Search results for "ascorbic acid"
showing 10 items of 295 documents
Determination of ascorbic acid in asparagus by differential pulse polarography
1995
A useful method for the determination of ascorbic acid in a vegetable product (asparagus) by differential pulse polarography has been set up and evaluated. Extraction and instrumental conditions were optimized. The analytical parameters are: linearity (0–18.18 μg/ml); detection limit (0.182 μg/ml); instrumental and method precision (2.77% and 4%, respectively); accuracy (96.9–113.4%). These data show that the method is sufficiently sensitive, reliable and accurate. It was also compared with the official fluorometric AOAC method.
Non-chromatographic speciation of inorganic arsenic in mushrooms by hydride generation atomic fluorescence spectrometry
2009
Abstract A non-chromatographic speciation method has been developed for the determination of inorganic arsenic in cultivated and wild mushroom samples from different origins. The ultrasound-assisted extraction of the toxic arsenic species As (III) and As (V) was performed for 10 min with 1 mol l −1 H 3 PO 4 and 0.1% (m/v) Triton X-100. After phase separation the residue was washed with 0.1% (w/v) EDTA and centrifuged. As (III) and As (V) were determined by hydride generation atomic fluorescence spectrometry. Speciation was made using proportional equations corresponding to two different measurement conditions, (i) directly feeding sample extracts diluted with HCl and (ii) after reduction wi…
Determination of As, Sb, Se, Te and Bi in milk by slurry sampling hydride generation atomic fluorescence spectrometry
2003
A simple and fast analytical procedure has been developed for the determination of As, Sb, Se, Te and Bi in milk samples by hydride generation atomic fluorescence spectrometry (HG-AFS). Samples were treated with aqua regia for 10min in an ultrasound water bath and pre-reduced with KBr for total Se and Te determination or with KI and ascorbic acid for total As and Sb, the determination of Bi being possible in all with or without pre-reduction. Slurries of samples, in the presence of antifoam A, were treated with NaBH(4) in HCl medium to obtain the corresponding hydrides, and AFS measurements were processed in front of external calibrations prepared and measured in the same way as samples. Re…
Are the Recommended Dietary Allowances for Vitamins Appropriate for Elderly People?
2015
Background: An adequate vitamin intake is essential for a good nutritional status, especially in older women, who are more sensitive to nutritional deficiencies. The American, European and Italian Recommended Dietary Allowances (RDAs) derive mainly from studies on adults, and it is not clear whether they also apply to elderly people. Comparing the RDAs with the actual vitamin intake of a group of healthy older women could help to clarify the real needs of elderly people. Objective: Our aim was to compare the American, European, and Italian RDAs with the actual vitamin intake of a group of healthy older women. Design: This was a cross-sectional study. Participants: The study included 286 hea…
Electrochemical detection of dopamine with negligible interference from ascorbic and uric acid by means of reduced graphene oxide and metals-NPs base…
2021
Abstract Dopamine is an important neurotransmitter involved in many human biological processes as well as in different neurodegenerative diseases. Monitoring the concentration of dopamine in biological fluids, i.e., blood and urine is an effective way of accelerating the early diagnosis of these types of diseases. Electrochemical sensors are an ideal choice for real-time screening of dopamine as they can achieve fast, portable inexpensive and accurate measurements. In this work, we present electrochemical dopamine sensors based on reduced graphene oxide coupled with Au or Pt nanoparticles. Sensors were developed by co-electrodeposition onto a flexible substrate, and a systematic investigati…
The new 5- or 6-azapyrimidine and cyanuric acid derivatives of L-ascorbic acid bearing the free C-5 hydroxy or C-4 amino group at the ethylenic space…
2011
Abstract We report on the synthesis of the novel types of cytosine and 5-azacytosine (1–9), uracil and 6-azauracil (13–18) and cyanuric acid (19–22) derivatives of l -ascorbic acid, and on their cytostatic activity evaluation in human malignant tumour cell lines vs. their cytotoxic effects on human normal fibroblasts (WI38). The CD spectra analysis revealed that cytosine (5 and 6), uracil (14–16), 6-azauracil (17) and cyanuric acid (21) derivatives of l -ascorbic acid bearing free amino group at ethylenic spacer existed as a racemic mixture of enantiomers, whereas L-ascorbic derivatives containing the C-5 substituted hydroxy group at the ethylenic spacer were obtained in (4R, 5S) enantiomer…
Investigation of Different Iontophoretic Currents Profiles for Short-Term Applications in Cosmetics.
2018
[EN] This study aimed at investigating the effect of electrical current profile upon the iontophoretic transport of (i) ascorbic acid (AA) and (ii) ellagic acid (EA), into porcine skin in vitro, and the impact of the physicochemical properties of both actives on their mechanism of transport when formulated in cosmetic compositions. The experiments were performed using a proprietary iontophoretic device containing a roller to apply the formulation. Three current profiles were tested: (i) galvanic direct current (DC), (ii) square unipolar pulse current (SPC), and (iii) galvanic direct current (DC) + pulse current (PC). The skin samples were collected at different sampling points, extracted an…
Biochemical indicators for novel forest decline in spruce
1998
Abstract The impact of air pollution on 24 stands of spruce trees in several regions in Germany was investigated. We looked for evidence of biochemical and physiological change at the level of the photosynthetic thylakoid membranes as well as for changes in the antioxidative system in two year old needles. We observed that, as the chlorophyll content decreases in the needles, the amoung of D1 protein declines far more rapidly in relation to the redox components P700 and cytochrome f. Consequently, the PSII/PSI stoichiometry keeps dropping to pregressively lower, meaning unfavorable, values at the chlorophyll content diminishes. This is particularly the case in the higher elevation character…
A green way to gamma-lactams through a copper catalyzed ARGET-ATRC in ethanol and in the presence of ascorbic acid
2011
Abstract A ‘green’ ARGET-ATRC, for the CuCl[PMDETA] catalysed cyclo -isomerization of N -allyl-α-polychloroamides to γ-lactams is described. The process works efficiently (yields 78–96%), uses a bio-solvent, as ethanol, and exploits the reducing feature of ascorbic acid to limit, at a low level (2–4%), the amount of catalyst. To preserve the efficacy of the catalytic cycle, addition of Na 2 CO 3 is essential, which quenches the HCl released during the CuCl[PMDETA] regeneration step. Profitable features of the process are: mild reaction temperatures (25–37 °C), relatively short reaction times (usually 5 h) and low solvent volumes (2 mmol of substrate/mL of ethanol). The method, upon stoichio…
Modulation of Solanum tuberosum L. morphogenesis and antioxidative status in a stem explant culture by limitation of gas exchange: Putative effects o…
2000
Summary The main objective of the present study was to test the hypothesis that increased concentrations of ethylene under conditions of limited gas exchange during in vitro cultivation of potato ( Solanum tuberosum L.) stem explants may lead to increased capaciry of antioxidative defense. By varying the tightness of closure and application of inhibitors of ethylene biosynthesis it was possible to accumulate various concentrations of ethylene in the internal atmosphere of culture flasks, which depended on excision-stress induced ethylene biosynthesis. In tightly closed cultures inhibition of linear growth, promotion of radial expansion and development of an apical hook occurred. Treatment w…