Metal-catalyzed peroxidation of polyunsaturated fatty acids.

In this study malondialdehyde (MDA) was measured as the thiobarbituric acid (TBA) adduct by high performance liquid chromatography with linolenic acid (LA), as well as with LA to which the following metal ions were added: Ag+1, Al+3, As+5, Ba+2, Cd+2, Co+2, Cu+1, Cu+2, Fe+2, Fe+3, Hg+2, Mn+2, Ni+2, Pb+2, and Zn+2. Our results showed that Fe+3 is a particularly potent catalyst of this oxidation reaction. Several other metals also significantly increased the production of MDA over LA alone, as shown by the Mann-Whitney test, including Al+3 and Fe+2 (p less than 0.001), Cu+2, Ba+2, Mn+2 (p less than 0.01), and As+5 (p less than 0.05). Pb+2 almost completely inhibited the production of MDA from LA (p less than 0.001). Addition of the free radical scavenger, butylated hydroxytoluene (BHT), significantly inhibited MDA formation in these latter reactions, indicating they are free-radical mediated. Pre-incubation of the reaction mixtures at 37 degrees C and physiologic pH with both Fe+2 and Fe+3 greatly increased MDA formation, suggesting that in acute metal toxicity the initiating free-radical process might be primarily due to direct metal catalysis of preformed lipid peroxides.