Formation of triacylglycerol core aldehydes during rapid oxidation of corn and sunflower oils with tert-butyl hydroperoxide/Fe2+ |
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Authors: | Olli Sjövall Arnis Kuksis Heikki Kallio |
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Affiliation: | (1) Banting and Best Department of Medical Research, University of Toronto, Charles H. Best Institute, 112 College Street, M5G 1L6 Toronto, Ontario, Canada;(2) Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014, Finland |
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Abstract: | The lipid ester core aldehydes formed during a rapid oxidation (7.8 M tert-butyl hydroperoxide, 90 min at 37°C) of the triacylglycerols of purified corn and sunflower oils were isolated as dinitrophenylhydrazones
by preparative thin-layer chromatography and identified by reversed-phase high-performance liquid chromatography with on-line
electrospray ionization mass spectrometry and by reference to standards. A total of 113 species of triacylglycerol core aldehydes
were specifically identified, accounting for 32–53% of the 2,4-dinitrophenylhydrazine (DNPH)-reactive material of high molecular
weight representing 25–33% of the total oxidation products. The major core aldehyde species (50–60% of total triacylglycerol
core aldehydes) were the mono(9-oxo)nonanoyl- and mono(12-oxo)-9,10-epoxy dodecenoyl- or (12-oxo)-9-hydroxy-10,11-dodecenoyl-diacylglycerols.
A significant proportion of the total (9-oxo)nonanoyl and epoxidized (12-oxo)-9,10-dodecenoyl core aldehydes was found in
complex combinations with hydroperoxy or hydroxy fatty acyl groups (6–10% of total triacylglycerol core aldehydes). Identified
were also di(9-oxo)nonanoylmonoacylglycerols (0.5% of total) and tri(9-oxo)nonanoylglycerols (trace). The identification of
the oxoacylglycerols was consistent with the products anticipated from tert-butyl hydroperoxide oxidation of the major species of corn and sunflower oil triacylglycerols (mainly linoleoyl esters).
However, the anticipated (13-oxo)-9,11-tridecadienoyl aldehyde-containing acylglycerols were absent because of further oxidation
of the dienoic core aldehyde. A significant proportion of the unsaturated triacylglycerol core aldehydes contained tert-butyl groups linked to the unsaturated fatty chains via peroxide bridges (2–9%). The study demonstrates that rapid peroxidation with tert-butyl hydroperoxide consitutes an effective method for enriching natural oils and fats in triacylglycerol core aldehydes
for biochemical and metabolic testing. |
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