Trolox equivalents antioxidant capacity

Gliszczyhska-Swigl, A. (2006). Antioxidant activity of water soluble vitamins in the TEAC (trolox equivalent antioxidant capacity) and the FRAP (ferric reducing antioxidant power) assays. Food Chemistry, Vol.96, No.l, (May 2006), pp. 131-136, ISSN 0308-8146. 

Radical Cation 2,2-Azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS 1) TEAC Assay (Trolox Equivalent Antioxidant Capacity) or ABTS Assay... 

The Trolox equivalent antioxidant capacity (TEAC) assay was reported first by Miller and others (1993) and Rice-Evans and Miller (1994). They used the peroxidase activity of metmyoglobin to oxidize 2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in the presence of hydrogen peroxide. The TEAC assay is based on the... 

In vitro Antioxidant capacity was measured by the method of Trolox equivalent antioxidative capacity (TEAC) [12]. The TEAC assay used 20 pL of the extract sample mixed with a 980 pL solution of ABTS + [2.2 -azobis-(3-ethylenebenzothia-zohne-6-srrlfonic) acid], the decolorization of ABTS ", which is a long-life radical cation and bine-green chromophore, measrrred at 734 nm. Results are expressed as millimoles of Trolox equivalent per kilograms of fresh weight. 

Trolox Equivalent Antioxidant Capacity (TEAC) assay... 

TRAP, Total peroxyl-radical-trapping antioxidant capability of plasma TEAC, Trolox equivalent antioxidant capacity FRAP, ferric-reducing activity of plasma ORAC, oxygen-radical-absorbing capacity PCA, perchloric acid-soluble fraction ABAP, 2,2 -azobis(2-amidoproane). 

Correlate the decrease observed in a dose-response curve with a standard antioxidant (e.g., trolox, ascorbic acid), expressing the antioxidant activity as equivalents of standard antioxidant, a well-established parameter in this respect being Trolox Equivalent Antioxidant Capacity (TEAC). ... 

Trolox (2,5,7,8-tetramethyl-2-carboxy-6-hydroxychroman) . This test is referred to as the TEAC or Trolox-Equivalent Antioxidant Capacity assay. 

Flavonoids as antioxidants have been reviewed several times 45s including an outline of many claims to their beneficial health effects . Due to their complex structures and different classes (eight thousand different compounds are known ), researchers often resorted to qualitative screening methods to evaluate their antioxidant potentials in mixed aqueous/lipid phases. For example, the so-called Trolox equivalent antioxidant capacity (TEAC), the concentration of Trolox with equivalent antioxidant activity of a 1 mM concentration of the substrate, is frequently used in heterogeneous systems. Unfortunately, this can be an unreliable measure of the activity of the substance, especially if initiation is also carried out in the aqueous phase. Nevertheless, there have been some efforts made to evaluate antioxidant activities of specific flavonoids using more quantitative methods in heterogeneous systems in order to mimic natural environments. A few examples are cited below to illustrate some approaches to determine flavonoid activities in micelles or lipid membranes. 

The xanthone compounds l,3,5-trihydroxy-2-(2, 2 -dimethyl-4 -isopropenyl) cyclopentanylxanthone, 5-0-demethyl-6-deoxypaxanthonin, and 5-0-de-methylpaxanthonin, as well as 3,5-dihydroxybenzophenone-4-/8-D-glucoside and 3-geranyl- l-(3-methylbutanoyl)phloroglucinol isolated from the leaves of Hypericum styphelioides, were evaluated for their antioxidative properties in Trolox equivalent antioxidant capacity (TEAC) and chemiluminescence (CL) assays. 

A sensitive and simple chemiluminescent (CL) method for measuring antioxidant activity was developed. The determination of TEAC (Trolox equivalent antioxidant capacity) is based on the inhibition of CL intensity of luminol by an antioxidant. Antimicrobial activity was tested as a minimal inhibitory concentration (MIC) by broth microdilution method on gram-positive Enterococcus faecalis. Staphylococcus aureus) and gram-negative Pseudomonas aeruginosa, Escherichia coli) bacterial strains. 

The graph (Fig. 1) shows the dependence of TEAC (Trolox Equivalent Antioxidant Capacity) on the different types of tea. The tea solutions were neither made fresh - the white column - nor frozen for one year - the grey column. 

IC50 is the concentration required for 50% inhibition of lipid peroxidation or scavenging of DPPH radical. TEAC is the trolox equivalent antioxidant capacity, which is defined as the mM concentration of a trolox solution having the antioxidant capacity equivalent to a 1.0 mM solution of the substance under investigation. 

Siriwardhana and Shahidi [33] evaluated the Trolox equivalents antioxidant capacity (TEAC) of almond and its by-product extracts and found that ethanolic extracts, at the same concentration the TEAC values, followed the order of brown skin > green shell cover > whole seed (kernel). Values of brown skin and green shell cover extracts were 12.6- and 9.8-fold higher than that of whole seed extract, respectively. Alasalvar et al. [30] observed that hazelnut kernel and its green leafy cover extracts from 80% (v/v) ethanol were characterized as having significantly lower (P < 0.05) total antioxidant activity compared to those of extracts obtained from 80% (v/v) acetone. 

From Frankel and Meyer (2000). TEAC, Trolox equivalent antioxidant capacity ORAC, oxygen radical absorbance capacity GA, gallic acid. 

Comparison of the pKa values to the pH-dependent antioxidant profiles, determined by the Trolox equivalent antioxidant capacity, revealed that for various hydroxyflavones the pH-dependent behaviour is related to hydroxyl moiety deprotonation, resulting in an increase of the antioxidant potential upon formation of the deprotonated form (Lemai ska et al. 2001). 

---