Folin-Ciocalteu reagent
Encyclopedia
The Folin–Ciocalteu reagent (FCR) or Folin's phenol reagent or Folin–Denis reagent, also called the Gallic Acid
Equivalence method (GAE), is a mixture of phosphomolybdate and phosphotungstate used for the colorimetric assay
of phenolic and polyphenol
ic antioxidant
s. It works by measuring the amount of the substance being tested needed to inhibit the oxidation of the reagent.
However, this reagent does not only measure total phenols and will react with any reducing substance. The reagent therefore measures the total reducing capacity of a sample, not just the level of phenolic compounds. This reagent forms part of the Lowry protein assay
and will also react with some nitrogen-containing compounds such as hydroxylamine
and guanidine
. The reagent has also been shown to be reactive towards thiols, many vitamins, the nucleotide base guanine, the trioses glyceraldehyde and dihydroxyacetone, and some inorganic ions. Copper complexation increases the reactivity of phenols towards this reagent.
This reagent should not be confused with Folin's reagent
, which is used to detect amines and sulfur-containing compounds.
A 1951 paper entitled "Protein measurement with the Folin phenol reagent" was the most cited
paper in the 1945–1988 Science Citation Index
, with 187,652 citations
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
Equivalence method (GAE), is a mixture of phosphomolybdate and phosphotungstate used for the colorimetric assay
Assay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
of phenolic and polyphenol
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
ic antioxidant
Polyphenol antioxidant
A polyphenol antioxidant is a type of antioxidant containing a polyphenolic substructure. Numbering over 4,000 distinct species, many of these compounds have antioxidant activity in vitro but are unlikely to have antioxidant roles in vivo...
s. It works by measuring the amount of the substance being tested needed to inhibit the oxidation of the reagent.
However, this reagent does not only measure total phenols and will react with any reducing substance. The reagent therefore measures the total reducing capacity of a sample, not just the level of phenolic compounds. This reagent forms part of the Lowry protein assay
Lowry protein assay
The Lowry protein assay is a biochemical assay for determining the total level of protein in a solution. The total protein concentration is exhibited by a color change of the sample solution in proportion to protein concentration, which can then be measured using colorimetric techniques. It is...
and will also react with some nitrogen-containing compounds such as hydroxylamine
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
and guanidine
Guanidine
Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. It is used in the manufacture of plastics and explosives. It is found in urine as a normal product of protein metabolism. The molecule was first synthesized in 1861 by the oxidative degradation of an...
. The reagent has also been shown to be reactive towards thiols, many vitamins, the nucleotide base guanine, the trioses glyceraldehyde and dihydroxyacetone, and some inorganic ions. Copper complexation increases the reactivity of phenols towards this reagent.
This reagent should not be confused with Folin's reagent
Folin's reagent
Folin's reagent or sodium 1,2-naphthoquinone-4-sulfonate is a chemical reagent used to measure levels of amines and amino acids. The reagent produces a bright red color in alkaline solutions and is also fluorescent....
, which is used to detect amines and sulfur-containing compounds.
A 1951 paper entitled "Protein measurement with the Folin phenol reagent" was the most cited
Citation
Broadly, a citation is a reference to a published or unpublished source . More precisely, a citation is an abbreviated alphanumeric expression Broadly, a citation is a reference to a published or unpublished source (not always the original source). More precisely, a citation is an abbreviated...
paper in the 1945–1988 Science Citation Index
Science Citation Index
The Science Citation Index is a citation index originally produced by the Institute for Scientific Information and created by Eugene Garfield in 1960, which is now owned by Thomson Reuters. The larger version covers more than 6,500 notable and significant journals, across 150 disciplines, from ...
, with 187,652 citations
External links
- Folin-Ciocalteu's phenol reagent Fluka data sheet.