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Book ChapterDOI

Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent

01 Jan 1999-Methods in Enzymology (Academic Press)-Vol. 299, pp 152-178
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.
Citations
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Journal ArticleDOI
TL;DR: This analysis suggests that the total phenols assay by FCR be used to quantify an antioxidant's reducing capacity and the ORAC assay to quantify peroxyl radical scavenging capacity, to comprehensively study different aspects of antioxidants.
Abstract: This review summarizes the multifaceted aspects of antioxidants and the basic kinetic models of inhibited autoxidation and analyzes the chemical principles of antioxidant capacity assays. Depending upon the reactions involved, these assays can roughly be classified into two types: assays based on hydrogen atom transfer (HAT) reactions and assays based on electron transfer (ET). The majority of HAT-based assays apply a competitive reaction scheme, in which antioxidant and substrate compete for thermally generated peroxyl radicals through the decomposition of azo compounds. These assays include inhibition of induced low-density lipoprotein autoxidation, oxygen radical absorbance capacity (ORAC), total radical trapping antioxidant parameter (TRAP), and crocin bleaching assays. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes color when reduced. The degree of color change is correlated with the sample's antioxidant concentrations. ET-based assays include th...

5,354 citations

Journal ArticleDOI
TL;DR: The anticancer effects of phenolics in-vitro and in- vivo animal models are viewed, including recent human intervention studies, and possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.
Abstract: Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

3,213 citations


Cites background or methods from "Analysis of total phenols and other..."

  • ...Because of the heterogeneity of natural phenolics and the possible interference from other readily oxidized substances in the plant materials, it is not surprising that several methods have been used for determination of total phenolics and none are perfect [90]....

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  • ...C reagent is added ahead of alkali [90]....

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  • ...The F-C assay relies on the transfer of electrons in alkaline medium from phenolic compounds to phosphomolybdic/phosphotungstic acid complexes to form blue complexes (possibly (PMoW11O40)) that are determined spectroscopically at approximately 760 nm [90,91]....

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  • ...In most cases, F-C has been found preferable as compared to the other methods [90]....

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  • ...Sulfites and sulfur dioxide which is a common additive for wine can cause enhancing effect [90]....

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Journal ArticleDOI
TL;DR: Thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce.
Abstract: Processed fruits and vegetables have been long considered to have lower nutritional value than their fresh commodities due to the loss of vitamin C during processing This research group found vitamin C in apples contributed < 04% 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 elevated total antioxidant activity and bioaccessible lycopene content in tomatoes and produced no significant changes in the total phenolics and total flavonoids content, although loss of vitamin C was observed The raw tomato had 076 +/- 003 micromol of vitamin C/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the vitamin C content significantly dropped to 068 +/- 002, 064 +/- 001, and 054 +/- 002 micromol of vitamin C/g of tomato, respectively (p < 001) The raw tomato had 201 +/- 004 mg of trans-lycopene/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the trans-lycopene content had increased to 311+/- 004, 545 +/- 002, and 532 +/- 005 mg of trans-lycopene/g of tomato (p < 001) The antioxidant activity of raw tomatoes was 413 +/- 036 micromol of vitamin C equiv/g of tomato With heat treatment at 88 degrees C for 2, 15, and 30 min, the total antioxidant activity significantly increased to 529 +/- 026, 553 +/- 024, and 670 +/- 025 micromol of vitamin C equiv/g of tomato, respectively (p < 001) There were no significant changes in either total phenolics or total flavonoids These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against 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 risks of chronic diseases

2,738 citations

Journal ArticleDOI
TL;DR: A microplate-adapted colorimetric total phenolics assay that utilizes Folin–Ciocalteu (F–C) reagent is described that eliminates approximately 85% of ascorbic acid and other potentially interfering compounds.
Abstract: Non-structural phenolic compounds perform a variety of functions in plants, including acting as antioxidants. We describe a microplate-adapted colorimetric total phenolics assay that utilizes Folin-Ciocalteu (F-C) reagent. The F-C assay relies on the transfer of electrons in alkaline medium from phenolic compounds to phosphomolybdic/phosphotungstic acid complexes, which are determined spectroscopically at 765 nm. Although the electron transfer reaction is not specific for phenolic compounds, the extraction procedure eliminates approximately 85% of ascorbic acid and other potentially interfering compounds. This assay is performed in microcentrifuge tubes and assessed in a 96-well plate reader. At least 64 samples can be processed in 1 d.

2,047 citations


Cites background from "Analysis of total phenols and other..."

  • ...The F–C assay relies on the transfer of electrons in alkaline medium from phenolic compounds to phosphomolybdic/phosphotungstic acid complexes to form blue complexes that are determined spectroscopically at approximately 760 n...

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Journal ArticleDOI
TL;DR: In this paper, several honey samples (27) from Burkina Faso were analyzed to determine their total phenolic, flavonoid and proline contents as well as their radical scavenging activity.

1,850 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

Journal ArticleDOI
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

Book ChapterDOI
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