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Clin Chim Acta

Title:		Urine 4-heptanone: a beta-oxidation product of 2-ethylhexanoic acid from plasticisers
Author(s):		Walker V; Mills GA;
Address:		"Department of Chemical Pathology, Southampton General Hospital, Level D, South Block, Mailpoint 6, Tremona Road, Southampton, SO16 6YD, UK. valerie.walker@suht.swest.nhs.uk"
Journal Title:		Clin Chim Acta
Year:		2001
Volume:		306
Issue:		1-Feb
Page Number:		51 - 61
DOI:		10.1016/s0009-8981(01)00390-4
ISSN/ISBN:		0009-8981 (Print) 0009-8981 (Linking)
Abstract:		"4-Heptanone is a common volatile constituent of human urine and is of unknown origin. We hypothesised that it arises from in vivo beta-oxidation of 2-ethylhexanoic acid (EHA) from plasticisers, similar to formation of 3-heptanone from valproic acid. We investigated urine from individuals with normal and increased plasticiser exposure. Using GC/MS, solvent-extracted organic acids were analysed as trimethylsilyl (TMS) derivatives and heptanone with headspace solid-phase microextraction. We identified 3-oxo-2-ethylhexanoic acid, the beta-oxidation product of EHA, as an enol in all samples. This is the first report of its TMS mass spectrum. We also found 2-ethyl-1,6-hexanedioic acid and 5-hydroxyEHA, omega- and omega-1-oxidation products of EHA, respectively, and 2-ethylhexanoylglucuronide, but only in trace amounts in some plasticiser samples. These compounds have not been reported in human urine, nor has the TMS mass spectrum of 5-hydroxyEHA. The median concentrations of 3-oxoethylhexanoic acid and total 4-heptanone of seven plasticiser samples were around 30--175-fold higher than normal samples. 4-Heptanone was barely detectable and 3-oxoethylhexanoic acid was not increased in an eighth plasticiser sample, from a baby with deficiency of 2-methylbranched-chain acyl-CoA dehydrogenase. beta-Oxidation is a major catabolic pathway of EHA in man, and might be involved in the metabolism of other branched-chain drugs and environmental pollutants"
Keywords:		"Caproates/*metabolism Child Environmental Exposure Humans Infant, Newborn Ketones/*urine Male Mass Spectrometry Oxidation-Reduction Plasticizers/*metabolism;"
Notes:		"MedlineWalker, V Mills, G A eng Netherlands 2001/04/03 Clin Chim Acta. 2001 Apr; 306(1-2):51-61. doi: 10.1016/s0009-8981(01)00390-4"