Increase in antioxidant effect of ginsenoside Re-alanine mixture by Maillard reaction

Ginsenoside Re, one of the major triol type ginsenosides contained in Panax ginseng, has a hydrophobic four-ring steroid-like structure with hydrophilic sugar moieties at carbon-3 and -20. The aim of the present study was to identify the changes in structure and antioxidant activity of ginsenoside Re by the Maillard reaction, which has not been reported yet. The free radical-scavenging activity of ginsenoside Re-alanine mixture was increased by heat-processing. Ginsenoside Re was gradually changed into Rg2, Rg6 and F4 by heat-processing, and the glucosyl moiety at carbon-20 was separated. The improved-free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant Maillard reaction products (MRPs). Antioxidant MRPs were generated from the reaction of glucose and alanine. Based on the viability results of LLC-PK1 renal epithelial cells, MRPs and less-polar ginsenosides contributed to the combined renoprotective effect against oxidative renal damage. Maillard reaction is importantly involved in the increased antioxidant effect of ginsenoside by heat-processing.