Determination of potential childhood asthma biomarkers using a powerful methodology based on microextraction by packed sorbent combined with ultra-high pressure liquid chromatography. Eicosanoids as case study

Abstract

Leukotrienes and prostaglandins are arachidonic acid bioactive derived eicosanoids and key mediators of bronchial inflammation and response modulation in the airways contributing to the pathophysiology of asthma. An easy-to-use ultra-high pressure liquid chromatography (UHPLC)-based strategy was developed to characterize biomarkers of lipid peroxidation: leukotrienes E (LTE₄) and B₄ (LTB₄) and 11β-prostaglandin F_2α (11βPGF_2α), present in urine of asthmatic patients (N = 27) and healthy individuals (N = 17). A semi-automatic eVol®-microextraction by packed sorbent (MEPS) was used to isolate the target analytes. Several experimental parameters with influence on the extraction efficiency and on the chromatographic resolution, were evaluated and optimized. The method was fully validated under optimal extraction (R-AX sorbent, 3 conditioning-equilibration cycles with 250 μL of ACN-water at 0.1% FA, 10 extract-discard cycles of 250 μL of sample at a pH of 5.1, elution with 2 times 50 μL of MeOH and concentration of the eluate until half of its volume) and chromatographic conditions (14-min analysis at a flow rate of 300 μL min-1 in an UHPLC-PDA equipped with a BEH C18 column), according to IUPAC guidelines. The findings indicated good recoveries (>95%) in addition to excellent extraction efficiency (>95%) at three concentration levels (low mid and high) with precision (RSDs) less than 11%. The lack-of-fit test, goodness-of-fit test and Mandel's fitting test, revealed good linearity within the concentration range. Good selectivity and sensitivity were achieved with a limits of detection ranging from 0.04 μg L^-1 for LTB4 to 1.12 μg L^-1 for 11βPGF2α, and limits of quantification from 0.10 μg L^-1 for the LTB4 to 2.11 μg L^-1 for 11βPGF2α. The successful application of the fully validated method shows that, on average, the asthmatic patients had significantly higher concentrations of 11βPGF_2α (112.96 μg L^-1vs 62.56 μg L^-1 in normal controls), LTE₄ (1.27 μg L^-1vs 0.89 μg L^-1 in normal controls), and LTB₄ (1.39 μg L^-1vs 0.76 μg L^-1 in normal controls). The results suggest the potential of the target eicosanoids on asthma diagnosis, however, a larger and more extensive study will be necessary to confirm the data obtained and to guarantee a greater robustness to the approach.

Keywords: Asthma; Biomarkers; Eicosanoids; MEPS; UHPLC.