Identification of Trihydroxy-Octadecenoates Derived from UV Irradiated or Autoxidized Sesame Oil and Methyl Linoleate and Mechanism of Their Formation

Abstract

Four trihy droxy-octadecenoates (T) were separated from sesame oil (SO) and methyl linoleate (ML) subjected to UV irradiation or oxygen bubbling by column and thin-layer chromatography. From the results of IR, NMR, MS and elemental analysis, two out of the four were identified as methyl 9, 10, 13-trihydroxy-11 (trans) -octadecenoates. The remainder methyl 9, 12, 13-trihydroxy-14 (trans) -octadecenoates (in the case of SO, after methylation), and the two compounds in each group were estimated to be stereoisomeric one another. In addition, the mechanism of their formation was clarified using ML and it proved that T were produced from ML through such intermediates as methyl linoleate hydroperoxides (H) and methyl hydroperoxy-epoxy-octadecenoates (E). T was quite stable against UV light and prolonged autoxidation.