Autoxidation of the furan fatty acid ester, methyl 9,12‐epoxyoctadeca‐9,11‐dienoate

The objective of this study was to identify autoxidation products of methyl 9,12‐epoxyoctadeca‐9,11‐dienoate (F 9,12 ). Previous work has shown that F 9,12 is a product both of autoxidation and singlet oxygen oxidation of the methyl ester derivative of conjugated linoleic acid (CLA). F 9,12 , 95% pure, was synthesized from methyl ricinoleate. The synthetic F 9,12 was heated at 50°C in sealed tubes containing air. Each tube contained 6 mg F 9,12 and 1 mg methyl stearate as an internal standard. Samples were taken at 4.5, 7, 23, 46.5, 69.5, and 93 h. The oxidized F 9,12 was dissolved in isooctane and analyzed by gas chromatography (GC), GC‐direct deposition‐Fourier transform infrared spectroscopy, and GC‐electron ionization mass spectrometry. CLA methyl ester was oxidized in a similar manner. Under these conditions, the half‐lives of CLA and F 9,12 were 40 and 35 h, respectively. Oxidation products of F 9,12 that were identified included: 5‐hexyl‐2‐furaldehyde ( I ), methyl 8‐oxooctanoate ( II ), methyl 13‐oxo‐9,12‐epoxytrideca‐9,11‐dienoate ( III ), methyl 8‐oxo‐9,12‐epoxy‐9,11‐octadecadienoate ( IV ), and methyl 13‐oxo‐9,12‐epoxy‐9,11‐octadecadienoate ( V ).