Abstract
Abstract 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.
Highlights
The formation, metabolism and elimination of methylated argininesArginine is a conditional essential amino acid and is involved in many important biological processes
Many measurement methods have been developed for asymmetric dimethylarginine (ADMA) and related metabolites in the process until today, various difficulties have been encountered in the measurement of these analytes
ADMA and L-N-monomethyl arginine (L-NMMA) reduce the production of nitric oxide (NO) by inhibiting the nitric oxide synthase (NOS) enzyme, while symmetric dimethylarginine (SDMA) inhibits the uptake of arginine, the substrate of this enzyme, into cells
Summary
Arginine is a conditional essential amino acid and is involved in many important biological processes. Studies have reported that ADMA levels increase in diseases such as Alzheimer [19] and Parkinson [26] This condition is thought to be related to impaired cerebral circulation and vascular endothelium dysfunction, its exact mechanism has not been elucidated yet. Many measurement methods have been developed for ADMA and related metabolites in the process until today, various difficulties have been encountered in the measurement of these analytes These difficulties are result from not well retained in conventional RP columns due to being polar compounds, difficult to separate due to their physicochemical and structural similarities, differences in plasma concentrations, lack of chromophores that enable their specific determination, thermally unstable and non-volatile compounds. Determination of amino acids with sufficient sensitivity and selectivity in UV detectors is very difficult, and it is not possible to define ADMA, SDMA, arginine with HPLC-UV detector. Table : HPLC methods published for measurement of ADMA and related metabolites
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