Ascorbic acid possesses labile oxygen atoms in aqueous solution

The interaction between ascorbic acid and water was examined using gas chromatographic-mass spectrometric analysis. Structural modifications were analyzed by comparing spectra of tert.-butyldimethylsilyl-derivatized ascorbic acid, [6,6-H-2(2)]ascorbic acid, and [C-13(6)]ascorbic acid with ascorbic acid incubated in O-18-labeled water. The [M-57](+) ion of ascorbic acid readily gained a mass increase of m/z 4 On incubation with labeled water, demonstrating an exchange of two atoms of oxygen. Structural analysis showed this mass increase to occur on carbons 2 and 3. These data indicate that ascorbic acid readily exchanges specific hydroxyl oxygen which may account for some of the prooxidant properties of ascorbic acid in solution. (C) 1998 Elsevier Science B.V.