Increase in the free radical scavenging activity of ginseng by heat-processing

To investigate whether or not the radical scavenging activity of ginseng is enhanced by heat processing, we evaluated the scavenging effects of white ginseng (WG), red ginseng (RG, steamed ginseng at 98-100 degrees C) and sun ginseng (SG, steamed ginseng at 120 degrees C) on nitric oxide, superoxide (O2-), hydroxyl (*OH) radicals and peroxynitrite (ONOO-). Heat-treated ginseng (RG and SG) showed better O2-, ONOO- and *OH-scavenging activities than WG. In particular, the radical scavenging activities of SG were stronger than those of RG. Furthermore, we evaluated the radical scavenging activities of maltol, salicylic acid, vanillic acid and p-coumaric acid, known as principal antioxidant components of ginseng, in WG, RG and SG, and also investigated their contents. Of the tested compounds, maltol, vanillic acid and p-coumaric acid exhibited ONOO(-)-scavenging activity. In addition, maltol and p-coumaric acid showed strong *OH-scavenging activity. Moreover, the content of maltol was remarkably increased in a temperature-dependent manner by heat processing, implying that maltol was closely related to the radical scavenging activity of heat-processed ginseng. These findings indicate that SG may act as a free radical scavenger and protect against damage caused by oxidative stress related with these radicals.