High-resolution capillary zone and gel electrophoresis of structurally similar amphipathic glutathione conjugates based on interaction with β-cyclodextrins

The tripeptide glutathoine is a prominent intracellular constituent that provides protection against genotoxic and carcinogenic electrophiles and is also a component of several biological signal substances. Glutathione conjugates, free glutathione, and glutathione disulfide contain charged amino acids residues, which contribute to solubility in aqueous media. However, the amphipatic nature of glutathione conjugates and the small differences that may distinguish the S substituenys, pose analytical problems in their resolution. The present study demonstrates how homologus S-alkyl and S-benzyl conjugates of high structural similarity can be efficiently resolved by capillary electrophoresis. Inclusion of beta-cyclodextrins in the buffer or in a polyocrylamide gel affords baseline separation of the analytes, The separation methods described are applicable to enzyme assays in vitro and to the identification and quantification of glutathione conjugates of importance in toxicology and physiology. The contribution of beta-cyclodextrin to the separation is primarily based on interactions between its hydrophobic cavity and the S-alkyl and S-benzyl groups of the analytes.