Folin phenol, spectrophotometric

Allan G. Gornall, Charles J. Bardawill, and Maxima M. David, J. Biol. Chem., 177 751-766 (1949). Determination of Serum Proteins by Means of the Biuret Reaction. Oliver H. Lowry, Nira J. Rosebrough, A. Lewis Farr, and Rose J. Randall, J. Biol. Chem., 193 265-275 (1951). Protein Measurement with the Folin Phenol Reagent. Ennis Layne, Methods EnzymoL, 3 447-454 (1957). Spectrophotometric and Tur-bidimetric Methods for Measuring Proteins. 

In this work, we compared two routinely used methods of determination of the following wine phenolic antioxidants gallic acid, (H-)-catechin, (-)-epicatechin, fraws-resveratrol, cis-resveratrol and quercetin. We used liquid chromatographic method with UV-vis detection, the conventional Folin-Ciocalteu spectrophotometric method and chemiluminometric method. The comparisons led us to the following conclusions ... 

A method that has been the standard of choice for many years is the Lowry procedure. This method uses Cn ions along with Folin-Ciocalteau reagent, a combination of phosphomolybdic and phosphotnngstic acid complexes that react with Cn. Cn is generated from Cn by readily oxidizable protein components, such as cysteine or the phenols and indoles of tyrosine and tryptophan. Although the precise chemistry of the Lowry method remains uncertain, the Cn reaction with the Folin reagent gives intensely colored products measurable spectrophotometrically. 

Procedure A 0.002 ml aliquot of the sample solution in methanol was taken and 7 ml distilled water plus 0.1 ml Folin-Ciocalteu s phenol reagent was added and after 3 min 0.2 ml of 20% Na2C03 was included. After boiling at 90 °C (exactly 5 min) samples were cooled at room temperature and were diluted with HzO to 10 ml volume. Only distilled water and reagents were used as a blank. The absorbance of total phenolics was measured at 660 nm spectrophotometrically (a Shimadzu UV 160 spectrophotometer) as per Feldman and Hanks (1968), with a sensitivity of 0.05 pig/g d.w. A standard curve was constructed with different concentrations of ferulic acid (Serva, Germany). Concentrations of ferulic acid varied from 0.33-80jig/ml (Table 1). 

For a number of years, phenolic substances were dosed by colorimetric techniques, based on redox reactions usually known as Folin Ciocalteau methods, even if a number of adjustments were developed to fit different matrix characteristics. The Folin Cioalteau reagent is a mixture of phosphomolybdic and phosphotingstic acids, with molybdenum in the 6+ oxidation state and, when the reaction takes place, it is reduced to form a complex called molybdenum blue and tungsten blue. In this complex, the mean oxidation state is between 5 and 6 and the formed complex is blue so it can be read spectrophotometrically at 750 nm. 

The concentrations of phenolic compounds were determinedby HPLC (Waters) using a method described previously by Nilvebrant et al. (21). The total concentration of phenols was also estimated by a spectrophotometric method (23) based on the Folin and Ciocalteu s reagent (Sigma). 

There are few spectrophotometric methods published to determine ezetimibe in pharmaceutical dosage forms. The first one was established by Mishra et al. [17] by applying colorimetric assay of phenol group. This method was developed based on the reaction between Folin-Ciocalteu s (FC) phenol reagent and phenol group of ezetimibe, which results in a blue chromogen that was then observed at 760 nm. 

Spectrophotometric determination of total antioxidant potential (TAPsp) was performed with oxidation of phenolic compounds with Folin-Ciocalteu reagent after... 

The spectrophotometric method commonly applied in determining the phenols in the water-methanol extract is based on the use of Folin-Ciocalteu reagent. Results are usually expressed as gallic acid equivalents (mg gallic acid/kg oil) (Rover Brown, 2013). 

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