The Chemical and Hydroxyl Radical Scavenging Activity Changes of Ginsenosides Induced by the Maillard Reaction

The root of ginseng, Panax ginseng, has been heat-processed to improve its medicinal efficacy in Korea. Ginsenosides have been regarded as the main active components responsible for the pharmacological activities of ginseng. Although the Maillard reaction is known as a major source of compounds related to enhanced antioxidant activity by heat treatment in various crude drugs or foods, the chemical and free radical scavenging activity changes of ginsenosides brought about by the Maillard reaction have not yet been elucidated. To demonstrate the Maillard reaction of ginsenosides by heat-processing in ginseng, we heat-processed the two ginsenosides Rb1 and Rb2 with glycine as an amino acid, and the hydroxyl radical (•OH) scavenging activity was measured with an electron spin resonance spectrometer. Rb1 and Rb2 were gradually changed into 20(S)-Rg3, 20(R)-Rg3, Rk1, and Rg5 by heat-processing, and the sugar moieties at carbon-20 were separated. The •OH scavenging activities of 20(S)-Rg3 and Rg5 were stronger than that of Rb1, but 20(R)-Rg3 and Rk1 showed weak or no •OH scavenging activities. The generation of Maillard reaction products, although limited to the reaction between the glucosyl moiety and glycine, were positively correlated with the •OH scavenging activity. However, certain amino acids such as Larginine block the structural change of ginsenosides, leading to a stronger •OH scavenging activity. Based upon chemical and •OH scavenging activity tests using Maillard reaction model experiments, the scientific evidence underlying the increase in free radical scavenging activity of ginseng induced by heat-processing was elucidated. _____________________________________________________________________________________________________________