impact of Health Behaviours and Mortality in Men and Women: The EPIC-Norfolk Prospective Population Study

Abstract: Background There is overwhelming evidence that behavioural factors influence health, but their combined impact on the general population is less well documented. We aimed to quantify the potential combined impact of four health behaviours on mortality in men and women living in the general community.

Catalyst-Free Efficient Growth, Orientation and Biosensing Properties of Multilayer Graphene Nanoflake Films with Sharp Edge Planes**

Abstract: We report a novel microwave plasma enhanced chemical vapor deposition strategy for the efficient synthesis of multilayer graphene nanoflake films (MGNFs) on Si substrates The constituent graphene nanoflakes have a highly graphitized knife-edge structure with a 2-3 nm thick sharp edge and show a preferred vertical orientation with respect to the Si substrate as established by near-edge X-ray absorption fine structure spectroscopy The growth rate is approximately 16 mu m min(-1), which is 10 times faster than the previously reported best value The MGNFs are shown to demonstrate fast electron-transfer (ET) kinetics for the Fe(CN)(6)(3-/4-) redox system and excellent electrocatalytic activity for simultaneously determining dopamine (DA), ascorbic acid (AA) and uric acid (UA) Their biosensing DA performance in the presence of common interfering agents AA and UA is superior to other bare solid-state electrodes and is comparable only to that of edge plane pyrolytic graphite Our work here, establishes that the abundance of graphitic edge planes/defects are essentially responsible for the fast ET kinetics, active electrocatalytic and biosensing properties This novel edge-plane-based electrochemical platform with the high surface area and electrocatalytic activity offers great promise for creating a revolutionary new class of nanostructured electrodes for biosensing, biofuel cells and energy-conversion applications

Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice.

Abstract: Ascorbic acid is an essential nutrient commonly regarded as an antioxidant. In this study, we showed that ascorbate at pharmacologic concentrations was a prooxidant, generating hydrogen-peroxide-dependent cytotoxicity toward a variety of cancer cells in vitro without adversely affecting normal cells. To test this action in vivo , normal oral tight control was bypassed by parenteral ascorbate administration. Real-time microdialysis sampling in mice bearing glioblastoma xenografts showed that a single pharmacologic dose of ascorbate produced sustained ascorbate radical and hydrogen peroxide formation selectively within interstitial fluids of tumors but not in blood. Moreover, a regimen of daily pharmacologic ascorbate treatment significantly decreased growth rates of ovarian ( P P P

Acrolein: sources, metabolism, and biomolecular interactions relevant to human health and disease.

Abstract: Acrolein (2-propenal) is ubiquitously present in (cooked) foods and in the environment. It is formed from carbohydrates, vegetable oils and animal fats, amino acids during heating of foods, and by combustion of petroleum fuels and biodiesel. Chemical reactions responsible for release of acrolein include heat-induced dehydration of glycerol, retro-aldol cleavage of dehydrated carbohydrates, lipid peroxidation of polyunsaturated fatty acids, and Strecker degradation of methionine and threonine. Smoking of tobacco products equals or exceeds the total human exposure to acrolein from all other sources. The main endogenous sources of acrolein are myeloperoxidase-mediated degradation of threonine and amine oxidase-mediated degradation of spermine and spermidine, which may constitute a significant source of acrolein in situations of oxidative stress and inflammation. Acrolein is metabolized by conjugation with glutathione and excreted in the urine as mercapturic acid metabolites. Acrolein forms Michael adducts with ascorbic acid in vitro, but the biological relevance of this reaction is not clear. The biological effects of acrolein are a consequence of its reactivity towards biological nucleophiles such as guanine in DNA and cysteine, lysine, histidine, and arginine residues in critical regions of nuclear factors, proteases, and other proteins. Acrolein adduction disrupts the function of these biomacromolecules which may result in mutations, altered gene transcription, and modulation of apoptosis.

In vitro antioxidant properties of rutin

Abstract: Much work has been carried out in recent years on the beneficial effect of phenolic compounds which act as natural antioxidants and help to neutralize free radicals. We analysed the antioxidant activity of the rutin (quercetin-3-rhamnosyl glucoside) using different assays including: total antioxidant activity and reducing power, hydroxyl radical scavenging assay, superoxide radical scavenging assay, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay and lipid peroxidation assay which uses egg yolk as the lipid-rich source. Total antioxidant capacity was determined by the assay based on the decrease in absorbance of β-carotene by the sample. Rutin exhibited strong DPPH radical scavenging activity. At the concentration of 0.05 mg/ml, ascorbic acid (Vc), butylated hydroxytoluene (BHT) and rutin showed 92.8%, 58.8%, and 90.4% inhibition, respectively. In addition, rutin had effective inhibition of lipid peroxidation. Those various antioxidant activities were compared to standard antioxidants such as BHT and Vc.

Nonenzymatic Electrochemical Glucose Sensor Based on Nanoporous PtPb Networks

Abstract: Here, we report on a novel nonenzymatic amperometric glucose sensor based on three-dimensional PtPb networks directly grown on Ti substrates using a reproducible one-step hydrothermal method. The surface morphology and bimetallic composition of the synthesized nanoporous PtPb materials were characterized using scanning electron microscopy and energy-dispersive X-ray spectrometry, respectively. Voltammetry and amperometric methods were used to evaluate the electrocatalytic activities of the synthesized electrodes toward nonenzymatic glucose oxidation in neutral media in the absence and in the presence of chloride ions. The synthesized nanoporous PtPb electrodes have strong and sensitive current responses to glucose. Their amperometric sensitivities increase in the order of Pt-Pb (0%) < Pt-Pb (30%) < Pt-Pb (70%) < Pt-Pb (50%). These nanoporous PtPb electrodes are also highly resistant toward poisoning by chloride ions and capable of sensing glucose amperometrically at a very low potential, -80 mV (Ag/AgCl), where the interference from the oxidation of common interfering species such as ascorbic acid, acetamidophenol, and uric acid is effectively avoided.

Salt tolerance of barley induced by the root endophyte Piriformospora indica is associated with a strong increase in antioxidants

Abstract: The root endophytic basidiomycete Piriformospora indica has been shown to increase resistance against biotic stress and tolerance to abiotic stress in many plants. Biochemical mechanisms underlying P. indica-mediated salt tolerance were studied in barley (Hordeum vulgare) with special focus on antioxidants. Physiological markers for salt stress, such as metabolic activity, fatty acid composition, lipid peroxidation, ascorbate concentration and activities of catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase and glutathione reductase enzymes were assessed. Root colonization by P. indica increased plant growth and attenuated the NaCl-induced lipid peroxidation, metabolic heat efflux and fatty acid desaturation in leaves of the salt-sensitive barley cultivar Ingrid. The endophyte significantly elevated the amount of ascorbic acid and increased the activities of antioxidant enzymes in barley roots under salt stress conditions. Likewise, a sustained up-regulation of the antioxidative system was demonstrated in NaCl-treated roots of the salt-tolerant barley cultivar California Mariout, irrespective of plant colonization by P. indica. These findings suggest that antioxidants might play a role in both inherited and endophyte-mediated plant tolerance to salinity.

Effects of Different Cooking Methods on Nutritional and Physicochemical Characteristics of Selected Vegetables

Abstract: The objective of the present study was to evaluate the effect of three common cooking practices (i.e., boiling, steaming, and frying) on phytochemical contents (i.e., polyphenols, carotenoids, glucosinolates, and ascorbic acid), total antioxidant capacities (TAC), as measured by three different analytical assays [Trolox equivalent antioxidant capacity (TEAC), total radical-trapping antioxidant parameter (TRAP), ferric reducing antioxidant power (FRAP)] and physicochemical parameters of three vegetables (carrots, courgettes, and broccoli). Water-cooking treatments better preserved the antioxidant compounds, particularly carotenoids, in all vegetables analyzed and ascorbic acid in carrots and courgettes. Steamed vegetables maintained a better texture quality than boiled ones, whereas boiled vegetables showed limited discoloration. Fried vegetables showed the lowest degree of softening, even though antioxidant compounds were less retained. An overall increase of TEAC, FRAP, and TRAP values was observed in all cooked vegetables, probably because of matrix softening and increased extractability of compounds, which could be partially converted into more antioxidant chemical species. Our findings defy the notion that processed vegetables offer lower nutritional quality and also suggest that for each vegetable a cooking method would be preferred to preserve the nutritional and physicochemical qualities.

In vitro antioxidant properties of rutin

Abstract: Much work has been carried out in recent years on the beneficial effect of phenolic compounds which act as natural antioxidants and help to neutralize free radicals. We analysed the antioxidant activity of the rutin (quercetin-3-rhamnosyl glucoside) using different assays including: total antioxidant activity and reducing power, hydroxyl radical scavenging assay, superoxide radical scavenging assay, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay and lipid peroxidation assay which uses egg yolk as the lipid-rich source. Total antioxidant capacity was determined by the assay based on the decrease in absorbance of β-carotene by the sample. Rutin exhibited strong DPPH radical scavenging activity. At the concentration of 0.05 mg/ml, ascorbic acid (Vc), butylated hydroxytoluene (BHT) and rutin showed 92.8%, 58.8%, and 90.4% inhibition, respectively. In addition, rutin had effective inhibition of lipid peroxidation. Those various antioxidant activities were compared to standard antioxidants such as BHT and Vc.

Direct observation of chemical reactions on single gold nanocrystals using surface plasmon spectroscopy.

Abstract: Heterogeneous catalysts have been pivotal to the development of the modern chemical industry and are essential for catalysing many industrial reactions. However, reaction rates are different for every individual catalyst particle and depend upon each particle's morphology and size, crystal structure and composition. Measuring the rates of reaction on single nanocrystals will enable the role of catalyst structure to be quantified. Here, using surface plasmon spectroscopy, we have directly observed the kinetics of atomic deposition onto a single gold nanocrystal and also monitored electron injection and extraction during a redox reaction involving the oxidation of ascorbic acid on a gold nanocrystal surface. These results constitute the first direct measurement of the rates of redox catalysis on single nanocrystals.

Antioxidant activity of three edible seaweeds from two areas in South East Asia

Abstract: Total phenolic content (TPC) and antioxidant activity (AOA) of 50% aqueous methanol extracts of the marine algae, Padina antillarum, Caulerpa racemosa and Kappaphycus alvarezzi were studied. TPC was measured using Folin–Ciocalteu method while 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), ferrous ion chelating (FIC) assay and beta carotene bleaching (BCB) assay were used to study their AOA. P. antillarum was found to have the highest TPC, 2430±208 mg gallic acid equivalents (GAE) per 100 g dried sample and ascorbic acid equivalent antioxidant capacity (AEAC), 1140±85 mg AA/100 g. C. racemosa and K. alvarezzi displayed lower TPC and AEAC. C. racemosa had 144±22 mg GAE/100 g dried sample of TPC and 14.3±2.0 mg AA/100 g of AEAC, while K. alvarezzi had 115±35 mg/100 g dried sample of TPC and 37.8±16.8 mg AA/100 g of AEAC. In addition, P. antillarum displayed the highest reducing power, 15.7±2.6 mg GAE/g and highest chelating ability. C. racemosa and K. alvarezzi exhibited lower reducing power, 0.737±0.423 mg GAE/g and 0.561±0.269 mg GAE/g, and lower chelating ability. However, the AOA of these three seaweeds as assessed by BCB assay were equally high.

Antioxidant Activity of Some Common Plants

Abstract: The methanolic crude extracts of some commonly used medicinal plants were screened for their free radical scavenging properties using ascorbic acid as standard antioxidant. Free radical scavenging activity was evaluated using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical. The overall antioxidant activity of green tea (Camellia sinensis Linn.) was the strongest, followed in descending order by black tea (Camellia sinensis Linn.), Eugenia caryophyllus (Spreng.) Bullock and Harrison, Piper cubeba Linn., Zingiber officinale Roscoe and Piper nigrum Linn. Trigonella foenum graecum Linn. and Elettaria cardamomum (Linn.) Maton showed weak free radical scavenging activity with the DPPH method. All the methanolic extracts exhibited antioxidant activity significantly. The IC50 of the methanolic extracts ranged between 6.7 ± 0.1 and 681.5 ± 8.4 µg/ml and that of ascorbic acid was 8.9 ± 0.1 µg/ml. The study reveals that the consumption of these spices would exert several beneficial effects by virtue of their antioxidant activity.

Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid

Abstract: Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid Hyunjoo Lee †‡ , Susan E. Habas ‡ , Gabor A. Somorjai ‡ , and Peidong Yang ‡ Department of Chemical Engineering, Yonsei University, Seoul, South Korea, Department of Chemistry, University of California, Berkeley, California 94720, USA, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA Email: p_yang@uclink.berkeley.edu RECEIVED DATE ; Single crystalline surface such as (100), (111), (110) has been studied as an idealized platform for electrocatalytic reactions since the atomic arrangement affects a catalytic property. The secondary metal deposition on these surfaces also alters the catalytic property often showing improvement such as poisoning decrease. On the other hand, electrocatalysts used for practical purpose usually have a size on the order of nanometers. Therefore, linking the knowledge from single crystalline studies to nanoparticle catalysts is of enormous importance. Recently, the Pt nanoparticles which surface structure was preferentially oriented was synthesized and used as electrocatalysts 12 . Here, we demonstrate a rational design of a binary metallic nanocatalyst based on the single crystalline study. Clavilier et al. studied the electro-oxidation of formic acid for Pd adsorbed on Pt(100) single crystal surfaces. 5 They observed that the presence of adsorbed palladium on Pt(100) decreases self- poisoning and lowers the oxidation potential considerably. The multi-metallic nanoparticle catalysts, however, were usually prepared by co-precipitation 6 or electrodeposition 7 , and control over surface structure was not achieved. We present the synthesis and application of binary Pt/Pd nanoparticles in which Pd decorates the well-defined surface of Pt nanoparticles. Pt nanocubes fully bound by (100) surfaces acted as seeds for overgrowth of Pd. Overgrowth was observed at multiple points on each seed, predominantly at the corners. Electro-oxidation of formic acid performed on these binary Pt/Pd catalysts showed the same effects of less poisoning and lower oxidation potential expected from the single crystal study. Preparation of metal nanoparticles with shape control has often been achieved by controlling growth rates on different facets through interactions with surface-stabilizing agents. 8 However, since the catalytic activity is hindered by these surface-stabilizing agents, 9 preserving the catalytic activity of the metal surface is crucial. In this study, we used tetradecyltrimethylammonium bromide (TTAB) as a surface-stabilizing agent since it has a weak interaction with metal surfaces 9a . The cubic Pt nanoparticles used as seeds were prepared by reducing K 2 PtCl 4 dissolved in aqueous TTAB solution with NaBH 4 as previously reported. 9a A TEM image of the cubic Pt seed particles is shown in Figure S1(a). Pd was nucleated on the surface of cubic Pt seeds upon reduction of K 2 PdCl 4 by ascorbic acid in the presence of TTAB (See Supporting Information for more details). Figure 1(a) shows a low magnification TEM image of the binary Pt/Pd nanoparticles. Single, double and multiple nucleation of Pd on Pt nanoparticles was observed with nucleation occurring primarily on the corners. High resolution TEM images in Figures 1(b) show the interface of Figure 1. TEM images of (a) binary Pt/Pd nanoparticles, HR-TEM images of (b) Pt/Pd interface with an atomic resolution, (c) high Pd coverage and (d) low Pd coverage of binary Pt/Pd nanoparticles. the two metals more clearly. Pd grew on Pt surface epitaxially. Figure 1(c) and (d) show a high and low coverage of Pd on Pt surface. The formation of multiple nucleation sites of Pd on the Pt seeds rather than conformal overgrowth depends on the rate of reduction which was controlled through pH. The addition of as- made Pt seeds (pH~9) also introduces the strongly basic metaborate ion (BO 2- ) formed during the reaction of NaBH 4 with water. The higher pH increases the rate of Pd reduction, probably due to better stabilization of the oxidized form of the ascorbic acid. The increased rate of reduction may encourage the formation of multiple nucleation sites rather than the conformal overgrowth of a thin Pd shell which was observed when the Pt seeds were acidified to a neutral pH 10 . The addition of base to bring the pH of the seed solution back to ~9 once again allows for the formation of multiple nucleation sites. Fully grown cubic Pd nanoparticles with a cubic Pt seed inside, shown in Figure S1(b), were prepared by decreasing the concentration of Pt seeds along with the pH. This type of epitaxial overgrowth was demonstrated previously. 12 While both the Pt and Pd surfaces are accessible on the binary Pt/Pd nanoparticles, only the Pd surface is available on the core- shell Pt/Pd nanocubes. Pd nanoparticles without Pt seeds were also prepared as shown in Figure S1(c) for comparison.

In vitro antioxidant activities of the fractions of Coccinia grandis L. leaf extract.

Abstract: The present study was aimed at investigating the antioxidant activities of the various fractions of the hydromethanolic extract of the leaves of Coccinia grandis L. Voigt. (Cucurbitaceae). The antioxidant activities of the fractions have been evaluated by using nine in vitro assays and were compared to standard antioxidants such as ascorbic acid, α-tocopherol, curcumin and butylated hydroxyl toluene (BHT). All the fractions showed effective H-donor activity, reducing power, free radical scavenging activity, metal chelating ability and inhibition of β-carotene bleaching. None of the fractions exerted an obvious pro-oxidant activity. The antioxidant property depends upon concentration and increased with increasing amount of the fractions. The free radical scavenging and antioxidant activities may be attributed to the presence of phenolic and flavonoid compounds present in the fractions. The results obtained in the present study indicate that the leaves of C. grandis are a potential source of natural antioxidant.

Reducing, radical scavenging, and chelation properties of in vitro digests of alcalase-treated zein hydrolysate.

Abstract: The objective of the study was to assess the antioxidant potential of alcalase-treated zein hydrolysate (ZH) during a two-stage (1 h of pepsin --> 0.5-2 h of pancreatin, 37 degrees C) in vitro digestion. Sephadex gel filtration and high-performance size exclusion chromatography were used to separate ZH into fractions. The amino acid composition, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+*)) and 1,1-diphenyl-2-picrylhydrazyl (DPPH*) free radical scavenging activity, reducing power, and Cu (2+) chelation ability were tested to determine the antioxidant efficacy of ZH. Results showed that in vitro digests of ZH contained up to 16.5% free amino acids, with short peptides (<500 Da) making up the rest of the mass. The ABTS(+*) scavenging activity of ZH was decreased by 27% (P<0.05) after pepsin treatment but was fully recovered upon subsequent pancreatin digestion, while the DPPH* scavenging activity of ZH was substantially less than ABTS(+*) scavenging activity and showed a 7-fold reduction following pancreatin treatment. The reducing power of ZH increased 2-fold (P<0.05) following pancreatin digestion when compared with nondigested ZH. The ability of ZH to sequester Cu (2+) was reduced by pepsin digestion but was reestablished following pancreatin treatment. The antioxidant activity demonstrated by in vitro digests of ZH (1-8 mg/mL) was comparable to or exceeded (P<0.05) that of 0.1 mg/mL of ascorbic acid or BHA. The results suggested that dietary zein alcalase hydrolysate may have the benefit to promote the health of the human digestive tract.