The effects of glycine and L-arginine on heat stability of ginsenoside Rb1.

To identify the effects of amino acids on the heat stability of ginsenoside Rb(1) (Rb(1)), Rb(1) was heat-processed at 120 degrees C with or without glycine or L-arginine. Rb(1) was changed into 20(S)-Rg(3), 20(R)-Rg(3), Rk(1), and Rg(5) by heat-processing through glycosyl elimination and epimerization of carbon-20 by SN1 reaction. Similarly, Rb(1) was changed into 20(S)-Rg(3), 20(R)-Rg(3), Rk(1), and Rg(5) when it was heat-processed with the same amount of glycine, but the generated amount of 20(S)-Rg(3) was higher than when Rb(1) was heat-processed without amino acids, and a significant increase in Maillard reaction products (MRPs) was noted. On the other hand, there were no structural changes in Rb(1) and the generation of MRPs when Rb(1) was heat-processed with the same amount of L-arginine. The improved heat stability of Rb(1) brought about by the addition of L-arginine was thought to be closely related to its characteristics of interfering with nonenzymatic glycation and forming hydrogen bonds with Rb(1).