Simultaneous measurement of foliar glutathione, gamma-glutamylcysteine, and amino acids by high-performance liquid chromatography: comparison with two other assay methods for glutathione.

The recent production of transformed plants with enhanced capacity for glutathione synthesis has highlighted the interactions between foliar glutathione and turnover of free amino acid pools. The development of a convenient method for simultaneous measurement of glutathione, gamma-glutamylcysteine, and 16 amino acids is reported. This method utilizes derivatization of compounds with o-phthalaldehyde in the presence of 2-mercaptoethanol followed by separation using reversed-phase high-performance liquid chromatography. Eluted compounds are detected fluorimetrically. The method was tested using untransformed poplars and poplars in which foliar thiol contents have been enhanced by overexpression of gamma-glutamylcysteine synthetase. Foliar contents of glutathione determined by this method were comparable to those measured in common extracts by two other techniques.