Vitamin C in plasma: A comparative study of the vitamin stabilized with trichloroacetic acid or metaphosphoric acid and the effects of storage at − 70°, − 20°, 4°, and 25° on the stabilized vitamin

Bradley, Daniel W.; Emery, Gladys; Maynard, James E.

doi:10.1016/0009-8981(73)90158-7

Cited by 48 publications

(25 citation statements)

References 14 publications

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“…The AsA level in Arabidopsis seedlings grown on MS-agar medium for 10 d and on agar for 4 d was determined by the method of Bradley et al (1973) using a vitamin C assay kit (Cosmo Bio).…”

Section: Determination Of Asa Level In Arabidopsismentioning

confidence: 99%

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

et al. 2015

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Humans are unable to synthesize L-ascorbic acid (AsA), yet it is required as a cofactor in many critical biochemical reactions. The majority of human dietary AsA is obtained from plants. In Arabidopsis thaliana, a GDP-mannose pyrophosphorylase (GMPP), VITAMIN C DEFECTIVE1 (VTC1), catalyzes a rate-limiting step in AsA synthesis: the formation of GDP-Man. In this study, we identified two nucleotide sugar pyrophosphorylase-like proteins, KONJAC1 (KJC1) and KJC2, which stimulate the activity of VTC1. The kjc1kjc2 double mutant exhibited severe dwarfism, indicating that KJC proteins are important for growth and development. The kjc1 mutation reduced GMPP activity to 10% of wild-type levels, leading to a 60% reduction in AsA levels. On the contrary, overexpression of KJC1 significantly increased GMPP activity. The kjc1 and kjc1kjc2 mutants also exhibited significantly reduced levels of glucomannan, which is also synthesized from GDP-Man. Recombinant KJC1 and KJC2 enhanced the GMPP activity of recombinant VTC1 in vitro, while KJCs did not show GMPP activity. Yeast two-hybrid assays suggested that the stimulation of GMPP activity occurs via interaction of KJCs with VTC1. These results suggest that KJCs are key factors for the generation of GDP-Man and affect AsA level and glucomannan accumulation through the stimulation of VTC1 GMPP activity.

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“…The AsA level in Arabidopsis seedlings grown on MS-agar medium for 10 d and on agar for 4 d was determined by the method of Bradley et al (1973) using a vitamin C assay kit (Cosmo Bio).…”

Section: Determination Of Asa Level In Arabidopsismentioning

confidence: 99%

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

et al. 2015

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“…AA is the most abundant form in plasma and sensitive to oxidation and degradation during blood sampling, handling, storage, and analysis (Washko et al, 1992;Levine et al, 1999). Various factors such as choice of anticoagulant, temperature, light, pH, dissolved oxygen, solvent, ionic strength, trace metals as ferric ions or the presence of oxidizing enzymes have been reported to affect AA stability (Bradley et al, 1973;Lunec and Blake, 1985;Galan et al, 1988;Margolis and Davis, 1988;Comstock et al, 1995;Key et al, 1996;Margolis and Duewer, 1996;Chung et al, 2001;Ching et al, 2002). It is essential to avoid degradation and oxidation of AA during sampling, sample handling and analysis, as this may skew the ratio between DHAA and AA.…”

Section: Introductionmentioning

confidence: 99%

Stability of whole blood and plasma ascorbic acid

2007

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The objective of this study was to evaluate the impact of pre-analytical factors on the short and long term stability of ascorbic acid (AA), the main form of vitamin C in whole blood and plasma. The effects of various anticoagulants, acidification, storage temperature and time were tested. A recently developed fast and sensitive HPLC method was used to measure AA levels. AA baseline values observed in heparin plasma were significantly higher than values observed in EDTA, citrate and Stabilyte plasma, as well as in serum. pH and temperature were identified as additional critical pre-analytical factors during the short, medium and long term handling and storage. Thus, assessment of reliable and accurate AA status in biological samples demonstrates to be highly dependent on whether the initial conditions during sample handling are controlled. In conclusion, heparin tubes should be used for blood sample collection. As AA is rapidly degraded, sample collection should be followed by immediate centrifugation and plasma acidification. To avoid further degradation during sample handling, samples should be stored at À701C without delay and analyzed within 80 days.

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“…Briefly, salicylic acid was used as a deproteinizing agent, metaphosphoric acid as a stabilizer and amber tubes were used to prevent photoxidation. Samples were stored at -20 ° C for less than 6 days, and plasma ascorbic acid has been shown to be stable under these conditions [33,34] . Certified controls from the National Institute of Standards and Technology (NIST) were used to ensure the validity of the method [35] .…”

Section: Serum Ascorbic Acidmentioning

confidence: 99%

Vitamin C Transporter Gene Polymorphisms, Dietary Vitamin C and Serum Ascorbic Acid

Cahill

El-Sohemy²

2009

Lifestyle Genomics

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Background/Aims: Vitamin C transporter proteins SVCT1 and SVCT2 are required for the absorption and transport of vitamin C in humans. This study aims to determine whether common SVCT genotypes modify the association between dietary vitamin C and serum ascorbic acid. Methods: Non-smoking men and women (n = 1,046) aged 20–29 were participants of the Toronto Nutrigenomics and Health Study. Overnight fasting blood samples were collected to determine serum ascorbic acid concentrations by HPLC and to genotype for two SVCT1 (rs4257763 and rs6596473) and two SVCT2 (rs6139591 and rs2681116) polymorphisms. Results: No diet-gene interactions were observed for the vitamin C transporter polymorphisms, however, the average (mean ± SE) serum ascorbic acid concentrations differed between rs4257763 genotypes (GG: 24.4 ± 1.3, GA: 26.8 ± 1.1, AA: 29.7 ± 1.4 µmol/l; p = 0.002). For this polymorphism, the correlation between dietary vitamin C and serum ascorbic acid was only significant in subjects with a G allele. The SVCT2 polymorphisms also appeared to modify the strength of the diet-serum correlation. Conclusions: Our findings demonstrate that genetic variation in SVCT1 can influence serum ascorbic acid concentrations and that SVCT1 and SVCT2 genotypes modify the strength of the correlation between dietary vitamin C and serum ascorbic acid.

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Vitamin C in plasma: A comparative study of the vitamin stabilized with trichloroacetic acid or metaphosphoric acid and the effects of storage at − 70°, − 20°, 4°, and 25° on the stabilized vitamin

Cited by 48 publications

References 14 publications

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

KONJAC1 and 2 Are Key Factors for GDP-Mannose Generation and Affect l-Ascorbic Acid and Glucomannan Biosynthesis in Arabidopsis

Stability of whole blood and plasma ascorbic acid

Vitamin C Transporter Gene Polymorphisms, Dietary Vitamin C and Serum Ascorbic Acid

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