Evaluation of free radical scavenging of dietary carotenoids by the stable radical 2,2-diphenyl-1-picrylhydrazyl

Abstract

In order to avoid the interference of compounds with a chromophoric system when the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) method is used, a new measure of the decrease in absorbance at 580 nm was performed (correlation coefficient between absorbance and DPPH· concentration, 0.9979; p < 0.01). The antioxidant effectiveness of dietary carotenes and xanthophylls towards the stable free radical DPPH· was measured. The antioxidant activity expressed as the amount of antioxidant able to reduce the initial DPPH· concentration to 50% (EC50), given in terms of moles of antioxidant per mole of DPPH·, ranged from 0.16 ± 0.01 (lycopene) to 3.29 ± 0.31 (lutein). The parameter antiradical efficiency (AE), which involves the potency (1/EC50) and the time taken to reach the steady state at EC50 (TEC50), was calculated to discriminate carotenoids with no significant difference between their EC50. Comparison of the structures of the carotenoids tested revealed that the scavenging ability towards DPPH· was increased by the length of the effective conjugated double-bond system and was modulated by the addition of chemical groups on the terminal rings (xanthophylls). © 2000 Society of Chemical Industry