A COMPARATIVE-EVALUATION OF THIOBARBITURIC ACID METHODS FOR THE DETERMINATION OF MALONDIALDEHYDE IN BIOLOGICAL-MATERIALS

A comparative evaluation was made of the conventional spectrophotometr ic procedure and three published high performance liquid chromatograph ic (HPLC) procedures for the determination of malondialdelyde (MDA) as the thiobarbituric acid (TBA) derivative when applied to liver, fish meal, serum, and urine. Except for urine, spectrophotometric analysis overestimated MDA content. Purification of the TBA-MDA complex obtaine d from liver and fish meal on reverse phase cartridges was found to en tail a loss of complex bound to residual peptides in the trichloraceti c acid (TCA) extract. Mincing as opposed to homogenizing liver samples led to a doubling of values for MDA content. Hexanal was a major TBA reactant, in addition to MDA, in all the samples. Acid hydrolysis and heat were necessary for the release of MDA bound to the amino groups o f proteins and other amino compounds. Methods for free MDA have limite d application to biological materials except short term in vitro prepa rations such as peroxidizing microsomes, in which free MDA accumulates . On the basis of these and other observations, a modified HPLC proced ure for the determination of MDA as the TBA-MDA complex is proposed.