Monomeric dihydroperoxide concentrates from autoxidized methyl docosahexaenoate

An amount of 97% methyl docosahexaenoate (obtained from mackerel pike oil) was prepared, and then its autoxidized products were concd by a countercurrent extraction procedure. By partition chromatography, the autoxidized concs were separated into three fractions. From the first fraction, methyl docosahexaenoate monomeric dihydroperoxide concs were obtained for the first time, though the presence of the dihydroperoxide had been ascertained by the authors before. The dihydroperoxide concs were identified by determining the peroxide value, the mol wt, and UV and IR spectra. From IR data it was confirmed that weak absorptions due toa‐methylene groups and C=C stretching vibrations, respectively, were present in the concs. Thetrans‐trans conjugated diene andcis nonconjugated double bond absorptions appear as relatively strong bands, but thecis‐trans conjugated one is weak. Therefore, the molecules of the concs may have relatively symmetrical structures. The second fraction eluted after the first one contains the products to which the dihydroperoxides have changed on the chromatographic column.