Biol. Pharm. Bull. 29(4) 750—754 (2006)

as nitric oxide (NO), superoxide anion (O2 ), hydroxyl ( ·OH) radicals and peroxynitrite (ONOO ), are toxic and play an important role in tissue injury. O2 reacts rapidly with NO to produce the more toxic ONOO . In addition, ONOO and its decomposition product, ·OH, contribute to antioxidant depletion, alterations of protein structure and oxidative damage observed in human diseases. Thus, it is important to find safe and effective scavengers of these oxygen radicals for prevention and treatment of oxidative stress-related diseases. Panax ginseng C. A. MEYER is one of the most widely used herbal medicines in the Orient. It has a wide range of pharmacological and physiological actions, such as antiaging, immunoenhancement, antistress and antitumor. Of the two kinds of ginseng, white ginseng (WG), is air-dried ginseng, and red ginseng (RG) is produced by steaming raw ginseng at 98—100 °C for 2—3 h. RG is reportedly more pharmacologically active than WG. These improved biological activities of ginseng result from changes in the chemical constituents that occur during steaming treatment. Ginseng saponins, referred to as ginsenosides, are believed to play a pharmacologically important role. Several investigators have reported new ginsenosides from RG that are not usually found in WG. Recently, a method which can enhance the yield of these RG specific ginsenosides by steaming ginseng at a temperature higher than RG has been developed. This heat-processed ginseng, termed sun ginseng (SG), has been reported to have more potent pharmacological activities, such as vasorelaxation, antioxidant and antitumor activities. In our preliminary study, SG also showed better NO-scavenging activity than conventional WG and RG. However, almost all ginsenosides had no effects on radical scavenging activity (data not shown). It is insufficient to explain the various pharmacological effects of ginseng with only ginsenosides, especially antioxidant activity related to radical scavenging. Therefore, in this study, we focused on phenolic compounds in ginseng, such as maltol, salicylic acid, vanillic acid and p-coumaric acid, known as principal antioxidant components of ginseng, to investigate the radical scavenging activity of SG. We examined the NO, O2 , ONOO and ·OHscavenging activities of WG, RG and SG. Furthermore, we also studied the radical scavenging activities of maltol, salicylic acid, vanillic acid and p-coumaric acid and the contents of these 4 phenolic compounds in WG, RG and SG.