Use of a Free Radical Method to Evaluate Antioxidant Activity
TL;DR: The antiradical properties of various antioxidants were determined using the free radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH*) in its radical form as discussed by the authors.
Abstract: The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.
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TL;DR: There is a great need to standardise antioxidant testing to minimise the present chaos in the methodologies used to evaluate antioxidants.
Abstract: The activity of antioxidants in foods and biological systems is dependent on a multitude of factors, including the colloidal properties of the substrates, the conditions and stages of oxidation and the localisation of antioxidants in different phases. When testing natural antioxidants in vitro, it is therefore important to consider the system composition, the type of oxidisable substrate, the mode of accelerating oxidation, the methods to assess oxidation and how to quantify antioxidant activity. Antioxidant effectiveness is also determined by the heterogeneity and heterophasic nature of the system, the type of lipid substrate, including its physicochemical state and degree of unsaturation, the types of initiators, notably transition metals, other components and their possible interaction. For this reason there cannot be a short-cut approach to determining antioxidant activity. Each evaluation should be carried out under various conditions of oxidation, using several methods to measure different products of oxidation. Because most natural antioxidants and phytochemicals are multifunctional, a reliable antioxidant protocol requires the measurement of more than one property relevant to either foods or biological systems. Several recent studies on natural phytochemical compounds produced conflicting results because non-specific one-dimensional methods were used to evaluate antioxidant activity. There is a great need to standardise antioxidant testing to minimise the present chaos in the methodologies used to evaluate antioxidants. Several methods that are more specific should be used to obtain chemical information that can be related directly to oxidative deterioration of food and biological systems.
1,096 citations
TL;DR: In this paper, the authors described the methods used for free radical scavenging in both substrates as well as in specific cases of their application, such as superoxide radicals scavenging (O2·-), hydrogen peroxide scavenging(H2O2), hypochlorous acid scavenging, HOCl, and hydroxyl radical scavenges (HO), among them, among them are the methods that use azo-compounds to generate peroxyl radicals.
Abstract: Free radical generation is directly related with oxidation in foods and biological systems. Therefore, the search for methods to determine free radical scavenging is important. In this work are described the methods used for this purpose in both substrates as well as in specific cases of their application. The main methods comprise superoxide radicals scavenging (O2·-); hydrogen peroxide scavenging (H2O2); hypochlorous acid scavenging (HOCl); hydroxyl radical scavenging (HO.); peroxyl radical scavenging (ROO.), among them are the methods that use azo-compounds to generate peroxyl radicals, such as the ``TRAP'' method (Total Radical-Trapping Antioxidant Parameter) and the ``ORAC'' method (Oxygen-Radical Absorbance Capacity); the scavenging of radical cation 2,2-azinobis-(3-ethylbenzothiazoline-6-sulphonate) or the ABTS or the ``TEAC'' method (Trolox Equivalent Antioxidant Capacity); the scavenging of stable radical 2,2-diphenyl-1-picrylhydrazyl or DPPH . method and the scavenging of radical cation N,N-dime...
1,085 citations
Cites background or methods from "Use of a Free Radical Method to Eva..."
...This assay has been applied to hydrolyzable tannins (Lin et al., 1974; Yoshida et al., 1989), lignans (Filleur et al., 2001), polyphenolic compounds (Brand-Williams et al., 1995; Bondet et al., 1997; Yokozawa et al., 1998), phenolic acids and derivatives (Silva et al., 2000), phenolic acids in oil…...
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..., 2001), polyphenolic compounds (Brand-Williams et al., 1995; Bondet et al., 1997; Yokozawa et al., 1998), phenolic acids and derivatives (Silva et al....
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TL;DR: In this article, the total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions were analyzed, and the effect of infusion time and infusion temperature on the phenolic contents, Ferric Reducing/Antioxidant Power (FRAP) and free radical scavenging ability was tested.
1,071 citations
Cites background from "Use of a Free Radical Method to Eva..."
...Relatively stable organic radical DPPH has been widely used in the determination of antioxidant activity of single compounds as well as the different plant extracts ( Brand-Williams, Cuvelier, & Berset, 1995; Kulis ˇic ´, Radonic ´, Katalinic ´, & Milos ˇ, 2004; Yen & Duh, 1994)....
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TL;DR: In this article, a b-carotene-linoleic acid (linoleate) model system was used to evaluate the scavenging effect on the DPPH free radical and capacity to scavenge hydroxyl free radicals.
1,067 citations
TL;DR: The results show promising perspectives for the exploitation of non-traditional tropical fruit species with considerable levels of nutrients and antioxidant capacity, as well as the considerable antioxidant capacity found for acerola – Malpighia emarginata and camu-camu – Myrciaria dubia.
1,044 citations
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TL;DR: In this paper, the autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose.
Abstract: The autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose. Xanthan strongly inhibited the peroxidation of soybean oil containing tocopherols but showed no antioxidant activity on soybean oil without tocopherols in the emulsion. Xanthan did not have hydrogen donating ability but expressed Fe2+-binding activity. The Fe2+-binding activity corresponded to the pyruvate content of xanthan. Depyruvated xanthan did not inhibit effectively the autoxidation of soybean oil. The Fe2+-chelating structure of xanthan is discussed
2,919 citations
01 Jan 1990
TL;DR: The spontaneous reaction of atmospheric oxygen with organic compounds leads to a number of degradative changes that reduce the lifetime of many products of interest to the chemical industry, especially polymers, as well as causing the deterioration of lipids in foods.
Abstract: The spontaneous reaction of atmospheric oxygen with organic compounds leads to a number of degradative changes that reduce the lifetime of many products of interest to the chemical industry, especially polymers, as well as causing the deterioration of lipids in foods. The importance of oxygen in the deterioration of rubber was demonstrated over a century ago,1 and this finding led chemists to investigate the chemistry of oxidative deterioration and its inhibition.
1,059 citations
589 citations
TL;DR: This paper cites the paradoxical actions of antioxidants in processed foods and in living biological systems in the hope that these will lead the interested reader to further substantiation of the paradoxes cited.
Abstract: Scope of the Paper This paper cites the paradoxical actions of antioxidants in processed foods and in living biological systems. Essentially, it is a recognition of patterns of contradictory behavior. Limitations of space prevent detailed treatment of the paradoxes, their mechanistic basis, or citation of any more than one or two illustrative references. It is hoped that these will lead the interested reader to further substantiation of the paradoxes cited.
275 citations