Determination of the antioxidant activity of phenolic compounds by coulometric detection

The combination of reversed-phase high-performance liquid chromatography wi th coulometric detection allows the detection of phenolic antioxidants in c omplex matrices like plant extracts with a high degree of sensitivity and s electivity. According to their voltammetric behaviour, phenolic acids and t ocopherols show maximal detector response at low potentials (100-450 mV) wh ile flavonoids show optimal response at two different potential values tone at 0-300 mV and one at 600-900 mV). The potential corresponding to maximal detector response (MDRP) of phenolic acids was shown to be inversely propo rtional to their antioxidant efficiency as determined in a lipidic model sy stem under strong oxidizing conditions (110 degrees C, intensive oxygenatio n) or by the DPPH. test. However, such a relationship was not observed for flavonoids. (C) 2000 Elsevier Science B.V. All rights reserved.