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 °C) was carried out to identify its main active hydroxyl radical ( OH) scavenging components. As a result, the n-BuOH fraction mainly consisting of ginsenosides showed the strongest activity. Of several ginsenosides of SG, the OH scavenging activities of relatively high contents of 20(S)-Rg3, 20(R)-Rg3, Rk1, and Rg5 were compared. Rg5 and 20(S)-Rg3 showed strong OH 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 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 scavenging activity of ginsenosides.