A new thiobarbituric acid (TBA) method for determining free malondialdehyde (MDA) and hydroperoxides selectively as a measure of lipid peroxidation

Abstract

A new thiobarbituric acid (TBA) method for selectively determining free malondialdehyde (MDA) and lipid hydroperoxides is described. Partitioning of MDA and hydroperoxides in a Bligh and Dyer extraction was studied with pure substances. It was shown that MDA was present in the methanol‐water phase exclusively, and the hydroperoxides (polar as well as nonpolar) were found in the chloroform phase. Therefore, the TBA test on these phases determines MDA directly present in the sample and the MDA formed during a ferric ion‐catalyzed cleavage of hydroperoxides, respectively. The MDA present in the methanol‐water phase was not bound to amino groups. Hydroperoxide values obtained with the present method corresponded well with a colorimetric determination of peroxides and showed better linearity for higher amounts of hydroperoxides. The possibility of using an iron chelator for preventing hydroperoxide cleavage during the TBA reaction, making the determination selective for MDA without Bligh and Dyer extraction, was investigated. The iron chelator did not completely inhibit peroxide cleavage; therefore, it is necessary to perform the extraction before the TBA determination. The method is suitable for samples with low fat content such as cod mince.