Evaluation of potential interfering agents on in vitro methods for the determination of the antioxidant capacity in anthocyanin extracts

Abstract

The evaluation of the effects of sugars, metals, acids and other antioxidants on the in vitro antioxidant capacity of purified anthocyanin extract by different techniques was the purpose of this study. Three methods and the ways of expressing their results were evaluated: ABTS TEAC (capacity equivalent to Trolox, by ABTS (2,2 0 -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid))), DPPH TEAC (capacity equivalent to Trolox, by DPPH (2,2-diphenyl-1-picrylhydrazyl)), DPPH EC50 (50% reduction in the radical, by DPPH), DPPH %Sca (reduction in the scavenging capacity, by DPPH), FRAP TEAC (capacity equivalent to Trolox, by FRAP (reduction power of iron)) and FRAP EC50 (50% reduction in the radical, by FRAP). The way of expressing DPPH and FRAP results as EC50 showed the greater interfering extent, mainly when the medium contained tartaric and ascorbic acids. The most coherent method was ABTS TEAC in which only ascorbic acid interfered. Ascorbic acid was shown to interfere in all methods; thus, it must be removed prior to determining the in vitro antioxidant capacity of anthocyanins in food materials.

Prediction of total phenolics, anthocyanins and antioxidant capacity of blackberry (Rubus sp.), blueberry (Vaccinium sp.) and jaboticaba (Plinia cauliflora (Mart.) Kausel) skin using colorimetric parameters

“…Approximate vitamin C values found in the literature are 21 mg/100 g for blackberry (Kaume et al, 2012), 190 mg/100 g for blueberry (Barcia et al, 2010), and 250 mg/100 g for jaboticaba skin (Lima et al, 2011). According to Oliveira et al, (2017), ascorbic acid influences the analyses of antioxidant capacity (ABTS, DPPH and FRAP). Probably, among other factors, this was the main reason why jaboticaba skin exhibited a higher antioxidant capacity than the other fruits.…”

High-pressure recovery of anthocyanins from grape skin pomace (Vitis viniferacv. Teran) at moderate temperature

“…There are different groups of biologically active polyphenols in grape pomace, including flavonoids phenolic acids, and condensed tannins (Abbasi et al, ; de Oliveira et al, ; Ye, Sun‐Waterhouse, You, & Abbasi, ). The most common flavonoids found in grapes are anthocyanins and variations in their chemical structures implies their high reactivity during food processing, being highly sensitive to acidity (Putnik, Bursać Kovačević, & Dragović‐Uzelac, ), heat and oxidative degradation (Bursać Kovačević, Putnik, Dragović‐Uzelac, et al, ; Patras, Brunton, O'donnell, & Tiwari, ; Ricci, Parpinello, & Versari, ) therefore their extraction from plant cells is an important task closely associated to the need of preservation their biological activity.…”

Applicability of a Voltammetric Assay Based on the Electroreduction of Oxygen to Evaluate the Antioxidant Capacity of Pequi (Caryocar brasiliense Camb.) Pulp

“…Oliveira et al 4 described the ascorbic acid as an interfering agent in the evaluation of the antioxidant capacity of anthocyanins in foods. Schaich et al 39 cited the interference caused by the oxygen dissolved in the medium and the use of organic solvents (for instance, methanol in the DPPH test).…”

“…2,3 For example, the samples must undergo a pretreatment to eliminate interfering agents, such as reducing sugars and organic acids. 4 In fact, each method has its own characteristics, such as the reaction mechanism, types of oxidation substrates, reaction medium (basic, acid or neutral), compound proof of reaction and expression of results. 1 This hinders the comparison of results obtained by different authors that used different methodologies.…”