Gas chromatography–mass spectrometry of cis-9,10-epoxyoctadecanoic acid ( cis-EODA) : II. Quantitative determination of cis-EODA in human plasma

• Published in: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences Analytical technologies in the biomedical and life sciences, 2004-05, Vol.804 (2), p.403-412
• Main Authors: Tsikas, Dimitrios, Mitschke, Anja, Gutzki, Frank-Mathias, Meyer, Hartmut H, Frölich, Jürgen C
• Format: Article
• Language: English
• Subjects: Analysis; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Chromatography, High Pressure Liquid; cis-9,10-Epoxyoctadecanoic acid; Female; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry - methods; General pharmacology; Humans; Male; Medical sciences; Oleic acid; Pharmacology. Drug treatments; Reference Values; Stearic Acids - blood
• ISSN: 1570-0232; 1873-376X
• DOI: 10.1016/j.jchromb.2004.01.055

Cytochrome P450 dependent epoxidation and non-enzymic lipid peroxidation of oleic acid ( cis-9-octadecenoic acid) result in the formation of cis-9,10-epoxyoctadecanoic acid ( cis-EODA). This oleic acid oxide has been identified indirectly in blood and urine of humans. Reliable concentrations of circulating cis-EODA have not been reported thus far. In the present article, we report on the first GC–tandem MS method for the accurate quantitative determination in human plasma of authentic cis-EODA as its pentafluorobenzyl (PFB) ester. cis-[9,10- 2 H 2 ]-EODA ( cis-d 2-EODA) was synthesized by chemical epoxidation of commercially available cis-[9,10- 2 H 2 ]-9-octadecenoic acid and used as an internal standard for quantification. Endogenous cis-EODA and externally added cis-[9,10- 2 H 2 ]-EODA were isolated from acidified plasma samples (1 ml; pH 4.5) by solvent or solid-phase extraction, converted into their PFB esters, isolated by HPLC and quantified by selected reaction monitoring. The parent ions [M–PFB] − at mass-to-charge ratio ( m/ z) 297 for cis-EODA and m/ z 299 for ( cis-d 2-EODA) were subjected to collisionally-activated dissociation and the corresponding characteristic product ions at m/ z 171 and 172 were monitored. In plasma of nine healthy humans (5 females, 4 males), cis-EODA was found to be present at 47.6±7.4 nM (mean±S.D.). Plasma cis-EODA levels were statistically insignificantly different ( P=0.10403, t-test) in females (51.1±3.4 nM) and males (43.1±2.2 nM). cis-EODA was identified as a considerable contamination in laboratory plastic ware and found to contribute to endogenous cis-EODA by approximately 2 nM. The present GC–andem MS method should be useful in investigating the physiological role(s) of cis-EODA in humans.