Detection and distribution of arginine derivatives in Panax quinquefolius L. and investigations of their antioxidant properties

Arginyl-fructose (AF) and arginyl-fructosyl-glucose (AFG) are products of the Maillard reaction between arginine and reducing sugars during the thermal treatment of Asian ginseng (Panax ginseng C.A. Meyer). AF and AFG are widely distributed in red ginseng. Because there is no AFG in fresh Asian ginseng, the objective of the present study was to identify the arginine derivatives present in fresh Panax quinquefolius L. Two compounds obtained from P. quinquefolius L. were identified as AF and AFG by comparing the 13C NMR and MS (mass spectrometry) spectra with those of standards. We propose that the Maillard reaction may exist in the fresh plant and not only during the thermal processing of ginseng. The antioxidant activities of AF and AFG were investigated in vitro. The data indicate that the Maillard reaction products AF and AFG contribute to the antioxidant activity of P. quinquefolius L.

► We identified the arginine derivatives (AF and AFG) in dry and fresh Panax quinquefolius L. ► We examined the amounts of arginine derivatives in different parts of P. quinquefolius L. ► AF and AFG were chemically synthesised, and both have free radical-scavenging activity. ► We conclude that the Maillard reaction could exist in the fresh plant.