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Bicyclic ring formation is not necessary for the (auto)oxidation of ascorbic acid
Biochemical and Biophysical Research Communications
|September 15, 1983
Summary
Bicyclic ring formation is not required for ascorbic acid oxidation. Derivatives like 5-methyl-3,4-dihydroxytetrone and ascorbyl palmitate oxidize similarly to ascorbic acid, suggesting C3 oxygen ionization is key.
Area of Science:
- Biochemistry
- Organic Chemistry
Background:
- Ascorbic acid (Vitamin C) is a vital antioxidant.
- Its autooxidation mechanism, particularly the role of bicyclic intermediates, remains incompletely understood.
Purpose of the Study:
- To investigate the necessity of bicyclic ring formation in ascorbic acid autooxidation.
- To determine the influence of specific structural modifications on oxidation rates.
Main Methods:
- Comparative kinetic analysis of ascorbic acid and its derivatives.
- Measurement of oxidation rates at a controlled pH (7.4).
Main Results:
- Ascorbic acid, 5-methyl-3,4-dihydroxytetrone, D-iso ascorbate, and ascorbyl palmitate exhibited similar oxidation rates (0.64–0.73 uM/min).
- Compounds incapable of forming bicyclic intermediates showed oxidation rates comparable to ascorbic acid.
- Evidence suggests initial ionization of the C3 oxygen is critical for autooxidation.
Conclusions:
- Bicyclic ring formation is not a prerequisite for ascorbic acid autooxidation.
- The autooxidation of ascorbic acid likely initiates with the ionization of the C3 oxygen atom.