Abstract
We recently demonstrated that exposure of synthetic mono-and diunsaturated triacylglycerols to tert-butylhy-droperoxide (TBHP) leads to formation of stable adducts of the oxidizing agent and the unsaturated esters (Sjövall, O., Kuksis, A., and Kallio, H., Reversed Phase High-Performance Liquid Chromatographic Separation of tert-Butyl Hydroperoxide Oxidation Products of Unsaturated Triacylglycerols. J. Chromatogr. A 905, 119–132, 2001). In the present study we isolated and identified the TBHP adducts of corn oil triacylglycerols. The much wider range of molecular species available in the corn oil permitted us to demonstrate that the yield of the adducts varies with the degree of unsaturation of the triacylglycerol. The highest yields were obtained for the linoleate (20% of linoleoyl-containing residual triacylglycerols) and the lowest ones for the oleate (5% of oleoyl-containing residual triacylglycerols) tria-cylglycerols, whereas the saturated triacylglycerols did not give TBHP adducts in readily detectable amounts. Normal-phase thin-layer chromatography along with reversed-phase high-performance liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization was used to isolate and separate the major molecular species of polyunsaturated triacylglycerols and corresponding TBHP adducts. As an extreme example, the dilinoleoylmonooleoylglycerol was identified as the mono-, di-, tri-, tetra-, and penta-TBHP adduct. LC/MS with electrospray ionization at elevated capillary exit voltage (pseudo tandem mass spectrometry) was used to confirm structures of the [M−RCOOH]+ ions and the absence of TBHP adducts of [M−RCOOH]+. It is concluded that stable adduct formation is an unavoidable complication of preparation of oxotriacylglycerols by oxidation with concentrated TBHP solutions and care must be taken to resolve the adducts from the desired oxidation product.
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Abbreviations
- 16∶0:
-
palmitic acid
- 18∶0:
-
stearic acid
- 18∶1:
-
oleic acid
- 18∶2:
-
linoleic acid
- 18∶3:
-
linolenic acid
- 20∶0:
-
arachidic acid
- CapEx 300:
-
capillary exit voltage of 300 V
- DNPH:
-
2,4-dinitrophenylhydrazine
- ELSD:
-
evaporative light-scattering detector
- ESL:
-
electrospray ionization
- HPLC:
-
high-performance liquid chromatography
- LC:
-
liquid chromatography
- M:
-
molecular ion
- MS:
-
mass spectrometry
- Rt:
-
retention time
- TBHP:
-
tert-butyl hydroperoxide
- TCN:
-
theoretical carbon number
- TLC:
-
thin-layer chromatography
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Sjövall, O., Kuksis, A. & Kallio, H. Analysis of molecular species of peroxide adducts of triacylglycerols following treatment of corn oil with tert-butyl hydroperoxide. Lipids 36, 1347–1356 (2001). https://doi.org/10.1007/s11745-001-0851-0
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DOI: https://doi.org/10.1007/s11745-001-0851-0