Assays resorcinol

Pulp Manufacture. Sodium sulfite is utilized in neutral semichemical pulping, acid sulfite pulping, high yield sulfite cooling, and some kraft pulping processes (339). Many pulp mills prepare their own sulfite and recycle as much as possible, but use of merchant sodium sulfite by pulp mills is substantial. Much of the by-product sodium sulfite from resorcinol manufacture goes into pulp appHcations as well as a substantial fraction of the lower assay manufactured sodium sulfite. 

Resorcinol was not genotoxic in bacterial assays or in in vivo mammalian assays it did cause chromosomal aberrations in human lym-phoqn es in vitro but not in cultured human fibroblasts. ... 

Resorcinol is water-soluble and readily conjugated and eliminated. The chemical has no known potential for formation of electrophilic reactive intermediates comparable to those derived from the other dihydroxybenzenes. Resorcinol was tested in various genetic toxicology assays, including in-vitro bacterial and mammalian assays and in-vivo mammalian assays. It gave negative results in all studies, with the exception of a positive response in the two in-vitro studies that assessed chromosomal aberrations in human lymphocytes from whole blood cultures however, resorcinol did not induce chromosomal aberrations in human fibroblasts. 

Naphthalene- and anthracene-derived phenols did, however, almost uniformly precipitate (Table VI). In natural materials (not grapes or wines) which contain them they would be included in the formaldehyde precipitable group. Several primary amines capable of SchifFs base formation reacted with formaldehyde to lose their F-C oxidizability, but only the resorcinol analog, 3-aminophenol, precipitated (Table VIII). Sulfite also reacted but did not precipitate with formaldehyde, and the F-C oxidizability was suppressed (Table IX). The resorcinol derivative, 2,4-dimethoxycinnamic acid, formed a precipitate with formaldehyde, but it did not react appreciably in the F-C assay. 

A good example of a back titration involving iodine and thiosulfate is the assay of resorcinol in Resorcinol Solution BP. Resorcinol is an antiseptic that was widely used in the past, although less so now. The assay of resorcinol involves a quantitative electrophilic aromatic substitution reaction using bromine as the reagent, as shown in Figure 6.4. 

The calculation of the content of resorcinol in the solution is identical to the back titration method explained above for lithium carbonate. Consequently, the volume of added bromate is modified by the bromate factor and the thiosulfate titre volume is modified by the thiosulfate factor. A blank titration is not required for this assay since no heating or cooling of the reaction is involved. 

Polyketide synthase enzyme assays contained 100 mM potassium phosphate buffer (pH 7.0), 40 pM malonyl-CoA, 25 pM starter molecule (i.e. palmitoyl-CoA), and 2 pg protein in a 200 pL volume at 30° C for 30 minutes. Reactions were quenched by addition of 10 pL of 20% HCl. The lipid resorcinol products were extracted by phase partitioning with 1 ml of ethyl acetate. The organic phase (upper layer) obtained by centrifugation at -14,000 x g for 1 minute was transferred to a fresh tube, dried under vacuum, and subsequently analyzed by GC/mass spectrometry as a trimethysilyl derivative. Product formation was quantified using selected ion monitoring at m/z 268, a common fragment to all... 

The search of the in-house virtual library identified more than 1,000 compounds containing the resorcinol substructure that were assessed for fit to the Nt-Hsp90 active site. Some 225 compounds were selected, of which 170 were delivered and assayed. Some of these compounds are shown in Table 1. Not only did this approach retrieve the same resorcinol 7 found by virtual and experimental screening [31] and encouraged us to generate additional SAR around the resorcinol-pyr-azole template (compounds 21-25), it also identified isoxazole (26-28) replacements for the pyrazole, which were explored in lead optimisation. 

The condensation reaction may take place at position 6 or 8. Position 6 of the flavan skeleton is favored because it is usually less sterically hindered than position 8. In contrast to the proanthocyanidin assay the condensation reaction runs without depolymerization of the proanthocyanidins [135]. Consequently monomers also react [116] and a multitude of different dyes are produced depending on the complexity of the sample. The maxima of the chromophores of the resulting dyes are not influenced by the B-ring hydroxylation pattern (i.e. procyanidin-prodelphinidin ratio) like in the proanthocyanidin assay [116]. Absorbances are however influenced by the substitution pattern on the ring at which condensation takes place. Condensation products of phloroglucinol nucleis show absorbance maxima at about 500 nm, whereas resorcinol and pyrogallol nucleis exhibit absorbance maxima around 520 nm [77]. 

Fig. 4.5.10. Elution profile of total gangliosides from beef brain on DEAE-silica gel (acetate form) [93]. Bed dimensions 60x2 cm. Sample applied, 40 mg ganglioside mixture. Flow-rate 1.5 ml/min. Eluents methanol, 0.2 M ammonium acetate in methanol and 0.5 M ammonium acetate in methanol gradient elution. Fractions of 15 ml were collected. Resorcinol assay method for detection of sialic acid. Mono- to tetra- denote the numbers of sialic acid residues in the ganglioside fractions. The gangliosides were isolated after removal of ammonium acetate by dialysis against cold water.

Sucrose concentrations in the medium and In cal 11 were measured by a colorimetric method using the resorcinol reaction. The assays were performed after acid hydrollsis. 

Baskettter DA, Sanders D, Jowsey IR (2007) The skin sensitization potential of resorcinol experience with the local lymph node assay. Contact Dermatitis 56(4) 196-200... 

Brief oxidation with 0.025 M-sodium metaperiodate at pH 7, followed by estimation with the resorcinol or thiobarbituric acid reagent, has been used in the simultaneous assay of free and ketosidically bonded sialic acids, respectively." Treatment of 2-acetamido-2-deoxy-3,4 5,6-di-O-isopropylidene-aW liydo-D-glucose (192) or the analogous D-mannose derivative with alkali gave 2-acetamido-2,3-dideoxy-5,6-0-isopropylidene-a-D-eryt/iro-hex-2-enofuranose (193), which afforded the methyl 2-enofuranosides (194) with acidified methanol-acetone (194)... 

The periodate oxidation of 9-O-acetyl and 4,9-di-O-acetyI derivatives of the methyl ester of 7V-acetyl-)8-D-neuraminic acid methyl glycoside has been studied the 9-O-acetyl group was found to hinder the oxidation, thus accounting for the low molar absorbancy coefficient of such derivatives in the periodate-thiobarbituric acid assay. The reactivity of a seven-carbon analogue of AT-acetylneuraminic acid, namely 5-acetamido-3,5-dideoxy-L-ara //io-heptulosonic acid, in the thiobarbituric acid and resorcinol assays has also been evaluated and the formation of the various chromophores discussed. ... 

The reactivity of 5-acetamido-3,5-dideoxy-L-flra6/7io-2-heptulopyranosonic acid (a seven-carbon analogue of iV-acetylneuraminic acid) in the resorcinol and thiobarbituric acid procedures - which are commonly used for the determination of sialic acids - has been evaluated. The chemistry involved in the formation of the characteristic chromophores in these assays was also discussed. 

Reports of sialic acids in plants exist in the literature (Mayer et al. 1964, Onodera et al. 1966), but the analytical methods employed were insufficient to exclude other compounds such as 2-keto-3-deoxy acids noted earlier in this chapter. Several investigations produced negative results, although a reaction in the periodic acid/thiobarbituric acid assay was obtained. The compounds in question gave no colour in the direct Ehrlich, orcinol/Fe and resorcinol assays for sialic acids (Gielen 1968, Cabezas 1968, 1973, CABEZAsand Feo 1969, Unger 1981). 

Those colorimetric methods developed at this time and found to be suitably sensitive and specific are the orcinol and resorcinol methods (see II. 1 below) and the periodic acid/thiobarbituric acid assay (see II. 2). These methods together with a recently introduced assay using methyl-3-benzothiazolinone-2-hydrazone and fluorimetric methods (II. 3 and II. 4, respectively) form the basis of currently used techniques. 

The method has advantages over the resorcinol and orcinol assays by virtue of its sensitivity and flexibility in determining free and bound sialic acid, and also in the lower level of interference from other monosaccharides and other substances (JOURDIAN tz/. 1971). 

The level of 0-acylation of sialic acids can also be quantitated by difference measurements with the periodic acid/thiobarbituric acid method (Neuberger and Ratcliffe 1972, Skoza and Mohos 1976, Sarris and Palade 1979, see section II. 2), with the periodate/resorcinol (II. 1. b)p)) and the MBTH method (II. 3), and a fluorimetric method (Shukla and Schauer 1981, II. 4). Using such assays care should be taken to run suitable controls for the saponification step and to consider... 

Several laboratories have reported automated procedures for the quantitation of sialic acid in biological fluids, column effluents or for miscellaneous samples. The periodic acid/resorcinol assay has been adapted for use in a Technicon autoanalyser for routine assay of serum sialic acid (Rey et al. 1975). The method is based on the assay developed by Jourdian et al. (1971) and does not involve the organic solvent extraction. As with the original assay, the automated procedure can be adapted to measure free or glycosidically bound sialic acid (Reyc/ al. 1975). Modification of this system allows measurement of erythrocyte membrane sialic acid simultaneously with protein (Gerbaut et al. 1978). 

The bathochromic shift which occurs in the spectra of many phenolic compounds with change of pH may be used as the basis of a simple spectro-photometric assay (AE method) when they are present in complex formulations. A pre-requisite of the method is the absence of spectral changes of the other constituents under the same conditions. The method has been adapted by Elvidge and Peutrell for the determination of hexachloro-phane and other phenols (phenol, resorcinol, cresol and methyl hydroxy-benzoate) in various pharmaceutical products. 

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