Determination of hydrogen peroxide scavenging activity of phenolic acids by employing gold nanoshells precursor composites as nanoprobes

A series of phenolic acids were tested for their ability to scavenge hydrogen peroxide (H2O2) by using a novel enzyme-free, spectrophotometry assay. Gold nanoshells (GNSs) precursor composites were selected as the optical nanoprobes. The approach was based on the H2O2-induced growth of GNSs, which combines nanoscience with food/health research as an innovative detection scheme. The addition of phenolic acids inhibits the formation of complete GNSs and the corresponding peak wavelength changes rationally, which could be used as an optical signature. Among the tested samples, caffeic acid is found to be the most efficient H2O2-scavenger with its H2O2-scavenging activity being 125 x 10(-3) mu M-1, whereas trans-cinnamic acid exhibits the weakest activity (0.73 x 10(-3) mu M-1). Results obtained were considered on the basis of structure-activity relationships. Additionally, several tea and herb extracts were also evaluated. The presented wavelength-based detection method shows superiority in evaluating coloured samples, which avoids background interference compared with the conventional absorbance-based optical methods. (C) 2010 Elsevier Ltd. All rights reserved.