Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent
TL;DR: Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds.
Abstract: Publisher Summary This chapter discusses the analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Analyses of the Folin-Ciocalteu (FC) type are convenient, simple, and require only common equipment and have produced a large body of comparable data. Under proper conditions, the assay is inclusive of monophenols and gives predictable reactions with the types of phenols found in nature. Because different phenols react to different degrees, expression of the results as a single number—such as milligrams per liter gallic acid equivalence—is necessarily arbitrary. Because the reaction is independent, quantitative, and predictable, analysis of a mixture of phenols can be recalculated in terms of any other standard. The assay measures all compounds readily oxidizable under the reaction conditions and its very inclusiveness allows certain substances to also react that are either not phenols or seldom thought of as phenols (e.g., proteins). Judicious use of the assay—with consideration of potential interferences in particular samples and prior study if necessary—can lead to very informative results. Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds .The predictable reaction of components in a mixture makes it possible to determine a single reactant by other means and to calculate its contribution to the total FC phenol content. Relative insensitivity of the FC analysis to many adsorbents and precipitants makes differential assay—before and after several different treatments—informative.
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TL;DR: It is shown that thermal processing at 115 degrees C for 25 min significantly elevated the total antioxidant activity of sweet corn by 44% and increased phytochemical content such as ferulic acid by 550% and total phenolics by 54%, although 25% vitamin C loss was observed.
Abstract: Processed fruits and vegetables have been long considered to have lower nutritional value than the fresh produce due to the loss of vitamin C during processing. Vitamin C in apples has been found to contribute <0.4% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals. This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C. Here it is shown that thermal processing at 115 degrees C for 25 min significantly elevated the total antioxidant activity of sweet corn by 44% and increased phytochemical content such as ferulic acid by 550% and total phenolics by 54%, although 25% vitamin C loss was observed. Processed sweet corn has increased antioxidant activity equivalent to 210 mg of vitamin C/100 g of corn compared to the remaining 3.2 mg of vitamin C in the sample that contributed only 1.5% of its total antioxidant activity. These findings do not support the notion that processed fruits and vegetables have lower nutritional value than fresh produce. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risk of chronic diseases.
804 citations
TL;DR: The most popular methods for determining chain-breaking antioxidant activity (AOA) of food are considered with the aim to estimate their reliability and limitations in this paper, where the main requirements imposed on these methods have been suggested.
787 citations
Cites methods from "Analysis of total phenols and other..."
...repeatability of data obtained with the Folin–Ciocalteu method, this is expected to be quite acceptable, although the problem of its standardization remains to be solved (De Beer et al., 2003; Singleton et al., 1999)....
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...The FC assay is not selective, similar to the ABTS test, it determines both polyphenols and monophenolics (Singleton et al., 1999)....
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TL;DR: Ethanol extracts of propolis from Argentina, Australia, China, Hungary and New Zealand had relatively strong antioxidant activities, and were also correlated with the total polyphenol and flavonoid contents.
776 citations
TL;DR: The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxidant capacity (TEAC), were studied using DPPH scavenging and reducing ferric ion antioxidant potential (FRAP) assays as discussed by the authors.
751 citations
Cites background from "Analysis of total phenols and other..."
...In addition, phenolic compounds, depending on the number of phenolic groups they have, respond differently to the Folin–Ciocalteu rea-gent (Singleton et al., 1999)....
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TL;DR: From this observation emerged a versatile and comprehensive approach to surface modification of a variety of solid, porous, and nanoparticulate substrates composed of metals, ceramics, and polymers.
Abstract: Polyphenolic compounds present in tea, red wine, and chocolate form thin adherent polyphenol films on substrates through spontaneous adsorption from solution. From this observation emerged a versatile and comprehensive approach to surface modification of a variety of solid, porous, and nanoparticulate substrates composed of metals, ceramics, and polymers (see picture; ROS=reactive oxygen species).
730 citations
References
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Journal Article•
TL;DR: In this paper, the use of Folin-Ciocalteu reagent rather than the FolinDenis reagent, gallic acid as a reference standard, and a more reproducible time-temperature color development period was investigated.
Abstract: Several details of the assay of total phenolic substances have been investigated and an improved procedure developed. The improvements include the use of Folin-Ciocalteu reagent rather than the Folin-Denis reagent, gallic acid as a reference standard, and a more reproducible time-temperature color development period. The values obtained are less subject to variation and interference from several nonphenols, yet are directly comparable to the "tannin" values obtained by the previously standard method.
18,629 citations
Book•
01 Jan 2006
TL;DR: In this article, the authors present official methods of analysis of AOAC International, official methods for analysis of aOAC-related project, and a set of methods for the analysis of their work.
Abstract: Official methods of analysis of AOAC International , Official methods of analysis of AOAC International , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
8,888 citations
Journal Article•
TL;DR: In this article, a 40-sample/hour procedure was adapted from the Singleton-Rossi method of analysis for total phenols in wine and other plant extracts, and compared with small-volume manual and semi-automated versions of this analysis.
Abstract: A fully automated-continuous flow 40-sample/ hour procedure was adapted from the Singleton-Rossi method of analysis for total phenols in wine and other plant extracts. It was compared with small-volume manual and semiautomated versions of this analysis. The agreement in mg of gallic acid equivalent phenol (GAE) per liter among a series of dry wines was excellent by all three procedures. The coefficients of variation in replicate analyses averaged 5.8% for the manual, 6.2% for the semi-automated and 2.2% for the automated procedure. This greater reproducibility, plus savings of about 70% in labor and up to 40% in reagents, makes the automated procedure attractive for laboratories doing enough total phenol analyses to recoup the cost of the automating equipment. For continuous flow, color development with the Folin-Ciocalteu reagent in alkaline solution must be hastened by heating compared to slower room temperature development for the manual methods. Heating of sugar-containing samples in the alkaline solution gives interference presumably from endiol formation. Examples are given of corrections which were used successfully to estimate the true phenol content of sweet wines.
3,527 citations
TL;DR: In this article, the authors summarized research into the existing methods for the quantitative determination of tyrosine and tryptophane in proteins, including the Folin-Looney method, which is based on reaction of a phosphotungstic phosphomolybdic acid in a phenol solution.
2,527 citations
TL;DR: This chapter discusses various methods of estimating protein concentration as defined by the difference in energy between the orbital of the unexcited electron and a higher energy orbital.
Abstract: Publisher Summary This chapter discusses various methods of estimating protein concentration. Absorption spectroscopy involves the absorption of a photon by an electron. Only those photons with a certain energy level can be absorbed as defined by the difference in energy between the orbital of the unexcited electron and a higher energy orbital. The peptide bond absorbs photons below 210 nm. Because of the large number of peptide bonds in a protein, this is a highly sensitive area of the protein spectrum. Although protein conformation and some absorption by tryptophan and tyrosine residues occurs in this region, less variability between proteins is observed than at 280 nm. There is a need to avoid storing buffers in plastic containers because some plastics leach plasticizers, which absorb at ultraviolet (UV) wavelengths. Detergents can also be troublesome because many absorb UV light. If the buffer or protein solution is cold, the outside of the cuvette may need to be wiped between each reading with a lint-free wiper and the readings should be made quickly after placing the cold solution into the cuvette, because atmospheric moisture may condense on the outside of the cuvette producing an erroneously high reading.
1,521 citations