Background: It is well known that polyphenols lower the risk of chronic
diseases such as heart disease and cancer. We describe a new method using cumene
hydroperoxide (CHP) to determine the antioxidant activity of polyphenols. CHP is
considered to be a model reactive lipid peroxidation product.
Methods: The method was based on two reactions: the reduction of a known
concentration of CHP by polyphenols and the reaction of the remaining CHP with a
methylene blue derivative (10-N-methylcarbamoyl-3,7 dimethylamino-10H-phenothiazine)
in the presence of haemoglobin. Methylene blue was formed as a result of the two
reactions and then measured by absorbance at 675 nm. We named this assay the 'cumene
hydroperoxide/haemoglobin·methylene blue (CHP/Hb·MB) method'. We examined 13
polyphenols and nine compounds known to be antioxidants.
Results: Among the 13 polyphenols, milicetin, with the largest number of
hydroxyl groups, had the highest antioxidant activity, followed by cyanidin,
pelargonidin and quercetin. It is suggested that the increase in the number of
hydroxyl groups induced a higher antioxidant activity. Within-run coefficients of
variation were 3.6% and 3.5% at the mean antioxidant activity of 50 µmol/L and 151
µmol/L, respectively.
Conclusion: We conclude that this CHP/Hb·MB assay is capable of
measuring the antioxidant activity of polyphenols.
