COMPARISON OF THE FORMATION OF MALONDIALDEHYDE AND THIOBARBITURIC ACID-REACTIVE SUBSTANCES FROM AUTOXIDIZED FATTY-ACIDS BASED ON OXYGEN-CONSUMPTION

Fatty acid having 18 carbon atoms was oxidized at 170-degrees-C in a c losed vessel to measure the oxygen consumption, which was assumed to b e a chemically reliable index for the autoxidation. The yields of malo ndialdehyde (MDA) and 2-thiobarbituric acid-reactive substances (TBA-R S) were compared with the data for oxygen consumption. In autoxidation of oleic acid, the formation of MDA and TBA-RS correlated with the co nsumed oxygen up to the value of 700 mumol/L. When the oxygen consumpt ion exceeded the value, MDA did not increase and TBA-RS tended to decr ease. In autoxidation of linoleic acid, TBA-RS linearly increased with the oxygen consumption up to 2000 mumol/L. MDA also increased with ox ygen consumption up to 700 mumol/L but thereafter reached a plateau. T he yield of MDA from linoleic acid was similar to that from oleic acid . In autoxidation of linolenic acid, the formation of MDA and TBA-RS c orrelated with the oxygen consumption until the value reached 1150 mum ol/L. When the oxygen consumption exceeded that value, MDA and TBA-RS decreased. Neither MDA nor TBA-RS was detected from stearic acid in sp ite of the increase in oxygen consumption up to 2200 mumol/L.