Development and Validation of a Microplate-based β-carotene Bleaching Assay and Comparison of Antioxidant Activity (AOA) in Several Crops Measured by β-carotene Bleaching, DPPH and ORAC Assays

The reproducibility and reliability of the micro-beta-carotene-linoleic acid bleaching (BCB) assay have been improved, enabling comparison to the antioxidant activity (AOA) of extracts from eleven kinds of crops evaluated by the oxygen radical absorbance capacity (ORAC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. All assays were conducted using 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) as a calibrator, and AOAs were expressed as micromoles of Trolox equivalent per grain of weight. The coefficient variation (CV) of the BCB assay using a microplate was 14.40%, which was comparable to that of the ORAC assay (H-ORAC (14.10%), L-ORAC (18.76%)).