Current Issues in Antioxidant Measurement

Abstract

The rationale and scope of the main issues of antioxidant measurement are presented, with basic definitions and terms in antioxidant research (such as reactive species and related antioxidative defenses, oxidative stress, and antioxidant activity and capacity) in a historical background. An overview of technical problems and expectations is given in terms of interpretation of results, precision and comparability of methods, capability of simulating physical reality, and analytical performance (sensitivity, selectivity, etc.). Current analytical methods for measuring antioxidant and antiradical activity are classified from various viewpoints. Reaction kinetics and thermodynamics of current analytical methods are discussed, describing physicochemical aspects of antioxidant action and measurement. Controversies and limitations of the widely used antioxidant assays are elaborated in detail. Emerging techniques in antioxidant testing (e.g., nanotechnology, sensors, electrochemistry, chemometry, and hyphenated methods) are broadly introduced. Finally, hints for the selection of suitable assays (i.e., preferable for a specific purpose) and future prospects are given.

ABTS/PP Decolorization Assay of Antioxidant Capacity Reaction Pathways

“…3-Ethyl-2-oxo-1,3-benzothiazoline-6-sulfonate can presumably witness a hydrazindyilidene-like adduct formation pathway, whereas 3-ethyl-2-imino-1,3benzothiazoline-6-sulfonate testifies to the imine-like adduct formation pathway. (5) The extent that the coupling reaction contributes to the reaction between antioxidants and ABTS •+ (e.g., kinetics and stoichiometry) is unclear due to the lack of quantitative estimation of their formation, and sometimes this may be quite considerable.…”

“…A recently published comprehensive overview of ABTS/TEAC assays gives an overall insight into ABTS •+ radical cation-based antioxidant capacity approaches, including different methods of ABTS •+ generation, quantification strategies, and experimental design, among others, as well as a considerable TEAC value data collection obtained using the ABTS •+ chromogen [3]. It can be assuredly stated that the ABTS/PP assay measures only the antioxidant capacity, does not estimate the antioxidant reactivity or concurrent inhibition rates, and it has some shortcomings, which are out of the scope of this work and are comprehensively enlightened in the recent reviews, for instance, Cano et al [3], Schaich et al [4], or Apak [5]. This review focuses on another issue, namely, on what happens with ABTS •+ , as well as with antioxidants, as a result of their interaction.…”

Correlation between total flavonoid content and total phenolic content on antioxidant activity of ethanol extracts from three cultivars of papaya leaves

“…In simple terms, antioxidants are inhibitors or slow down unwanted oxidation reactions. Current analysis methods for measuring antioxidants and antiviral activity are organized in various perspectives (Apak, 2019). Nutritional value can be assessed from the antioxidant activity and vitamin C content contained in extracts from vegetables, fruits and various natural products (Chaiwon et al, 2013).…”

Synthesis of Steryl Hydroxycinnamates to Enhance Antioxidant Activity of Rapeseed Oil and Emulsions

“…It is well known that ABTS and DPPH are technically simple, low-cost, spectrophotometric mixed mode assays based on single electron transfer (SET), hydrogen atom transfer (HAT) and proton coupled electron transfer (PCET) mechanisms frequently applied for determination of a sample’s free radical scavenging capacity. The ABTS method is suitable to determine the AA of both hydrophilic and lipophilic antioxidants in the same sample, while DPPH radical can only be dissolved in organic media, thus this assay has higher affinity toward lipophilic than hydrophilic antioxidants [ 28 ]. For this reason, these two analytical methods were chosen to compare the antioxidant potential of phenolic acids and their steryl esters having hydrophilic and hydrophobic character, respectively.…”