Autoxidation of Polyunsaturated Fatty Acids

Abstract

Neat samples of polyunsaturated fatty acids were exposed to ozone in air in a flow system, and the formation of peroxides, conjugated dienes and thiobarbituric acid (TBA)-reactive material was followed as a function of time. The effect of ozone is to shorten the induction period normally observed in autoxidation studies, but the ozone, at the concentrations used here (0-1.5 ppm), appears to have no effect on the rates of product formation after the induction period. During the induction period, increasing ozone concentrations give rise to substantially increased rates of peroxide (or materials which titrate like peroxide) formation, a slightly increased rate of conjugated diene formation, and no significant increase in the rate of production of TBA-reactive material. Vitamin E lengthens the induction period but appears to have no other effect. Some of these data are in conflict with earlier reports of Menzel et al.

Heterogeneous Reactions of Linoleic Acid and Linolenic Acid Particles with Ozone: Reaction Pathways and Changes in Particle Mass, Hygroscopicity, and Morphology

“…However, it must be emphasized that the -scission step is expected to be only a minor decomposition pathway. On the basis of the observations by Pryor et al 27 and our Raman characterizations, it is reasonable to suggest that the autoxidation of linoleic acid and linolenic acid can also be initiated within a short period of time under the ozone concentrations (∼200-250 ppb) used in the current study. The induction periods of these two fatty acids are probably reduced to less than 2 h (or even shorter as the time resolution is not high enough to trace the exact induction periods) if we use the change in the intensity of the product peaks of the conjugated dienes at 1560-1640 cm -1 as the estimations (Figure 7).…”

Fast Transmethylation of Total Lipids in Dried Blood by Microwave Irradiation and its Application to a Population Study

“…Air exposure and humidity are critical variables contributing to instability of PUFA in dried blood samples. Part of the degradation was likely due to ozone, which results in PUFA oxidation when PUFA is exposed to air [32]. By limiting air exposure, even without BHT, the fatty acid profiles in dried blood could be maintained for two weeks at 4 °C in a cellophane envelope within an airtight closure [5].…”

Autoxidation of methyl linoleate initiated by the ozonide of allylbenzene

“…Initiator --2I" I" + RH-) IH + R" [3] number of radicals produced per initiator molecule {assumed to be 2), e is the efficiency of chain reaction ini- [4] tiation and k d is the rate constant for thermal decomposition of initiator (36). Substituting this expression into [5] Figure 4 shows a linear correlation between rates of CD formation and [ABO]'12[18:2 ME]; a similar linear correlation is also found when rates of oxygen-uptake are [7] plotted vs [ABO]'12118:2 ME] (19}.…”

“…Ozonides as a contributor to initiating activity in ozoneinduced autoxidation of 18:2 ME. Our previous work has shown that ozone initiates the autoxidation of 18:2 ME in vitro (4). We also have used an ESR spin-trapping method to show that ozone reacts with olefins {e.g., with 18:2 ME at -78~ to form intermediates that decompose to give radicals starting at about -30~ (7,8}.…”

“…Lung lipids containing polyunsaturated fatty acids {PUFA) are thought to be among the primary targets when air containing ozone is breathed (2,3). We have shown that ozone initiates the autoxidation of PUFA in vitro (4); these peroxidative reactions contribute to the disruption of cell membranes, and thus lead to loss of cellular compartmentalization and cell death (3). Our efforts have been aimed at elucidating the mechanism(s) by which ozone, a non-radical, reacts with PUFA to yield radicals that are capable of initiating peroxidative reactions (4)(5)(6)(7)(8)(9)(10)(11).…”