Evaluation of the antioxidant activity by flow injection analysis method with electrochemically generated ABTS radical cation

Abstract

A Trolox equivalent antioxidant capacity (TEAC) decolourisation assay was adapted to a flow injection analysis (FIA) system and a simple and rapid method for antioxidant activity evaluation was developed. To avoid the time consuming step of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical cation preparation by chemical oxidation of ABTS, as in the original TAEC assay, and hence, to shorten the analysis time, the ABTS radical cation was generated on-line by electrochemical oxidation of ABTS in the flow-through electrolysis cell forming a part of the FIA system. The proposed method was optimised with respect to a flow rate, injection volume and ABTS radical cation/carrier ratio. Under the optimised conditions linear calibration graphs for Trolox were obtained over the range 10-100 microM, with a limit of detection 1.6 microM. Good reproducibility (relative standard deviation 1.95%) and sample throughput (32 samples per hour) were achieved. The developed method was applied to the evaluation of the antioxidant activity of pure compounds and samples of some common beverages. In both cases a good correlation between the results obtained by the proposed method and TEAC values evaluated by the classic TAEC decolourisation assay was obtained (r(2)= 0.996 for pure compounds and r(2)= 0.957 for beverage samples).

Green tea preparation and its influence on the content of bioactive compounds

“…Determination of antioxidant capacity of tea infusions was conducted by Flow Injection Analysis (FIA) with electrochemically generated ABTS radical cation (Iveković , Milardović , Roboz, & Grabarić , 2005). This method is based on the scavenging of stable blue-green ABTS radical cation (ABTS *+ ), formed either by chemical (Re et al, 1999;Van der Berg, Haenen, Van der Berg, & Bast, 1999) or enzymatic (Arnao, Cano, & Acosta, 2001;Lemanska et al, 2001) oxidation of ABTS several hours prior to the analysis.…”

“…In order to avoid the time consuming step of ABTS radical cation preparation, FIA modification of TEAC method was employed. FIA is based on the electrochemical production of ABTS radical cation in the electrolysis flow-cell forming the part of FIA system (Iveković et al, 2005). A 0.1 mol/L phosphate buffer solution (pH = 7.40) was used as a carrier stream, and the solution of ABTS radical cation generated electrochemically was employed as a second (reagent) stream.…”

Characterisation of Pinotage Wine During Maturation on Different Oak Products

“…Ellagitannins, which were not measured in the present study, are also likely to contribute to the increased TAC R during oak maturation due to their extraction from the oak wood. Ellagitannins have been shown to have high radical scavenging activity (Saint-Cricq de Gaulejac et al, 1998), while the hydrolysis products of ellagitannins, namely ellagic acid (Ivekovic et al, 2005) and gallic acid (Jordão et al, 2005), are also potent antioxidants due to the many available hydroxyl groups. Ellagic tannins are extracted rapidly into a hydro-alcoholic medium, such as wine, followed by a gradual decrease (Jordão et al, 2005).…”

Biological Properties of Acidic Cosmetic Water from Seawater

“…Therefore, PBMC was often used in immune regulation tests, and several cell-type-specific activation cytokines in PBMCs were identified [23]. More specifically, we selected TNF-α and IL-4 as monocytes/macrophage triggering cytokines.…”

“…The ABTS radical-scavenging assay was conducted according to the trolox equivalent antioxidant capacity (TEAC) Assay of Damir Iveković [23]. Briefly, each sample solution (0.08 mL) was mixed with 4.92 mL of the ABTS solution (7 mM final concentration in 5 mM phosphate buffer (pH 7.4)).…”