The kinetics of the autoxidation of polyunsaturated fatty acids

Abstract

The kinetics of the autoxidation of a series of polyunsaturated fatty acids (PUFA) with increasing degrees of unsaturation and the mono-, di- and triglycerides of linoleate have been studied in homogeneous chlorobenzene solution at 37 C under 760 torr of oxygen. The autoxidations were initiated by thermal decomposition of azo initiators and followed by measuring the rate of oxygen uptake. The rate of chain initiation was determined by the induction period method using alpha-tocopherol as the chain-breaking antioxidant. The measured oxidizabilities of the PUFA are linearly dependent on the number of doubly allylic positions present in the molecule. Thus, the oxidizability of linoleate is 2.03 X 10(-2) M-1/2 sec-1/2, and the value for docosahexaenoate is five times greater, 10.15 X 10(-2) M-1/2 sec-1/2. The rate of autoxidation for all PUFA studied and for the mono- and diglyceride is proportional to the substrate concentration and to the square root of the rate of chain initiation, implying that the autoxidation of these compounds follows the usual kinetic rate law. The autoxidation of the triglyceride is more complex and does not appear to follow the same rate law at all substrate concentrations. This deviation from the usual kinetic rate expression may be due to lipid aggregation at low concentrations of the triglyceride.

Proteins in Human Brain Cortex Are Modified by Oxidation, Glycoxidation, and Lipoxidation

“…Polyunsaturated fatty acids (PUFA) are other third-party molecules. PUFA are molecules very susceptible to the oxidative action of free radicals (11), generating specific reactive aldehydes, such as malondialdehyde or 4-hydroxynonenal, among others (12). These aldehydes could react with proteins, generating also DNPreactive moieties (6).…”

Empirical Study of the Stability of Biodiesel and Biodiesel Blends: Milestone Report

“…This test is similar to a 24-hour storage stability test proposed by Bondioli and coworkers. AL-27070-F (2) Modified ASTM D4625 (3) with air flow without air flow with air flow without air flow filterable insolubles, mg/100 ml replicate 1 This test was performed on duplicate 500-ml samples. A 50-ml aliquot was removed from each bottle at the end of 1 week of storage.…”

“…Eighteen-carbon chains contain one double bond for oleic acid, two for linoleic acid, and three for linolenic acid. The relative oxidation rates for these C18 esters are linolenic > linoleic >> oleic 3 because the di-and tri-unsaturated fatty acids contain the most reactive sites for initiating the auto-oxidation chain reaction sequence. Oxidation rate correlates with the total number of bis-allylic sites (the methylene CH directly adjacent to the two double bonds), not with the total number of double bonds.…”

Increased lipid peroxidation during long-term intervention with high doses of n-3 fatty acids (PUFAs) following an acute myocardial infarction

“…In vitro studies of lipid peroxidation suggest an increased susceptibility to oxidation with increasing number of double bonds in fatty acids (Cosgrove et al, 1987;Liu et al, 1997). However, the impact of n-3 PUFAs supplementation on lipid peroxidation is controversial (Nenseter & Drevon, 1996).…”