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

Abstract

Fish and algae oil supplements are enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are precursors to oxidized fatty acids, known as oxylipins. Here, we optimized a base hydrolysis method for measuring oxylipins in oil with ultrahigh-performance liquid chromatography coupled to tandem mass-spectrometry (UPLC-MS/MS) and quantified them in fish and algae oil supplements. Hydrolysis of 2 μL of oil with sodium carbonate resulted in greater oxylipin concentrations and minimal matrix effects, compared to higher oil volumes (10, 20, and 30 μL). Oxylipin yield was higher when oil was hydrolyzed in methanol containing 0.1% acetic acid and 0.1% butylated hydroxytoluene, compared to no methanol, and using sodium hydroxide versus sodium carbonate. Oxylipins extracted from 2 μL of oil using sodium hydroxide in solvent showed that EPA-derived oxylipins were most abundant in fish oil (84−87%), whereas DHA-oxylipins were abundant in algae oil (83%). This study shows that fish and algae oils are direct sources of EPA-and DHA-derived oxylipins.

Quantification of Nonpersistent Pesticides in Small Volumes of Human Breast Milk with Ultrahigh Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry

“…Milk is a complex matrix, and its lipid constituents are known to suppress or neutralize the charge of molecular ions at the electrospray mass-spectrometry source through increased viscosity of the nebulized droplet surface, thus inhibiting release of charged ions, complexation with macromolecules, and competition for ionic charge, all effectively lowering the signal reaching the detector (reviewed in ref ). Our findings are in agreement with studies that reported increased recoveries of other analytes (e.g., oxidized lipids) after reducing the sample matrix amount. , …”

“…Our findings are in agreement with studies that reported increased recoveries of other analytes (e.g., oxidized lipids) after reducing the sample matrix amount. 38,41 UPLC−MS/MS analysis revealed the unexpected presence of pesticides in blank LCMS-grade water, extracted in the same manner as the milk (Table 5). A similar background signal was previously reported by Hao et al when pesticides were measured in "nanopure" water on the same type of mass spectrometer used in our study (QTRAP 6500).…”

Effects of Potato Processing and Frying on Oxylipin Concentrations

“…A limitation of the present study is that the hydrolysis of oil and potato/French fries oxylipins was performed using sodium carbonate. Recently, we reported that sodium hydroxide is a better hydrolysis base than sodium carbonate when applied to fish oil, soybean oil and bovine milk. − We did not know this when the samples used in the present study were analyzed. It is likely, therefore, that our absolute oxylipin values in oil and French fries are underestimated, although differences between the groups are not likely to be impacted by the use of sodium hydroxide because the same base hydrolysis conditions were used across all groups.…”

Chronic exposure to traffic-related air pollution reduces lipid mediators of linoleic acid and soluble epoxide hydrolase in serum of female rats

“…J o u r n a l P r e -p r o o f 14 Compounds that used d4-PGE2 as a surrogate standard were not analyzed due to degradation of the deuterated standard during hydrolysis, consistent with previous reports (Emami et al, 2020;Ostermann et al, 2020). The ratio of PUFA diol to precursor epoxides (x 100) was calculated to estimate in vivo sEH activity (Stefanovski et al, 2020).…”