2,5-Dimethyl-1H-pyrrole-3,4-dicarbaldehyde as a new pre-column reagent for amino compounds

Amino acids are critical to life, have a variety of roles in metabolism and are important components or precursors of many biological molecules. Dietary supplements have become an increasingly popular and convenient source of free amino acids. The direct UV detection provides low sensitivity for most amino acids owing to the absence of a strong chromophore or fluorophore group. Therefore, pre- or post-column derivatization is favourably used for their analysis. The aim of the present study is to propose 2,5-dimethyl-1H-pyrrole-3,4-dicarbaldehyde[1] (I) as a new pre-column labelling reagent for the determination of amino acids in dietary supplements. The compound (I) reacts at mild conditions (10 min at ambient temperature in water) with primary amino group giving stable adducts (II). The derivatization conditions were optimized by considering different parameters (temperature, pH and reagent concentration) using L-valine. The reaction was found to be quantitative. The synthesized L-valine, glycine and L-phenylalanine derivatives were characterized by 1H-NMR, IR, UV and optical activity, whereas the adducts obtained by derivatization were separated by LC under reversed-phase conditions and detected at λ=320 nm. The method was applied successfully to the quali-quantitative analysis of commercial polyaminoacid preparations. [1] A. Andreani, A. Cavalli, M. Granaiola, M. Guardigli, A. Leoni, A. Locatelli, R. Morigi, M. Rambaldi, M. Recanatini, A. Roda, J. Med. Chem. 44 (2001) 4011-14.