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Updated: Aug 11, 2026
11:56
A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 11, 2014
"Antioxidant" (reducing) efficiency of ascorbate in plasma is not affected by concentration
I F Benzie1, W Y Chung, J J Strain
1Department of Nursing and Health Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China.
The Journal of Nutritional Biochemistry
|November 13, 2004
Summary
Ascorbate (vitamin C) antioxidant efficiency is constant, contrary to previous findings. This study suggests concentration-dependent effects are due to testing methods, not inherent properties of vitamin C.
Area of Science:
- Biochemistry
- Nutritional Science
- Analytical Chemistry
Background:
- Ascorbate (vitamin C) is a key dietary antioxidant.
- Previous studies using indirect methods suggest its antioxidant efficiency decreases with concentration.
- This phenomenon requires further investigation to understand ascorbate's true behavior.
Purpose of the Study:
- To investigate the effect of ascorbate concentration on its antioxidant efficiency.
- To compare results from a direct antioxidant capacity assay with indirect methods.
- To clarify the concentration-dependent behavior of vitamin C.
Main Methods:
- Utilized the ferric reducing/antioxidant power test (FRAP assay), a direct method for assessing antioxidant capacity.
- Tested ascorbate in both pure aqueous solutions and plasma.
- Evaluated ascorbate stability in different solution types (plasma, aqueous, EDTA, heparinized).
Main Results:
- Ascorbate's antioxidant efficiency factor remained constant (2) across a wide concentration range in both plasma and aqueous solutions.
- Higher ascorbate concentrations led to a greater absolute loss of ascorbate over time.
- Ascorbate exhibited lower stability in plasma compared to aqueous solutions and in EDTA-treated plasma versus heparinized plasma.
Conclusions:
- The previously reported concentration-dependent decrease in ascorbate's antioxidant efficiency is likely an artifact of indirect testing methods and ascorbate degradation during assays.
- Ascorbate's inherent antioxidant efficiency is not concentration-dependent.
- The FRAP assay provides a more accurate representation of ascorbate's antioxidant behavior.
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