HPLC and LC-MS/MS measurement methods for the quantification of asymmetric dimethylarginine (ADMA) and related metabolites

Methyl arginine derivatives such as asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), L-N-monomethyl arginine (L-NMMA) are formed by proteolytic catalysis following methylation of arginine residues in proteins. These metabolites reduce NO production. Methylated arginines are an important biomarker for various diseases such as cardiovascular and renal diseases. Therefore, many methods have been developed to reliably and accurately measure the levels of these metabolites. This review, HPLC and LC-MS/MS methods developed for the measurement of methylarginine derivatives are discussed. In HPLC methods, solid phase extraction, derivatization and subsequent separation by reverse phase chromatography were performed. Since these metabolites are polar, they are difficult to retain in conventional reverse phase columns. In addition, as serum levels of these metabolites are low, sensitivity problems have been observed in HPLC methods. Derivatization has been applied to eliminate these problems. However, there have been problems with the stability of derivatives formed. Another important problem is that the separation of stereoisomer ADMA and SDMA can only be achieved chromatographically. Tandem mass spectrometric methods are accurate, selective, sensitive and rapid since analytes are separated depending on m/z ratios rather than chromatographic separation. Therefore, tandem mass spectrometry methods might be considered as the goal standard for these analytes.