Identification of 1,4‐thiomorpholine‐3‐carboxylic acid (TMA) in normal human urine

Abstract
The sulfur‐containing cyclic imino acid 1,4‐thiomorpholine‐3‐carboxylic acid (TMA) has been identified in normal human urine. After the enrichment procedure with ion‐exchange chromatography, the urine extracts were reacted with diazomethane. Gas‐liquid chromatography revealed the presence of two peaks with the same retention times exhibited by authentic TMA after the same derivatization. The two compounds have been identified by mass‐spectrometry as the monomethylated and dimethylated derivatives of TMA. This result represents the first indication of the occurrence of TMA in a mammalian sample.