Bicyclic ring formation is not necessary for the (auto)oxidation of ascorbic acid.
The oxidation rates of ascorbic acid and several of its derivatives have been examined in order to delineate the role of bicyclic ring formation in the autooxidation of ascorbic acid. The compounds evaluated and their respective oxidation rates at pH 7.4 are in uM X min-1: ascorbate, 0.70; 5 methyl 3,4 dihydroxytetrone, 0.65; D-iso ascorbate, 0.73; and ascorbyl palmitate, 0.64. These data do not support the contention that bicyclic ring formation is required for the oxidation of ascorbic acid because both 5 methyl 3,4 dihydroxytetrone and ascorbyl palmitate, neither of which can form the bicyclic intermediate, have oxidation rates similar to that of ascorbate. Furthermore, evidence is presented which suggests that ionization of the oxygen on C3 of ascorbic acid is an obligatory initial step in ascorbic acid autooxidation.
D001205:Ascorbic Acid / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D010084:Oxidation-Reduction
D001205:Ascorbic Acid