Formation of Cu or Fe thiobarbiturate complexes interfere with the determination of malondialdehyde

This research was conducted to determine whether or not Cu(II) and Fe(III) form TEA complexes that absorb and fluoresce at the same wavelengths as the bis-TBA-MDA adduct and support a false conclusion that Cu(II) and Fe(III) cause lipid and other tissue component oxidations as evidenced by the appar ent formation of the bis-TBA-MBA adduct. Additions of Cu(II) or Fe(III) to Na TBA gave concentration related increases in absorbance at 532 nm, the wa velength of maximum absorbance of the bis-TBA-MDA adduct. These absorbance spectra demonstrate that the addition of aqueous solutions of Na TEA to sys tems containing added Cu(II) and/or Fe(III) and their butanol extracts will support the false conclusion that Cu(II) and/or Fe(LII) caused lipid and o ther tissue component oxidations. Fluorescence at 553 nm, the maximum for f luorescence of the bis-TBA-MDA adduct, increased as the concentration of Cu (TI) increased but decreased with the addition of Fe(III). Fluorescence obt ained following the addition of Cu(II) to Na TEA will support the false con clusion that Cu(II) causes lipid and other tissue component oxidations whil e the lack of fluorescence following the addition of Fe(III) will not suppo rt this false conclusion. These studies show that the presence of Cu(II) or Fe(III) in TBA assay systems lead to the specious interpretation that oxid ations occurred due to the formation of HO. radical via Cu(II)- or Fe(III)- mediated Fenton chemistry. (C) 1998 Elsevier Science Inc. All rights reserv ed.