Identification of new medium-chain acylcarnitines present in normal human urine

Analysis of urinary medium-chain acylcarnitines extracted on C18 cartridges and gas chromatography mass spectrometry of their fatty acid moieties as picolinyl esters allowed the determination of the chemical structure of previously unidentified acylcarnitines in normal human urine. These are the 2,6-dimethylheptanoyl-, the 2,6-dimethyl-5-heptenoyl-, and the trans- and cis-3,4-methylene heptanoylcarnitines, also named 3-cyclopropane octanoylcarnitines. Assessment of the structure of these cyclopropane derivatives was obtained by 1H and 13C nuclear magnetic resonance spectroscopy. In addition, other acylcarnitines were tentatively identified.