Journal of Lipid Research, Vol 30, 1611-1619, Copyright © 1989 by Lipid Research, Inc.
Identification of isomeric unsaturated medium-chain dicarboxylic acids in human urine
SJ Jin and KY Tserng
Research Service, Veterans Administration Medical Center, Cleveland, OH 44106.
Dicarboxylic aciduria caused by enhanced or inhibited fatty acid metabolism
is usually described as increased urinary excretion of saturated
medium-chain dicarboxylic acids, such as adipic, suberic, and sebacic
acids. Besides these saturated acids, increased excretion of unsaturated
dicarboxylic acids is also observed. However, the structural identities of
these unsaturated dicarboxylic acids are largely unknown. Using synthetic
authentic samples, dual capillary column gas-liquid chromatography, and
capillary column gas-liquid chromatography-mass spectrometry, we have
identified these acids as trans-2-hexenedioic, trans-3-hexenedioic,
cis-3-octenedioic, cis-4- octenedioic, and trans-3-octenedioic acids. The
mass fragmentation pathways of these compounds (as trimethylsilyl
derivative) are described. We speculate that the metabolic origin of
cis-3-octenedioic acid is oleic acid through the intermediate
cis-5-decenedioic acid. We also propose that cis-4-octenedioic acid is
derived from linoleic acid. The metabolic origin of trans-3-octenedioic
acid is less certain. Since no corresponding cis-hexenedioic acid could be
detected in urine, the metabolic degradation of unsaturated dicarboxylic
acids appears to terminate at octenedioic acid. Trans-2-hexenedioic acid is
probably derived from dehydrogenation of adipic acid.
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