Targeting esterified oxylipins by LC–MS - Effect of sample preparation on oxylipin pattern

Clinical blood sampling for oxylipin analysis – effect of storage and pneumatic tube transport of blood on free and total oxylipin profile in human plasma and serum

“…In order to evaluate the impact of the transitory storage or PTS transport we used the ACL based on the methodological RSD obtained from quality control plasma samples analyzed in parallel 42 which was in a similar range as previously reported for both, free 34,56 and total oxylipins. 40 Free oxylipins in plasma from whole blood stored at 4°C for 4 h remained almost stable (≥67% of the samples were within the ACL) with exception of samples from a few individuals showing higher deviations for 12-LOX and COX-1 derived products. After 24 h at 4°C besides considerable increase in platelet-derived oxylipins also 15-LOX products were clearly increased.…”

“…free and esterified oxylipins were extracted from 100 µL plasma or serum as described with slight modifications. 40 After addition of 10 µL antioxidant solution and 10 µL IS solution, 400 µL isopropanol was added and samples were stored for 30 min at −80°C for protein precipitation. After centrifugation the supernatant was hydrolyzed (300 µL 1.5 M KOH (75/25, MeOH/water, v/v)), immediately neutralized with 55 µL 50% acetic acid, diluted with 2 mL sodium phosphate buffer ( pH 5.5) and extracted by SPE.…”

Quantitation of Oxylipins in Fish and Algae Oil Supplements Using Optimized Hydrolysis Procedures and Ultra-High Performance Liquid Chromatography Coupled to Tandem Mass-Spectrometry

“…The goal of this experiment was to compare the efficiency of hydrolysis with sodium carbonate to sodium hydroxide, in view of a recent study showing that potassium hydroxide efficiently hydrolyzes bound oxylipins . 27 A stock solution of 500 μL of cod liver oil in 7500 μL of chloroform:methanol (2:1) was prepared, and 32 μL (corresponding to 2 μL of oil) was added to test tubes containing 10 μL of surrogate standard mix and 10 μL of antioxidant mix. The samples were dried under nitrogen and reconstituted in 190 μL of extraction solvent.…”

“…25 In other matrices such as plasma, lowering the sample volume or increasing the base concentration was reported to increase the concentration of oxylipins including epoxy and hydroxy fatty acid metabolites due to improved hydrolysis efficiency. 27 This suggests that similar to plasma, modifying the sample volume (or mass) and base amount may improve oxylipin hydrolysis of oils.…”

Effect of dietary EPA and DHA on murine blood and liver fatty acid profile and liver oxylipin pattern depending on high and low dietary n6-PUFA

“…Moreover, oxylipins can be re-esterified to lipids or conjugated with glucuronic acid 60 and free oxylipins represent only a small fraction of the total oxylipin profile. 61 Other explanations could be an increased degradation/metabolization of EPA derived oxylipins in DHA-fed groups or a limited hepatic formation of EPA oxylipins when DHA is supplemented.…”