CHARACTERIZATION OF MODEL TRIACYLGLYCEROL (TRIOLEIN, TRILINOLEIN AND TRILINOLENIN) AUTOXIDATION PRODUCTS VIA HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY COUPLED WITH ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION MASS-SPECTROMETRY

Oxidation products from the autoxidation of three triacylglycerol stan dards have been analyzed using reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to mass spectrometry via an atmospher ic pressure chemical ionization (APCI) source. Triolein, trilinolein a nd trilinolenin were autoxidized in the dark at 50-60 degrees C until the oxidation products represented approximately 30% of the starting m aterial. These oxidation product mixtures were then analyzed using RP- HPLC-APCI-MS. Several classes of oxidation products were directly dete cted and identified. Monohydroperoxides were present in the largest am ounts in the oxidation products mixtures. The hydroperoxides were foun d to provide several structurally useful fragments: epoxide intermedia tes were formed which then underwent further fragmentation, and other fragments were formed from concerted loss of the hydroperoxide group t o form a site of unsaturation. Fragments formed by intra-annular cleav age of epoxide intermediates allowed identification of several hydrope roxide isomers. Bishydroperoxides were observed which underwent simila r fragmentation pathways. Mono- and diepoxides were also formed by the autoxidation reaction. Two classes of epoxides were observed: those i n which an epoxide formed in place of an existing double bond, and tho se in which an epoxide formed away from a double bond. Two distinct fr agmentation mechanisms were observed for epoxides which were not forme d across a double bond. Other oxidation products which were observed i ncluded hydroxy trilinolenin, epidioxy trilinolenin and hydroperoxy, e pidioxy trilinolenin. (C) 1998 Published by Elsevier Science B.V. All rights reserved.