Phenolic reagents

One Anson unit is the amount of enzyme that, under standard conditions, digests hemoglobin at an initial rate, Hberating per minute an amount of TCA-soluble product which produces the same color with phenol reagent as one milliequivalent of tyrosine (91). 

Recently, the old alkaline phenol method has been revived, and is being widely used in clinical laboratories, without protein preclpltatlon(27). In this procedure, the serum is added to an alkaline phenol reagent, and the ammonia generated from urea is determined either after the action of urease or after strong alkaline treatment of the serum. The objection to this procedure is first, that all urease is rich in ammonia, and second, the color produced with alkaline phenol is not specific for ammonia. It will react with other compounds, especially for those that liberate ammonia. By this procedure one obtains a useful number from the point of view of determining whether the patient has nitrogen retention, but a value which is somewhere between a urea and an N.P.N. determination. 

Lowry, O.H. Rosebrough, N.J. Farr, A.L. and Randall, R.J. Protein measurement with folin phenol reagent. J Biol Chem 193 265-275, 1951. Munson, P.J.. and Rodbard, D. LIGAND A versatile computerized approach for characterization of ligand binding systems. Anal Biochem 107 220-237. 1980. 

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). 

In Goiffon s method (G3) peptides are precipitated with phospho-tungstic acid from a trichloroacetic acid filtrate. The precipitate is dissolved and color is developed by a reaction with Folins phenol reagent. This method, however, is not only specific for peptides and a separate assay of uric acid has to be made since this substance also reacts with Folin s reagent. 

Protein measurement with the Folin phenol reagent. J. ... 

Lowry, O.H., Rosebrough, N.J., Farr, A.L. and Randall, R.J. Protein measurement with Folin phenol reagent. J. Biol. 

Identification of phenolic hydroxyl groups. The groups which are neutralized by sodium hydroxide, but not by the carbonate, and which give acid-resistant methoxy groups, seem to be phenols. This was confirmed (35, 46) by the reaction with typical phenol reagents, dinitrofluoro-benzene, and p-nitrobenzoylchloride (Table VIII). 

Lowry OH, Roseborough NJ, Farr AL et al (1951) Protein measiuement with the Folin phenol reagent. J Biol Chem 193 265-275... 

D Folin-Ciacalteu s phenol reagent (stock), 1 + 1 diluted with ddH20... 

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... 

Mouse-. Groups of five male TGAC or FVB/N non-carrier mice, six to seven weeks of age, were administered 3 mg phenol (reagent grade) per animal in acetone by skin application twice per week for up to 20 weeks. A skin papilloma occurred in an exposed TGAC mouse, whereas none occurred in controls (not considered to be significant) (Spalding et al., 1993). 

The reduced phosphomolybdic/phospho-lungstic acid complex produced by this reaction is intensely blue in color. The Folin phenol reagent loses its reactivity almost immediately... 

The protocol requires that the Folin phenol reagent be added to each tube precisely at the end of the 10-min incubation. At the alkaline pH of the Lowry reagent, the Folin phenol reagent is almost immediately inactivated therefore, it is best to add the Folin phenol reagent at the precise time while simultaneously mixing each tube. Because it is somewhat cumbersome, it requires some practice to do the assay well. From a practical point of view, it also limits the total number of tubes that can be done in a single run. If a 10-sec interval between tubes is used, the maximum number of tubes that can be done within 10 min is 60 (10 sec/tube x 60 tubes = 600 sec or 10 min). 

Heating 190 with an excess of phenol or another phenolic reagent in the presence of one equivalent of the corresponding sodium phenolate gives a mixture of 2-aryloxyquinoxaline 197 and benzofuro[2,3-7>]qiiinoxaline 198 (Scheme 59) (01JHC901). The latter usually prevails. 

Lowry OH, Rosebrough NJ, Farr AL, Randall RJ (1951), Protein measurement with the folin phenol reagent, J. Biol. Chem. 193 265-275. 

Figure 8. Tracings of TLC separations of the homologs of gingerol and shogaol. Conditions of separation for Spots 1 and 2 according to (40) 3 and 4 according to (42) 5, 6, ana 7 according to (43). Spots 2, 4, and 6 sprayed with phenol reagent 7 sprayed with 2,4 DNPH reagent spots 1, 3, and 5 cochromatographed spots,...

Since the ketohexoses are easily converted into 5-hydroxymethyl-2-furaldehyde, a variety of qualitative colorimetric tests have been developed for the detection of this intermediate, using phenolic reagents. Although these tests have been applied to L-sorbose74-80 they would likewise be applicable to psicose and tagatose they merely serve, however,... 

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. 

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