When measuring endogenous TBARS levels from tissues of animals(in vitro)the presence of exogenous antioxidants in the tissue is likely to interfere with the TBARS assay to give artificially low values.Such low values do not then reflect protection against peroxidation in vlvo.The type and extent of the reduction in TBARS values depend on the TBARS assay conditions.Firstly there appears to be an initial(probably iron induced) burst of peroxidtion uring homogenisation,which is antiosidant susceptible.In addition added TBARS products are formed during the final heating stage in methods which retain membrane bound reactants throughout the assay,and this step is also suceptible to antioxidant presence.