A new method of measuring the antioxidant activity of polyphenols using cumene hydroperoxide.

ABSTRACT

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 micromol/L and 151 micromol/L, respectively. CONCLUSION: We conclude that this CHP/Hb.MB assay is capable of measuring the antioxidant activity of polyphenols.