Oxidative effects of animal‐originated porphyrins and riboflavin on cholesterol oxidation in an aqueous model system

This study was executed to investigate effects of animal‐originated porphyrins and riboflavin on cholesterol oxidation in aqueous model systems. Changes of headspace oxygen contents, cholesterol, and cholesterol oxide products (COP) in the model systems were measured by gas chromatography during storage under light. As concentration of protoporphyrin increased, contents of headspace oxygen decreased and COP increased. The same trend as that of protoporphyrin occurred with riboflavin in terms of contents of headspace oxygen, but production of COP was the highest at 5 ppm riboflavin. As concentrations of hemoglobin and myoglobin increased, headspace oxygen content and COP production were not changed significantly. Consequently, protoporphyrin could be the most active catalyst on the cholesterol oxidation in the aqueous system, but myoglobin and hemoglobin did not accelerate cholesterol oxidation.