Stereospecificity in hydroxyl radical scavenging activities of four ginsenosides produced by heat processing

The activity-guided fractionation of sun ginseng (SG, heat processed Panax ginseng C. A. Meyer at 120 degrees C) was carried out to identify its main active hydroxyl radical ((OH)-O-center dot) scavenging components. As a result, the n-BuOH fraction mainly consisting of ginsenosides showed the strongest activity. Of several ginsenosides of SG, the (OH)-O-center dot scavenging activities of relatively high contents of 20(S)-Rg(3), 20(R)-Rg(3), Rk(1), and Rg(5) were compared. Rg(5) and 20(S)-Rg(3) showed strong (OH)-O-center dot scavenging IC50 values of 0.15 and 0.44 mM, respectively, and these activities were prominently higher than each of their respective isomers. Therefore, stereospecificity exists in the (OH)-O-center dot scavenging activities of ginsenosides produced by heat processing. Especially, the double bond at carbon-20(22) or the OH group at carbon-20 geometrically close to OH at carbon-12 is thought to increase the (OH)-O-center dot scavenging activity of ginsenosides. (c) 2006 Elsevier Ltd. All rights reserved.