Peroxide Concentrates from Autoxidized Methyl Eicosapentaenoate

Purified methyl eicosapentaenoate at considerably high degree was prepared by saponifying cuttlefish oil, esterifying the obtained fatty acids with methanol, fractionating the esters through urea adducts, distilling in vacuum the esters of highly unsaturated acids, and separating the esters by means of chromatography. It was autoxidized in the dark at 0 to 2°C. Peroxide concentrates from autoxidized methyl eicosapentaenoate were obtained by the countercurrent extraction procedure, in which the autoxidized ester was simultaneously separated from the unoxidized ester. It has the highest peroxide value (m equiv./kg) 1.19×104 of all lipids ever obtained. The ultraviolet and the infrared spectra of the peroxide concentrates were determined. From the ultraviolet spectra, it was proved that the number of conjugated diene per molecule is about 0.5, that the conjugated triene is negligible, there are no conjugated tetraene and pentaene, and that little unsaturated carbonyl groups exist. Dihydroperoxide exists from the results of infrared spectrum and peroxide value, etc. The -_??_=_??_-_??_-_??_=_??_- group probably exists in the peroxide concentrates, because the α-methylene group absorption in the infrared spectra decreased more than that of expected influences due to conjugated dienes, etc. Cis-trans conjugated diene and trans-trans conjugated diene exist, but considerable double bonds remain as cis-nonconjugated forms.