3-, 6- and 7-Hydroxyoctanoic Acids are Metabolites of Medium-Chain Triglycerides and Excreted in Urine as Glucuronides
✍ Scribed by Costa, Catarina C. G.; Dorland, Lambertus; Kroon, Marijke; Almeida, Isabel Tavares de; Jakobs, Cornelis; Duran, Marinus
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 617 KB
- Volume
- 31
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Three new metabolites of medium-chain fatty acid oxidation, 3-, 6-and 7-hydroxyoctanoyl p-D-glucuronide, were identified in the urine of six infants who were fed a diet enriched in medium-chain triglycerides (MCT). Glucuronides were extracted from the urine by organic solvent extraction with ethyl acetate and by solid-phase extraction on Sep-Pak C,, cartridges. The compounds of interest were also purified from the organic solvent extract by preparative one-dimensional thin-layer chromatography. Cleavage of the glucuronides was achieved by either alkaline hydrolysis or enzymatic hydrolysis with fl-D-glucuronidase. The analyses of the trimethylsilylated derivatives were performed both by gas chromatography with flame ionization detection (GC/FID) and by gas chromatographylmass spectrometry (GC/MS). The structure of the hydroxyoctanoic acids was proved by comparison of their mass spectra with those of reference substances. Authentic 6-hydroxyoctanoic acid was synthesized. The presence of dhydroxyoctanoyl glucuronide shows that in addition to fl-oxidation, co-oxidation and (w -1)-hydroxylation, medium-chain fatty acids can be oxidized at the w -2 position. The conjugation of medium-chain hydroxymonocarboxylic acids with glucuronic acid has not been described in humans before.