A Critical Appraisal of Trolox Equivalent Antioxidant Capacity (TEAC) Asaay of Antioxidants

Pankaj, Sharma (2009) A Critical Appraisal of Trolox Equivalent Antioxidant Capacity (TEAC) Asaay of Antioxidants. Masters thesis, University of Mysore.

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type:	Thesis (Masters)
Additional Information:	Taking into consideration the importance of antioxidants in day to day life, it is of great interest to the general public, medical and nutritional experts, and health and food science researchers to know the antioxidant capacity and constituents in the foods. There is now convincing evidence that foods containing antioxidants may be of major importance in disease prevention. Antioxidant activity and antioxidant capacity are terms that are often used interchangeably; though they have different meanings. The antioxidant capacity gives the information about the duration while the activity describes the starting dynamics of antioxidant action. Because of the complexity of real foods, accelerated test systems are difficult to standardize, and each antioxidant test should be calibrated for each lipid or food. Accelerated oxidation conditions should be close to the storage conditions under which the food is to be protected. Ultimately, antioxidants should be evaluated on the food itself. Of various models for assaying the antioxidant capacity, the TEAC method offers several advantages over other methods and is relatively easy method. Due to its operational simplicity, the TEAC assay has been used in many research laboratories for studying antioxidant capacity, and TEAC values of many compounds and foods samples. The TEAC is an Electron Transfer (ET) based assay. It is based on scavenging of the relatively stable blue/green [2,2’-azinobis(3- 66 ethylbenzothiazoline-6-sulfonic acid)] (ABTS) radical and its conversion into a coloured product. Degrees of decolorization measured spectrophotometrically reflect the amount of radical scavenged and thereby the antioxidative activity of the test compound. ABTS•+ is soluble in both aqueous and organic solvents and is not affected by ionic strength, so can be used in multiple media to determine both hydrophilic and lipophillic antioxidant capacities of extracts and body fluids. Moreover this method is simpler and cheaper. The TEAC measures the antioxidant capacity of the parent compound plus that of reaction products. These reaction products may have a considerable contribution to the TEAC. The ABTS radical used in TEAC assays is not found in mammalian biology and thus represents a “nonphysiological” radical source. Thermodynamically, a compound can reduce ABTS•+ if it has a redox potential lower than that of ABTS (0.68V). Recent advancements in TEAC method has opened the door for numerous variants of this method which can be effectively employed for measuring the antioxidant activity of different compounds and samples efficiently. Despite recent improvements and increased use, the TEAC assay has several limitations. The ability of an antioxidant to scavenge the artificial ABTS•+ radical may not reflect the antioxidant activity due to other mechanisms effective in complex food lipids or physiologically relevant substrates, including metal chelation, and effects of antioxidant partitioning among phase of different polarities. Many phenolic compounds have low redox potentials and can thus react with ABTS•+. Also, the TEAC reaction may not be the same for sloe reactions, and it may take long time to reach an endpoint. Thus, by using an endpoint of short duration (4 or 6 min), one may be reading before the reaction is finished and result in lowered TEAC values. However, we may conclude that “quantitative evaluation of antioxidant capacity using the TEAC can be troublesome, but it can be used to provide a ranking order of antioxidants”.
Uncontrolled Keywords:	antioxidants; TEAC method; Electron Transfer assay; spectrophotometric method
Subjects:	600 Technology > 08 Food technology > 32 Antioxidants
Divisions:	Human Resource Development
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	21 Jul 2010 04:03
Last Modified:	28 Dec 2011 10:16
URI:	http://ir.cftri.res.in/id/eprint/9576

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