Deutsch J C
Department of Medicine, University of Colorado Health Sciences Center, Denver, USA.
Anal Biochem. 1997 Apr 5;247(1):58-62. doi: 10.1006/abio.1997.2035.
The interconversion of ascorbic acid and dehydroascorbic acid was examined in aqueous solution using unlabeled dehydroascorbic acid and nonlabile, stable isotope-labeled ascorbic acid by gas chromatographic/mass spectrometric analysis. Although the formation of unlabeled ascorbic acid from unlabeled dehydroascorbic acid or labeled dehydroascorbic acid from labeled ascorbic acid did not occur to any significant extent when either solutions of unlabeled dehydroascorbic acid or labeled ascorbic acid were incubated alone, significant amounts of both labeled dehydroascorbic acid and unlabeled ascorbic acid formed when unlabeled dehydroascorbic acid was incubated with labeled ascorbic acid at acid pH. At alkaline pH, interconversion did not occur to any appreciable extent. Likewise, interconversion did not appear to occur in plasma at physiologic concentrations of ascorbic acid, but did occur with pharmacologic concentrations. These data show that ascorbic acid and dehydroascorbic acid interconvert in acidic solution, suggesting the reducing hydrogen atoms are delocalized when ascorbic acid is paired with dehydroascorbic acid under these circumstances. Alkaline pH and plasma inhibit the interconversion.
利用未标记的脱氢抗坏血酸和非不稳定、稳定同位素标记的抗坏血酸，通过气相色谱/质谱分析，在水溶液中研究了抗坏血酸和脱氢抗坏血酸的相互转化。当单独孵育未标记的脱氢抗坏血酸溶液或标记的抗坏血酸溶液时，未标记的脱氢抗坏血酸生成未标记的抗坏血酸或标记的抗坏血酸生成标记的脱氢抗坏血酸的情况均未显著发生，但当未标记的脱氢抗坏血酸与标记的抗坏血酸在酸性pH下孵育时，会生成大量的标记脱氢抗坏血酸和未标记抗坏血酸。在碱性pH下，相互转化未达到任何可观的程度。同样，在生理浓度的抗坏血酸条件下，血浆中似乎不会发生相互转化，但在药理浓度下会发生。这些数据表明，抗坏血酸和脱氢抗坏血酸在酸性溶液中相互转化，这表明在这些情况下，当抗坏血酸与脱氢抗坏血酸配对时，还原氢原子是离域的。碱性pH和血浆会抑制这种相互转化。
