title: Stereospecificity of ginsenoside Rg3 action on ion channels.
abstract: Ginsenosides, active ingredients of Panax ginseng, exist as stereoisomers depending on the position of the hydroxyl group on carbon-20; i.e. 20(R)-ginsenoside and 20(S)-ginsenoside are epimers. We have shown previously that the mixture of 20(R)- and 20(S)-ginsenosides regulates ion channel activity. However, it was not clear which epimer was responsible. We investigated the structure-activity relationship of the ginsenoside Rg3 stereoisomers, 20-R-protopanaxatriol-3-[O-beta-D-glucopyranosyl (1-->2)-beta-glucopyranoside], (20(R)-Rg3) and 20-S-proto-panaxatriol-3-[O-beta-D-glucopyranosyl (1-->2)-beta-glucopyr-anoside], (20(S)-Rg3) in regulating voltage-dependent Ca2+, K+ or Na+ channel currents and 5-HT3A and a3b4 nicotinic acetylcholine (nACh) receptor channel currents expressed in Xenopus oocytes. 20(S)-Rg3 but not 20(R)-Rg3 inhibited the Ca2+, K+ and Na+ channel currents in a dose- and voltage-dependent manner. The fact that only 20(S)-Rg3 is active indicates that its hydroxyl group may be geometrically better aligned with the hydroxyl acceptor group in the ion channels than that of 20(R)-Rg3. However, both Rg3 stereoisomers inhibited 5-HT3A and a3beta4 nACh receptor channel currents. These results indicate that the selectivity of action of the Rg3 stereoisomers differs between voltage-dependent and ligand-gated ion channels.
authors.affiliation: Research Laboratory for the Study of Ginseng Signal Transduction and Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Jeong
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Jong-Hoon
authors.initials: JH
authors.lastname: Kim
authors.forename: Byung-Hwan
authors.initials: BH
authors.lastname: Lee
authors.forename: In-Soo
authors.initials: IS
authors.lastname: Yoon
authors.forename: Joon-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
authors.forename: Hyewhon
authors.initials: H
authors.lastname: Rhim
authors.forename: Yangmee
authors.initials: Y
authors.lastname: Kim
authors.forename: Seung-Yeol
authors.initials: SY
authors.lastname: Nah
mesh_terms: D000818:Animals; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D036145:Ginsenosides / Q000737:chemistry* / Q000494:pharmacology*; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D009865:Oocytes / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D005894:Panax / Q000378:metabolism; D018408:Patch-Clamp Techniques; D013237:Stereoisomerism; D014158:Transcription, Genetic; D014982:Xenopus laevis
chemical_list: D018076:DNA, Complementary; D036145:Ginsenosides; D007477:Ions; C097367:ginsenoside Rg3; D010100:Oxygen