Abstract
Authors previously reported that β-glycerylphosphoric acid (β-GP) exhibits antioxidant activity in methyl oleate but it does not decompose hydroperoxides. This report deals further study to elucidate mechanism for inhibition of autoxidation of unsaturated fatty acid esters by phosphate esters.
Trimethyl, triethyl and tributyl phosphate (TBP) and β-GP were found as active in unsaturated fatty acid esters at a concentration range from 0.01 to 0.04%. Hexane solutions of methyl linoleate containing the same concentrations of TBP or β-GP showed a new absorption peak at 230 mμ, and the absorbancy at this peak tended to decrease as the concentration of the phosphate esters increased. Furthermore, another absorption bands at 34003350, 1929, 1090, 1050 cm-1 and 880 cm-1 were observed in the infrared region. The results appear to indicate that an interaction of the PO group of the phosphate esters possibly with the α-methylene group of the methyl linoleate molecule results in perturbation of the ir electrons of the double bonds of the latter. Therefore, a possible mechanism for the observed antioxidant activity of these esters involves either such an interaction or the formation of an unstable oil-soluble product as a result of such an interaction in early stages of autoxidation, rather than decomposition of hydroperoxides as has generally' been regarded for, the phosphate esters.
