Demonstration of Antioxidant and Anti-inflammatory Bioactivities from Sugar-Amino Acid Maillard Reaction Products

Maillard reaction products (MRPs), both crude and fractionated, were assessed for antioxidant potential using cell-free, in vitro 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, Fenton reaction induced deoxyribose degradation and oxygen radical absorbance capacity fluorescein (ORAC(FL)) chemical assays. All MRPs displayed various affinities to scavenge free radicals generated in different reaction media and using different reactive oxygen species (ROS) substrates. High molecular weight MRPs consistently showed the greatest (P < 0.05) antioxidant potential in chemical assays. Repeating these tests in Caco-2 cells with both reactive oxygen and nitrogen (RNS) intracellular assays revealed that the low molecular weight components (LMW) were most effective at inhibiting oxidation and inflammation. In particular, a glucose lysine (Glu-Lys) mixture heated for 60 min had marked intracellular antioxidant activity and nitric oxide (NO) and interleukin-8 (IL-8) inhibitory activities compared to other MRPs (P < 0.05). Further studies employing ultrafiltration, ethyl acetate extraction, and semipreparative high-performance liquid chromatography (HPLC) produced a bioactive fraction, termed F3, from heated Glu-Lys MRP. F3 inhibited NO, inducible nitric oxide synthetase (iNOS), and IL-8 in interferon gamma (IFN-gamma)- and phorbol ester (PMA)-induced Caco-2 cells. F3 modified several gene expressions involved in the NF-kappa B signaling pathway. Two components, namely, 5-hydroxymethyl-2-furfural (HMF) and 5-hydroxymethyl-2-furoic acid (HMFA), were identified in the F3 fraction, with an unidentified third component comprising a major portion of the bioactivity. The results show that MRP components have bioactive potential, especially in regard to suppressing oxidative stress and inflammation in IFN-gamma- and PMA-induced Caco-2 cells.