Browning Reaction of Dehydroascorbic Acid with Nucleotides and Their Constituents, Especially with Adenine or Adenosine

Abstract

Dehydroascorbic acid (DHA) was heated with nucleotides, nucleosides or bases in 0.01 N HCl at 98°C for 8 hr, and the browning of the reaction mixture was measured at 480 nm. Of five nucleotides, five nucleosides and four bases examined, browning was relatively strong with 5'-adenylic acid, 5'-guanylic acid, adenosine, guanosine and adenine.
When DHA (1 mmol) was heated with adenine or adenosine (1 mmol) in 4ml of glacial acetic acid or a mixture of glacial acetic acid and methanol, a reaction product (Rf 0.16 fraction or Rf 0.14 fraction)of DHA with adenine or adenosine was formed and separated by thin-layer chromatography. These fractions were visible under UV light and were positive to ammoniacal AgNO₃. The Rf 0.14 fraction was also positive to aniline phthalate. By heating in 2 N HCl at 98°C, the Rf 0.16 fraction or Rf 0.14 fraction yielded adenine, DHA (enol) and a degradation product of DHA or adenosine, adenine, ribose, DHA (enol) and a degradation product of DHA. Also, the peak at 316nm (Rf 0.16 fraction) or shoulder at 305nm (Rf 0.14 fraction) in their UV spectra disappeared. Glycine was formed from these fractions by acid hydrolysis, suggesting that these fractions involved an adenine moiety. From these findings, DHA was found to react with adenine or adenosine to form the reaction product.