Oxygen radical absorbance capacity (ORAC) measurements are widely used to quantify polyphenolic scavenging of radical species, a measure that has been used for a wide range of applications from food preservatives to dietary recommendations for cancer prevention. Recently, however, the validity of ORAC and other radical scavenging assays to evaluate polyphenol antioxidant activity has been questioned. We have determined that iron binding rather than radical scavenging is the primary mechanism for polyphenol prevention of oxidative DNA damage, both in vitro (IC50 values of 1-59 µM) and in E. coli (IC50 values of 3-100 µM). This antioxidant activity can be predicted for a variety of polyphenolics using calculated pKa and hydrophobicity values, thus enabling identification of more effective polyphenolic compounds as dietary supplements and food preservatives.

Beyond ORAC: Dietary polyphenolics as metal-binding antioxidants and food preservatives

249th National Meeting (2015)

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