Trace-level determination of eight cholesterol oxidation products in human plasma by dispersive liquid–liquid microextraction and ultra-performance liquid chromatography–tandem mass spectrometry

ABSTRACT

7α-Hydroxy cholesterol (7α-OHC), 25-hydroxy cholesterol (25-OHC), 27-hydroxy cholesterol (27-OHC), 4β-hydroxy cholesterol (4β-OHC), 7α-hydroxy-4-cholesten-3-one (7α-C4), 5β-cholestane-3α, 7α, 12α-triol (5β-Triol), cholic acid (CA), and chenodeoxycholic acid (CDCA) are known biomarkers of neurodegenerative diseases. A method for their simultaneous determination in human plasma has been optimized using dispersive liquid–liquid microextraction and ultra-performance liquid chromatography–tandem mass spectrometry. The limits of quantification of the target compounds were in the range of 0.3–3.3 µg/L. The precision achieved by this method was less than 13.4% for intraday and interday analyses. The proposed method was used to analyze eight cholesterol oxidation products in 30 human plasma samples. The analytical results were in a concentration range of 1.6–87.4 µg/L for 7α-OHC, 6.3–58.2 µg/L for 25-OHC, 12.1–98.5 µg/L for 27-OHC, 5.7–64.8 µg/L for 4β-OHC, 1.5–124.1 µg/L for 7α-C4, 0.5–16.5 µg/L for 5β-Triol, 13.1–245 µg/L for CA, and 19.6–487 µg/L for CDCA in the samples. The method may be used for the analysis of biomarkers of neurodegenerative diseases.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biomarker
• cholesterol metabolite
• dispersive liquid–liquid microextraction
• human plasma
• simultaneous determination
• ultra-performance liquid chromatography–tandem mass spectrometry