Maillard Reaction of Free and Nucleic Acid-Bound 2-Deoxy-D-ribose and D-Ribose with ω-Amino Acids

The Maillard reaction of free and nucleic acid-bound 2-deoxy-D-ribose and D-ribose with ω-amino acids (4-aminobutyric acid, 6-aminocaproic acid) was investigated under both stringent and mild conditions. Without (with) amines 2-deoxy-D-ribose (D-ribose) displays the strongest browning activity, and DNA is much more reactive than RNA. From stringent reaction between 2-deoxy-D-ribose (or DNA) and methyl 4-aminobutyrate, methyl 4-[2-[(oxopyrrolidinyl)methyl]-1-pyrrolyl]-butyrate (12) was identified by GC/MS and NMR as a new 2-deoxy-D-ribose specific key compound trapped by pyrrolidone formation. Levulinic acid-related N-substituted lactames 13-15 were identified as predominant products from DNA with amino acids, whereas RNA paralleled the reaction with D-ribose. α-Angelica lactone (2), a significant degradation product of DNA, and thiols leads under mild conditions to new addition products (e.g., 17 with glutathione). Probable reaction pathways considering activating effects of the polyphosphate backbone of nucleic acids are discussed.