Folin-Ciocalteau method

The express method of phenolic compounds determination was designed. It is based on heterogeneous azo-coupling reaction of phenols, which different extracts of fresh raw material contain, with aryldiazonium salts grafted on the silica surface. We can carry out phenols analysis on-site, as formation of immobilized azocompounds leads to a drastic change in the sorbent s color. Thus, we pui pose a new method, that allows to indicate herb phenols in aqueous and non-aqueous medias and to compare it with a well-known Folin-Ciocalteau method. 

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. 

Chlorpromazine can cause falsely increased CSF protein (Folin-Ciocalteau method) (26). 

Antioxidant Activity towards Human LDL. At equivalent total phenol levels (by the Folin Ciocalteau method), all samples had similar activity at 10.0 pM where inhibition was generally above 95%. At 20 pM GAE all wines inhibited more than 99% of LDL oxidation regardless of the fining agent used. However, the wines had very different antioxidant activities at 5.0 pM (Table IV). The antioxidant activity at 5.0 pM GAE increased with all fining agents and dramatically with PVPP and bentonite. Because the antioxidant activities were compared after dilutions to equivalent total phenol levels, it is important to note that the data shows which samples of phenolics have the most potency at the same concentration, not which sample has the highest antioxidant concentration. 

In a study of 92 Finnish edible and nonedible plant materials, a total of 15 berry samples were screened for antioxidant activity (Kahkonen et al., 1999). The activity was compared with the total phenolic content of the samples. Inhibition of methyl linoleate oxidation was used as a measure of antioxidant activity of berry acetone extracts and total phenolics determined by the Folin-Ciocalteau method as GAE/g dry matter of extracts. Berry extracts were high in antioxidant activity among the... 

Total antioxidant activities in 13 typical Italian wines were determined with an average of 12.3 pM Trolox equivalents for red wines and 1.6 pM for white wines (Simonetti et al., 1997). The values correlated well with total phenols (r = 0.9902) and flavanols (r = 0.9270) and clearly demonstrated that red wine polyphenols are significant in vitro antioxidants. The antioxidant capacity of 16 red wines from several countries was tested using electron spin resonance (ESR) spectroscopy (Bums et al., 2000). The antioxidant activity ranged from 4.13 x 1021 to 9.29 x 1021 number of Fremy s radicals reduced by 1 L of wine. The antioxidant capacity was associated with the phenolic content of the wines, determined either by Folin-Ciocalteau or by summation of the individual phenolics determined by HPLC or by spectroscopy. Total phenolics as measured by the Folin-Ciocalteau method ranged from 6.47 to 18.6 mM GAE per liter. The anthocyanin levels ranged from 101.5 to 325.7 pM. There were substantial differences in the proportion of polymeric pigments in the wines. 

Diagrams show that diy and semi-dry red wines have the highest values of the total phenol AO content (from 200 to 430 mg/1 GA), that is essential more than dry and semi-diy white wines (from 50 to 200 mg/1 GA). The phenolic content of red semisweet wines also dominate compared with semi-sweet white wines and champagnes. In work [10] the total content of phenols has been measured in dry red wines by the Folin-Ciocalteau method with GA as a standard. Values of the phenol content have appeared in 2-5 times more, than in the present work. Apparently, it is possible to explain that besides phenols, with a reactant of Folin-Ciocalteau can react other substances... 

The most commonly used methods for determination of total phenolics in foodstuffs are the Prussian Blue assay and the Folin-Ciocalteau method. Although these procedures have undergone numerous modiiicalions, the version adopted by the American Oil Chemists Society (AOCS) is most commonly used nowadays. These assays are not specific for phenohc compounds, although they are widely used to get a global concentration of phenolic compounds present in foods. 

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