4-Methyleneglutamic Acid and 4-Methyleneglutamine: Isolation from Extracts of Peanut Seedlings and Determination by High-Performance Liquid Chromatography

Abstract

The non-protein amino acids, 4-methyleneglutamic acid and 4-methyleneglutamine, are isolated from aqueous extracts of peanut seedlings in good yield and high purity using a simple HCl-gradient elution from a column of cation-exchange resin followed, in some instances, by a gradient elution with acetic acid from a column of an anion-exchange resin. All of the 4-substituted glutamic acids commonly found in legume species are resolved by a combination of these two systems. For analytical purposes, resolution of the acidic amino acids as their phenylthiocarbamoyl derivatives is achieved by HPLC but not by conventional ion-exchange amino acid analysis. Although 4-methyleneglutamine undergoes cylic deamidation in acidic medium at a slower rate than glutamine, this reaction occurs to a significant extent at 22°C but not at 4°C during the cation-exchange chromatographic fractionation.