Folin Ciocalteu’s phenol reagent

Materials required Sample solution in methanol, distilled water, 20% Na2C03, Folin-Ciocalteu s phenol reagent, water bath, graduated tube, cuvette, micro pipette (0.1 ml), pipette of 1,2 and 10 ml, test tubes of 20 ml, pure ferulic acid (Serva, Germany), Shimadzu UV 160 spectrophotometer. 

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). 

G Mix just before use Soln. C, D, E, and F in a ratio of 1 1 28 10 H Folin-Ciocalteu s phenol reagent (stock), diluted 1+3 with ddH20... 

Fumed silica A-200 (Pilot plant at the Institute of Surface Chemistry, Kalush, Ukraine specific surface area Ascorbic acid (vitamin C) and all-rac-a-Tocopheryl acetate (vitamin E acetate) were used as adsorbates. Folin-Ciocalteu s phenol reagent (Merck) was used to measure the total polyphenolic index. Silica samples with different degree of surface silylation were obtained using gas-phase chemical modification of highly disperse silica (A-200) surface by trimethylchlorosilane.6... 

Antioxidant activity of silica nanocomposites with immobilized vitamin C was tested using the polyphenolic activity index.8 After adsorption of ascorbic acid on the silica surface and centrifugation, the excess solution was removed to obtain the suspension of a fixed volume (2 ml). Distilled water, sodium carbonate solution, and Folin-Ciocalteu s phenol reagent were subsequently added to suspensions and to the reference Vitamin C solution. The suspensions were then stored for 30 min, and the optical density of supernatant was measured at X = 750 nm. The reference solution of ascorbic acid was used to compare antioxidant activity of vitamin-containing nanocomposites with the activity of dissolved vitamin C. 

There is, however, a caveat for estimating available total phenolic acid concentrations. The estimates of the total available fraction of phenolic acids in soil extracts represent a crude estimate of what actually occurs in soil, not only because of the range of efficiencies of extraction procedures but also because different phenolic acids at the same concentration generate different absorbances with Folin Ciocalteu s phenol reagent (Fig. 3.7 Blum et al. 1991). In addition soil extracts also contain compounds, other than phenolic acids, that react with (i.e., reduce) the Folin Ciocalteu s phenol reagent (McAllister 1969 Box 1983). The assumption, therefore, was that available total phenolic acid values based on the Folin Ciocalteu s phenol reagent expressed as ferulic acid equivalence were relative values that were consistently related to the acmal total available phenolic acids (hereafter just called total phenolic acid) present in soil extracts. The extraction and quantification by HPLC analysis of available individual phenolic acids in soil do not have these particular problems. 

So what were the concentrations of phenolic acids in the Cecil A soil wheat stubble (Triticum aestivum L. Coker 916 )/soybean (Glycine maxL. Deltapine417 ) systems Subsamples taken from wheat stubble/soybean (no-till), wheat stubble tilled under/soybean (conventional-till), and fallow/soybean soil (conventional-till) cores were extracted by the water-autoclave procedure and analyzed for 7 common phenolic acids (ferulic, caffeic, p-coumaric, p-hydroxybenzoic, sinapic, syringinc, and vanillic) and total phenolic acid (Blum et al. 1991). With minor exception, individual phenolic acids were correlated with each other, with the sum of the 7 phenolic acids identified by HPLC analysis, and total phenolic acid as determined by the Folin Ciocalteu s phenol reagent method. 

Con 4 Total phenolic acid content in soils was overestimated by the Folin Ciocalteu s phenol reagent because a number of other organic and inorganic substances also reduce the phenol reagent. In fact, some of these other organic compounds may have been important, if not more important, in the inhibition observed for soil extracts. 

Pro 4 Total phenolic acid concentrations estimated by water-autoclave extraction and Folin Ciocalteu s phenol reagent are not absolute values and thus should not be viewed as such, they are relative values. The following suggest that these relative values for total phenolic acid content can actually be useful and meaningful ... 

The content of total polyphenols was determined by colorimetric assay with Folin-Ciocalteu s phenol reagent, according to Singleton and Rossi 14). 

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