Identification of undescribed medium-chain acylcarnitines present in urine of patients with propionic and methylmalonic acidemias.

In urine of patients with propionyl-CoA carboxylase deficiency or with methylmalonic acidemia, carnitine esters of 2-methyl-branched fatty acids of all chain lengths between 4 and 9 atoms of carbon were identified during the acute phase of the diseases. The chemical structure of these compounds was obtained by gas chromatography-mass spectrometry analysis of their fatty acid moieties in their free and picolinyl ester forms. We suggest mechanisms for the biosynthesis of these branched fatty acids, and their accumulation in urine during episodes of caloric imbalance.

Identification of new medium-chain acylcarnitines present in urine of a patient with medium-chain acyl-CoA dehydrogenase deficiency.

Previously undescribed medium-chain acylcarnitines were identified in a urine sample from a patient with medium-chain acyl-CoA dehydrogenase deficiency. These are the 4-methylvaleryl, 4- and 5-methylhexanoyl, 6-methylheptanoyl-, 6-methyloctanoyl-, 4,5-dimethylhexanoyl- and 4,7-decadienoylcarnitines. Their chemical structures were obtained by gas chromatographymass spectrometry analysis of their fatty acid moieties as picolinyl esters.

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.