Reagent, Folin-Ciocalteu

SINGLETON v L, ORTHOFER R and LAMUELA-RAVENTOS R M (1999) Analysis of total phenolics and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent, Meth Enzymol, 299, 152-78. 

Singleton, V. L., Orthofer, R., and Lamuela-Raventos, R. M. (1999). Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. In "Methods in Enzymology, Oxidant and Antioxidants (Part A)", (L. Packer, Ed.), vol. 299 pp. 152-178. Academic Press, San Diego, CA. 

The Folin-Ciocalteu assay is the most widely used method to determine the total content of food phenolics (Fleck and others 2008). Folin-Ciocalteu reagent is not specific and detects all phenolic groups found in extracts, including those found in extractable proteins. A disadvantage of this assay is the interference of reducing substances, such as ascorbic acid (Singleton and others 1999). The content of phenolics is expressed as gallic acid or catechin equivalents. 

Total Phenols Assay (Folin-Ciocalteu Reagent)... 

Clarke has reported that diloxanide furoate gives a blue color with the Folin-Ciocalteu Reagent, and also yields a yellow color when subjected to Libermann s test [7],... 

Diloxanide furoate was determined by Sane al. using a simple spectrophotometric method [28]. The drug was extracted from tablets with ethanol, or was filtered from a suspension and dissolved in ethanol. The resulting solution was mixed with 6% aqueous sodium hydroxide and Folin-Ciocalteu reagent, or with a 1% solution of sodium nitroprusside in aqueous 10% sodium hydroxide. The complexes formed had absorbance maxima at 650 run, or at 675 nm, respectively. 

In vitro tests, used in evaluation of antioxidant properties make use of the ability of antioxidants to quench free radicals. Based on this mechanism, the methods are divided into two groups SET - single electron transfer, and HAT - hydrogen atom transfer. Reactions with antioxidants in assays with the DPPH radical, ABTS and the Folin-Ciocalteu reagent both operate according to the SET and HAT mechanism. Due to the kinetics of the reaction, they are included in the... 

Performing the assay is reduced to putting an alcoholic solution of the analysed sample, Folin-Ciocalteu reagent and solution of sodium carbonate into a reaction tube, which brings the pH of the reaction environment to approx. 10. According to various literature reports, the reaction runs in the darkness for 10 to 120 minutes. After that time, the blue colour of the solution is observed colorimetrically at 725 nm - 760 nm [34, 35, 36, 37, 38]. The results are expressed based on calibration curves prepared for catechol and gallic acid. 

At the end of the first tube s 10-min incubation, add 100 il freshly diluted 1 N Folin-Ciocalteu reagent (freshly diluted from a 2 N stock). Immediately vortex the tube for 2 to 3 sec. Continue to maintain the 15-sec intervals from step 3 for addition of the reagent to the remaining tubes. 

Using a multichannel pipettor, quickly add 20 pi freshly diluted 1 N Folin-Ciocalteu reagent to each well. Immediately mix on a plate mixer for 30 sec. 

Total phenolic content the Folin-Ciocalteu reagent... 

Scalbert et al. (1989) used a slight modification of this method, whereby a 2.5 mL aliquot of the Folin-Ciocalteu reagent (diluted 10 times in water) and 2 mL of a 75g/L solution of sodium carbonate are added to 0.5 mL of the extract (diluted in methanol), followed by a 5 min. incubation in a 50°C waterbath. A potential complication of this method is the deglycosylation of phenolic compounds due to the heating. 

A third method relies on the precipitation of proanthocyanidins with formaldehyde. First, the total phenolic content is measured using the Folin-Ciocalteu reagent as described before. A 0.5 mole equivalent of phloroglucinol (1.3) is added for every gallic acid equivalent in the extract. To 2 mL of this plant extract and phloroglucinol is added 1 mL of a 2 5 HC1 /H20 solution and 1 mL of an aqueous solution of formaldehyde (13 mL of 37% formaldehyde diluted to 100 mL in water). After an overnight incubation at room temperature, the unprecipitated phenols are estimated in the supematent by the Folin-Ciocalteu method. The precipitate contains the proanthocyanidins and the known amount of phloroglucinol, which is always quantitatively precipitated. 

Method D Sample was reacted with Folin-Ciocalteu reagent and the absorbance was measured at 770 nm. 

This method was adapted as follows for use with the Spekker micro-cells. The volume of each component of the incubation mixture was reduced to0.1 ml. after incubation for 1 hr., 0.5 ml. of Folin-Ciocalteu reagent, diluted as above, was added. Protein was sedimented, and 0.5 ml. of the supernatant liquor was mixed with 0.5 ml. of 1.33 N sodium carbonate solution. The color was developed as before. 

Sastry and Rao [24] reported the determination of mefenamic acid and some NSAIDs in pharmaceuticals by a spectrophotometric method. The method is based on the formation of a blue complex with Folin-Ciocalteu reagent, and subsequent measurement of the absorbance at 750-760 nm. The method was found to be simple, sensitive, accurate, and rapid, with recoveries of 98.0-102.3% and relative standard deviations of 1.04-1.66%. 

Folin-Ciocalteu (Lowry) Assay. The quantitative Folin-Ciocalteu assay (also often called the Lowry assay ) can be applied to dried material as well as to solutions. In addition, the method is sensitive samples containing as little as 5 /Ug of protein can be analyzed readily. The color formed by the Folin-Ciocalteu reagent is thought to be caused by the reaction of protein with the alkaline copper in the reagent (as in the biuret test) and the reduction... 

Strong Acid Fraction Aromaticity Ferric Chloride Folin-Ciocalteu Reagent Liebermann s Test Millon s Reagent Nessler s Reagent... 

Indications. A red or orange-red colour indicates the presence of a phenolic substance. Primary aryl amines also react. Some basic compounds which contain a phenolic group do not react to this test a combination of this test with the Folin-Ciocalteu Reagent is therefore advised for phenolic compounds. 

Colour Tests. Ammoniacal Silver Nitrate—red-brown/red-brown Ferric Chloride—green Folin-Ciocalteu Reagent— blue Marquis Test—orange—> violet Methanolic Potassium Hydroxide—pink-orange—> brown Nessler s Reagent—black Palladium Chloride—orange —> brown Potassium Dichromate (Method 1)—green— brown. 

Colour Test. Folin-Ciocalteu Reagent—grey-blue. 

Colour Tests. Ferric Chloride—brown Folin-Ciocalteu Reagent—blue Liebermann s Test—black Millon s Reagent— pink— red. 

Colour Tests. Coniferyl Alcohol—orange Ferric Chloride— violet Folin-Ciocalteu Reagent—blue McNally s Test—brown precipitate. 

Colour Tests. Folin-Ciocalteu Reagent—blue Liebermann s Test—violet-brown Mandolin s Test—blue - green. 

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