Analytical Methods Used in Determining Antioxidant Activity: A Review

Abstract

The study of antioxidants and their implications in various fields, from food engineering to medicine and pharmacy, is of major interest to the scientific community. The present paper is a critical presentation of the most important tests used to determine the antioxidant activity, detection mechanism, applicability, advantages and disadvantages of these methods. Out of the tests based on the transfer of a hydrogen atom, the following were presented: the Oxygen Radical Absorption Capacity (ORAC) test, the Hydroxyl Radical Antioxidant Capacity (HORAC) test, the Total Peroxyl Radical Trapping Antioxidant Parameter (TRAP) test, and the Total Oxyradical Scavenging Capacity (TOSC) test. The tests based on the transfer of one electron include the Cupric Reducing Antioxidant Power (CUPRAC) test, the Ferric Reducing Antioxidant Power (FRAP) test, the Folin–Ciocalteu test. Mixed tests, including the transfer of both a hydrogen atom and an electron, include the 2,2′-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) test, and the [2,2-di(4-tert-octylphenyl)-1 -picrylhydrazyl] (DPPH) test. All these assays are based on chemical reactions and assessing the kinetics or reaching the equilibrium state relies on spectrophotometry, presupposing the occurrence of characteristic colours or the discolouration of the solutions to be analysed, which are processes monitored by specific wavelength adsorption. These assays were successfully applied in antioxidant analysis or the determination of the antioxidant capacity of complex samples. As a complementary method in such studies, one may use methods based on electrochemical (bio)sensors, requiring stages of calibration and validation. The use of chemical methods together with electrochemical methods may result in clarification of the operating mechanisms and kinetics of the processes involving several antioxidants.

Microalgae as Sustainable Bio-Factories of Healthy Lipids: Evaluating Fatty Acid Content and Antioxidant Activity

“…The ABTS ●+ and DPPH ● radical scavenging assays were used to assess this biological potential of lipid extracts from seven different microalgae. For the evaluation of the antioxidant potential, it is useful to use distinct methods as distinct compounds and different mechanisms may underly the antioxidant potential [ 107 , 108 ]. Among the different methods for antioxidant activity screening, the DPPH and ABTS assays are the most used ones due to their methodological simplicity and stability of the radicals.…”

“…Among the different methods for antioxidant activity screening, the DPPH and ABTS assays are the most used ones due to their methodological simplicity and stability of the radicals. The ABTS assay evaluates the capacity of the extracts to reduce the ABTS ●+ radical, which is generated previously through the oxidation of the ABTS, while the DPPH assay evaluates the capacity of the extracts to reduce the DPPH ● radical, which is a stabilized radical by itself [ 108 , 109 ]. Both assays were used to evaluate the antioxidant properties of the microalgae lipid extracts, with T. chui showing the highest IC20 in the DPPH assay.…”

Antiradical Properties of N-Oxide Surfactants—Two in One

“…This approach is based on the logical assumption that if a compound can react with the stable radical, it is certainly capable of reacting with much more aggressive radicals, such as •OH. The amount of stable radical reduced/remaining in the sample depends on the power (kind) of the antiradical compound (antioxidant) [ 7 , 21 ].…”

“…From Figure 3 , we can see that both di- and mono-N-oxides scavenge DPPH• more actively, and therefore DPPH• was used in our further studies as it seems to better mimic more reactive radicals such as •OH. Moreover, DPPH• is reliably used in similar studies [ 8 , 21 , 28 ].…”

Proteome Analysis and In Vitro Antiviral, Anticancer and Antioxidant Capacities of the Aqueous Extracts of Lentinula edodes and Pleurotus ostreatus Edible Mushrooms

“…While the phosphomolybdate assay is commonly used to express the total antioxidant capacity (TAC), all three methods used in this manuscript have been reported to evaluate the TAC. Munteanu and Apetrei (2021), in their review on the methods used in determining antioxidant activity, described the ABTS radical scavenging assay as a “simple and convenient method used to measure the total antioxidant capacity (TAC)” [ 83 ]. In their comparative study, Csepregi et al (2016) compared four methods used for evaluation of the TAC, which were Trolox equivalent antioxidant capacity (TEAC), the ferric reducing antioxidant potential (FRAP), the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and Folin–Ciocalteu reagent reactivity (FCR) [ 84 ].…”