NEW MELANOIDIN-LIKE MAILLARD POLYMERS FROM 2-DEOXYPENTOSES

In the 2-deoxy-D-ribose/methyl 4-aminobutyrate Maillard system a trapp ed N-substituted 2-(hydroxymethyl)pyrrole is one of the major products . However, nontrapped representatives of this type of compound were hi therto not found in other Maillard model systems, indicating their ext raordinary reactivity. Model experiments with 2-deoxy-D-ribose/methyla mine enabled the detection of N-methyl-2-(hydroxymethyl)pyrrole (1) an d some derived linear oligomers (2, 3) as minor components. Consequent ly, 1 was synthesized and its oligomerization studied under very mild acidic conditions. The deformylated dimeric bis(N-methyl-2-pyrrolyl)me thane (2) and trimeric N-methyl-2,5-bis(N-methyl-2-pyrrolylmethyl)pyrr ole (3) were characterized by GC/MS and NMR. Higher regular oligomers up to 6 N-methyl-2-pyrrolylmethyl units as well as corresponding dehyd ro-oligomers up to 12 units were identified by MALDI-TOF-MS. A complem entary experiment starting with N-methyl-2-hydroxy[C-13]methylpyrrole ([(CH2OH)-C-13]-1) confirmed the structure and the oligomerization pat hway. The possible significance of this type of model oligomer for the melanoidin formation in Maillard reactions is discussed. The antioxid ative activity of the isolated dimer and trimer was tested in Fe(III)- thiocyanate and DPPH assays.