A novel automated direct measurement method for total antioxidant capacity using a new generation, more stable ABTS radical cation

Clin Biochem. 2004 Apr;37(4):277-85. doi: 10.1016/j.clinbiochem.2003.11.015.


Objectives: To develop a novel colorimetric and automated direct measurement method for total antioxidant capacity (TAC).

Design and methods: A new generation, more stable, colored 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid radical cation (ABTS(*+)) was employed. The ABTS(*+) is decolorized by antioxidants according to their concentrations and antioxidant capacities. This change in color is measured as a change in absorbance at 660 nm. This process is applied to an automated analyzer and the assay is calibrated with Trolox.

Results: The novel assay is linear up to 6 mmol Trolox equivalent/l, its precision values are lower than 3%, and there is no interference from hemoglobin, bilirubin, EDTA, or citrate. The method developed is significantly correlated with the Randox- total antioxidant status (TAS) assay (r = 0.897, P < 0.0001; n = 91) and with the ferric reducing ability of plasma (FRAP) assay (r = 0.863, P < 0.0001; n = 110). Serum TAC level was lower in patients with major depression (1.69 +/- 0.11 mmol Trolox equivalent/l) than in healthy subjects (1.75 +/- 0.08 mmol Trolox equivalent/l, P = 0.041).

Conclusions: This easy, stable, reliable, sensitive, inexpensive, and fully automated method described can be used to measure total antioxidant capacity.

MeSH terms

  • Antioxidants / analysis*
  • Antioxidants / metabolism
  • Automation / methods
  • Benzothiazoles
  • Depression / blood
  • Humans
  • Hydrogen Peroxide
  • Iron / metabolism
  • Kinetics
  • Sensitivity and Specificity
  • Spectrum Analysis / methods*
  • Sulfonic Acids / metabolism*


  • Antioxidants
  • Benzothiazoles
  • Sulfonic Acids
  • 2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid
  • Hydrogen Peroxide
  • Iron