title: In vitro measurements and interpretation of total antioxidant capacity.
abstract: BACKGROUND
  One of the strategies most commonly used to assess a free radical-antioxidant balance in chemical and biological systems is the determination of the total antioxidant capacity (TAC). A large amount of research has been published using TAC. However, it remains unclear which is the significance of these investigations for understanding the biological importance of free radical reactions.
  
  
  METHODS
  This review discusses the relevance and limitations of TAC for the assessment of the antioxidant activities present in food and food derivatives, and in body tissues and fluids.
  
  
  CONCLUSIONS
  TAC determinations are simple, inexpensive, and able to evaluate the capacity of known and unknown antioxidants and their additive, synergistic and/or antagonistic actions, in chemical and biological systems. However, different TAC assays correlate poorly with each other, since each TAC assay is sensitive to a particular combination of compounds, but exclude many others. The TAC values for foods cannot be translated to the in vivo (human) antioxidant defenses, and furthermore, to health effects provided by that food.
  
  
  CONCLUSIONS
  Up to date, conclusions that can be drawn from the extensive amount of research done using TAC of foods or populations should not be considered when used for making decisions affecting population health. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.
authors.affiliation: Physical Chemistry, School of Pharmacy and Biochemistry, University of Buenos Aires - Institute of Molecular Biochemistry and Medicine (IBIMOL), National Council of Scientific and Technological Research (CONICET), Buenos Aires, Argentina; Department of Nutrition, University of California at Davis, Davis, CA 95616, USA. Electronic address: cfraga@ffyb.uba.ar.
authors.forename: Cesar G
authors.initials: CG
authors.lastname: Fraga
authors.forename: Patricia I
authors.initials: PI
authors.lastname: Oteiza
authors.forename: Monica
authors.initials: M
authors.lastname: Galleano
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis* / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species
keywords: Antioxidant; FRAP; ORAC; Oxidant; Radical scavenging; TEAC