Remarkable impact of amino acids on ginsenoside transformation from fresh ginseng to red ginseng.

BACKGROUND

Amino acids are one of the major constituents in , including neutral amino acid, acidic amino acid, and basic amino acid. However, whether these amino acids play a role in ginsenoside conversion during the steaming process has not yet been elucidated.

METHODS

In the present study, to elucidate the role of amino acids in ginsenoside transformation from fresh ginseng to red ginseng, an amino acids impregnation pretreatment was applied during the steaming process at 120°C. Acidic glutamic acid and basic arginine were used for the acid impregnation treatment during the root steaming. The ginsenosides contents, pH, browning intensity, and free amino acids contents in untreated and amino acid-treated samples were determined.

RESULTS

After 2 h of steaming, the concentration of less polar ginsenosides in glutamic acid-treated was significantly higher than that in untreated during the steaming process. However, the less polar ginsenosides in arginine-treated increased slightly. Meanwhile, free amino acids contents in fresh , glutamic acid-treated , and arginine-treated significantly decreased during steaming from 0 to 2h. The pH also decreased in samples at high temperatures. The pH decrease in red ginseng was closely related to the decrease in basic amino acids levels during the steaming process.

CONCLUSION

Amino acids can remarkably affect the acidity of sample by altering the pH value. They were the main influential factors for the ginsenoside transformation. These results are useful in elucidating why and how steaming induces the structural change of ginsenoside in  and also provides an effective and green approach to regulate the ginsenoside conversion using amino acids during the steaming process.