DETERMINATION OF PLASMA PROTEIN-BOUND MALONDIALDEHYDE BY DERIVATIVE SPECTROPHOTOMETRY

We describe a method for the measurement of protein-bound malondialdeh yde with the thiobarbituric acid reaction in human plasma using second -derivative spectrophotometry. Calibration was done by spectrum height measurement from the baseline at 532 nm. The data were compared with those obtained by using conventional absorbance and fluorimetric measu rements. The results were linear from 0.2 to 80 mu mol/l and the detec tion limit was 0.19 mu mol/l. Within-run and between-run precision, ev aluated by analysing pooled normal plasma, were 8 and 14% respectively . The method was tested for the influence of bilirubin, haemoglobin, g lucose, urea, uric acid, sucrose and N-acetyl-neuraminic acid which in terfered in the colorimetric method but not in the technique proposed here. The mean (+/- SD) malondialdehyde concentration determined in 59 healthy blood donors with the new assay was 0.34 (+/- 0.14) mu mol/l. This assay procedure could represent an alternative to high-performan ce liquid chromatography for the measurement of malondialdehyde in bio logical media.