Summary
Detectable levels of four free D-amino acids (phenylalanine, tyrosine, tryptophan and leucine) were found in human urine. This was accomplished using a liquid chromatographic coupled column (i.e., achiral-chiral) method that was developed for the rapid and sensitive analysis of these compounds. The technique was tested on a series of commercial L-amino acids. Care was taken to minimize racemization. Trace to percent levels of contaminating D-enantiomers were found in all commercial samples. In urine the D-amino acids ranged from several hundredths of a percent up to percent levels of the corresponding excreted natural L-amino acids. There were no apparent correlations between the amount of amino acids excreted and the relative amount of D-enantiomers present. Currently this study is being expanded to include additional amino acids and a variety of other physiological fluids.
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On leave from Kyung National University in Korea
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Armstrong, D.W., Duncan, J.D. & Lee, S.H. Evaluation of D-amino acid levels in human urine and in commercial L-amino acid samples. Amino Acids 1, 97–106 (1991). https://doi.org/10.1007/BF00808096
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DOI: https://doi.org/10.1007/BF00808096