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Characterization of antioxidant and anti-inflammatory activities of Maillard reaction products derived from sugar-amino acid models Chen, Xiumin


Maillard reaction products (MRPs) are produced when reducing sugars react with amino acids, peptides or proteins in heat-processed foods. The overall objective of this research was to isolate and identify MRPs that exhibit antioxidant and anti-inflammatory activities, from different sugar-amino acid model systems comprised of fructose, glucose or ribose, each with glycine (Fru-Gly, Glu-Gly and Rib-Gly) or lysine (Fru-Lys, Glu-Lys and Rib-Lys), respectively. The development of peroxyl radical scavenging activity was found to be positively correlated (r = 0.893-0.905, P < 0.001) with MRPs derived from the intermediate-to-late stages of the reaction and influenced mostly by the type of sugar. The cytotoxicity, antioxidant and anti-inflammatory activities of MRPs were not attributed to the α-dicarbonyl compounds present in the heated mixtures. An in vitro intestinal inflammation model was established using Caco-2 cells stimulated with 8,000U/mL interferon γ (IFN-γ) and 0.1 μg/mL of phorbol myristate acetate (PMA), which induced nitric oxide (NO) through up-regulation of inducible nitric oxide synthase (iNOS) expression and increased interleukin 8 (IL-8) synthesis. The NO and IL-8 inhibitory capacity of MRPs were positively correlated (r = 0.886-0.943, P < 0.05) with intracellular oxidation inhibitory activity. MRPs derived from Glu-Lys heated for 60 min showed the highest inhibitory activity for NO, IL-8, and iNOS among these six model systems and the low molecular weight ultrafiltration fraction recovered from Glu-Lys (GL60FIV, molecular weight (MW) < 1kDa) was attributed to these activities. A fraction recovered from GL60FIV, termed F3, possessed the high NO, iNOS and IL-8 inhibitory activity and was further identified to contain three major sub-fractions (F3-A, F3-B and F3-C). The NO inhibitory capacity of F3-A (IC₅₀, 0.076 mmol/L) was higher (P < 0.05) than that of an iNOS inhibitor, aminoguanidine (IC₅₀, 0.16mmol/L). F3-A had a MW of 191Da and λmax= 370nm. F3-B and F3-C were identified as 5-hydroxymethyl-2-furfural and 5-hydroxymethyl-2-furoic acid, respectively. F3 down-regulated the expressions of genes that were involved in both the NF-κB signaling pathway and peroxidase activities. In conclusion, MRPs isolated from sugar-amino acid model systems can exhibit antioxidative and anti-inflammatory activities that may be useful to reduce intestinal inflammation.

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