Journal ArticleDOI
Use of a Free Radical Method to Evaluate Antioxidant Activity
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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.read more
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Journal ArticleDOI
Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing
María I. Gil,Francisco A. Tomás-Barberán,Betty Hess-Pierce,Deirdre M. Holcroft,Adel A. Kader +4 more
TL;DR: HPLC-DAD and HPLC-MS analyses of the juices revealed that commercial juices contained the pomegranate tannin punicalagin while only traces of this compound were detected in the experimental juice obtained from arils in the laboratory, which shows that pomesgranate industrial processing extracts some of the hydrolyzable tannins present in the fruit rind.
Journal ArticleDOI
Screening of Brazilian plant extracts for antioxidant activity by the use of DPPH free radical method
Luciana Lopes Mensor,Fábio de Sousa Menezes,Gilda Guimarães Leitão,Alexandre da Silva Reis,Tereza Cristina dos Santos,Cintia S. Coube,Suzana G. Leitão +6 more
TL;DR: As a general rule the ethanol extracts of plants belonging to the Verbenaceae family showed lower EC50 values than the other plant extracts, among the partitions, the more polar ones (ethyl acetate and n‐butanol) are those that generally have higher antioxidant activity (AA).
Journal ArticleDOI
Antioxidant activity of dietary polyphenols as determined by a modified ferric reducing/antioxidant power assay
TL;DR: The antioxidant (AO) activity of polyphenols (PPs) was determined for the first time using a modified FRAP (ferric reducing/antioxidant power) assay and polyphenol's AO efficiency seemed to depend on the extent of hydroxylation and conjugation.
Journal ArticleDOI
Screening of Plant Extracts for Antioxidant Activity: a Comparative Study on Three Testing Methods
TL;DR: Three methods widely employed in the evaluation of antioxidant activity, namely 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, static headspace gas chromatography (HS-GC) and beta-carotene bleaching test (BCBT), have been compared with regard to their application in the screening of plant extracts.
Journal ArticleDOI
Screening of radical scavenging activity of some medicinal and aromatic plant extracts
TL;DR: In this paper, 12 medicinal and aromatic plants were investigated for their radical scavenging activity using DPPH and ABTS assays: Salvia sclarea, Salvia glutinosa, Salmine pratensis, Lavandula angustifolia, Calendula officinalis, Matricaria recutita, Echinacea purpurea, Rhaponticum carthamoides, Juglans regia, Melilotus officinalIS, Geranium macrorrhizum and Potentilla fruticosa.
References
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Journal ArticleDOI
Antioxidative properties of xanthan on the autoxidation of soybean oil in cyclodextrin emulsion
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.
Book ChapterDOI
The Mechanism of Antioxidant Action in Vitro
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.
Journal ArticleDOI
Comparison of the Antioxidative Activity of Some Acid-phenols: Structure-Activity Relationship
Journal ArticleDOI
Paradoxical behavior of antioxidants in food and biological systems.
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.