Isolation and characterization of a group of oligopeptides related to oxidized glutathione from the root of Panax ginseng

Abstract

Six γ-glutamyl oligopeptides were isolated for the first time from aqueous methanol extracts of Panax ginseng root by using column chromatography on ion-exchange resin, gel filtration and reverse-phase high- performance liquid chromatography. Their structures had been established with the methods of amino acid analysis, N-terminal, C-terminal determination and double-coupling sequence analysis. They were: P-I (N-γ-glutamylcystinyl- bis-glycine), P-II (γ-glutamylcysteinylglycine disulfide, oxidized glutathione), P-III (N,N'-bis-γ-glutamylcystinylglycine), P-IV (γ- glutamylcysteinylglycinamide disulfide), P-V (N-γ-glutamylglycylcysteine disulfide), P-VI (γ-glutamylarginine); five of them are related to oxidized glutathione. The structures were further confirmed by the chemical synthesis. As far as we know, P-V (N-γ-glutamylglycylcysteine disulfide) is a new biologically active peptide which exhibits somnogenic effect and is more potent than that of P-II.