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Improved and automated Trolox equivalent antioxidant capacity method using electrochemically generated ABTS radical cation

In recent years, the association between a diet rich in antioxidants and a decreased risk of cardiovascular diseases, cancer, and other diseases related to ageing is supported by considerable epidemiological evidence. Consequently, great interest has been focused on analytical methods for determination of antioxidants and assessment of antioxidant activity of food. Two types of analytical methods are currently used for this purpose: methods based on measurement of inhibition of oxidative damage of biomolecules such as lipids or DNA, and methods based on direct measurement of scavenging of stable free radicals. Scavenging methods are generally simpler than those based on inhibition, and they have gained great popularity. The most widely used scavenging method is colorimetric Trolox equivalent antioxidant capacity (TEAC) assay, which is based on scavenging of blue-green ABTS radical cation by antioxidants present in sample. In original TEAC assay ABTS radical cation is produced by metmyoglobin or peroxidase catalysed oxidation of ABTS by hydrogen peroxide. Recently, an improved TEAC assay has been introduced, which utilize ABTS radical cation generated chemically by oxidation of ABTS with persulfate prior analysis. Both assays are time-consuming, labour-intensive, and based on the use of expensive commercially available kits. In this work a novel TEAC-based method, which enables a fully automated and high-throughput determination of antioxidant capacity of food samples, is presented. Like an original TEAC assay, presented method is based on colorimetric determination of amount of ABTS radical cation scavenged by antioxidants present in sample. To overcome the drawbacks of previously proposed TEAC assays, the ABTS radical cation was generated electrochemically by anodic oxidation of ABTS diammonium salt solution. By incorporation of ABTS radical generation step, sample mixing step, and colorimetric detection step into a compact flow-injection analysis (FIA) based system an improvement of precision, repeatability and sample throughput capability with respect to original TEAC method was achieved. Good correlation between antioxidant capacity of various food samples determined by described method and results obtained with classical TEAC assay were obtained.

Antioxidant capacity; TEAC; Electrochemical generation; ABTS

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