Thiobarbituric acid-reactive substances from peroxidized lipids.

Area of Science:

• Biochemistry
• Analytical Chemistry
• Food Science

Background:

• Lipid peroxidation generates reactive aldehydes, including malonaldehyde.
• The thiobarbituric acid (TBA) assay is commonly used to detect malonaldehyde as a marker of lipid peroxidation.
• Previous studies suggest potential interferences and limitations in the TBA assay's specificity.

Purpose of the Study:

• To investigate the reactivity of various peroxidized lipid substances with thiobarbituric acid (TBA).
• To compare different reaction conditions for TBA assay sensitivity and specificity.
• To identify aldehyde species contributing to TBA reactivity beyond malonaldehyde.

Main Methods:

• Performed the TBA reaction on linoleic acid 13-monohydroperoxide, autoxidized fatty esters, edible fats/oils, and lipids from rat liver microsomes and human erythrocyte ghosts.
• Utilized a one-step (100°C) and a two-step (5°C then 100°C) reaction mode.
• Quantified TBA-reactive products using absorbance, fluorescence intensity, and high-performance liquid chromatography (HPLC).
• Assessed the impact of t-butyl hydroperoxide addition on pigment formation.

Main Results:

• TBA reaction yielded significantly higher amounts of the malonaldehyde-TBA adduct than direct malonaldehyde analysis.
• The two-step reaction mode produced slightly higher pigment yields than the one-step mode.
• Addition of t-butyl hydroperoxide dramatically increased pigment yields, particularly for alkenals and alkadienals, but not for malonaldehyde.
• These findings suggest that TBA reactivity in peroxidized lipids involves aldehydes other than malonaldehyde.

Conclusions:

• The TBA assay may overestimate malonaldehyde content in peroxidized lipids due to reactivity with other aldehyde species.
• Reaction conditions, such as the two-step mode and oxidizing agents, can influence TBA adduct formation.
• Further investigation is needed to fully characterize TBA-reactive substances in lipid peroxidation.