MODIFIED THIOBARBITURIC ACID ASSAY FOR MEASURING LIPID OXIDATION IN SUGAR-RICH PLANT-TISSUE EXTRACTS

Use of the thiobarbituric acid (TBA) assay for thiobarbituric acid-reactive substances (TBARS) of lipid oxidation in extracts of plant materials was examined. Sucrose, fructose, glucose, lactose, citrus pectin, and bovine serum albumin (BSA) interfered with the TBA assay reaction. To correct for the interference caused by sugars (the major interference), a modified procedure was developed using standard curves for both malondialdehyde (MDA) and sucrose. Molar absorbance (MA) of adducts from TBA-MI)A and TBA-sucrose reactions increased when the acidity in the reaction mixture increased and the time of heating and the temperature of heating for the reaction increased. Visible absorbance spectra showed that the adducts from the TBA-sucrose reaction were a mixture of at least two components. Comparisons between the basic and modified procedures indicated that the modified procedure was a more accurate measurement of TBARS of lipid oxidation in apple peel, tomato and pepper fruits, and tomato leaves.