A rapid antioxidant assay based on acidic potassium permanganate chemiluminescence

The total antioxidant capacity of fruit juices and teas was established using flow-injection analysis with acidic potassium permanganate chemiluminescence detection, and the results were compared to those of two conventional assays. The chemiluminescence procedure was rapid (over 100 samples could be run per hour) and precise (relative standard deviation <2.5%). Good agreement between the chemiluminescence and DPPH assays was observed for 20 tea samples (r = 0.955). In general, green teas gave larger responses than black teas with both procedures, but there was considerable variation between brands. Moreover, when coupled with chromatographic separation, this chemiluminescence assay can be used to examine the contribution of individual antioxidants and monitor specific changes in foods and beverages during production and storage. Epigallocatechin and epigallocatechin gallate were found to contribute over 65% of the total chemiluminescence signal (integrated peak area) for a green tea sample. In the chromatogram for a black tea, these peaks were present but less prominent, and a small cluster of peaks representing theaflavins was observed.