Tests orcinol

The 3- and 5-phosphates of D-ribose are readily distinguishable. Levene and Stiller91 showed that the 3-isomer hydrolyzes much more rapidly in acid solution than does the 5-isomer a colorimetric method for distinguishing the two isomers, based on the rate of color development in the orcinol test for pentoses, has more recently been described by Albaum and Umbreit.131... 

Carbohydrates have long been thought to be associated with the nucleic acid of the bacilli. Bendix ° prepared from the intact cell a nucleoprotein fraction which, after hydrolysis, yielded derivatives which were reducing to Fehling solution and gave a green coloration in the orcinol test. Bendix thus claimed that pentoses were present in the nucleoprotein of M. tuberculosis. 

Like their parent nucleosides, uridylic and cytidylic acids give only a faint orcinol test owing to the stability of the union between sugar and pyrimidine. In addition, the phosphoryl group adheres to the pentose... 

It was found that carbazole and phloroglucinol are unsuitable for determining the heptose content of sugar mixtures because of interference from other sugars similar interference is encountered with resorcinol. With orcinol, cysteine, and diphenylamine, however, specific reactions can be obtained at selected wavelengths. Ketoheptoses (and keto sugars in general) react under milder acid conditions than the aldoses, and this property can be used for identification purposes. In the orcinol test, for... 

This work was continued by Dickens, who also used a fraction from autolyzed yeast, TPN, and as the autoxidizable hydrogen carrier, phenazine or a flavoprotein system. Dickens isolated various products, one of which appeared to be a mucture of a phosphopentonic acid and a phosphoketohexonic acid, and others analyzed as 5- and 4-carbon phosphate esters. The 5-carbon compound gave a reaction in the Bial FeClj-orcinol test which was characteristic of pentose. In general, the enzyme preparations of this period did not yield simple reaction products, nor were the methods available for the separation and characterization of the small amounts of products which were isolated. For instance, although suggestions were obtained of the presence of pentose in the products, this was not unequivocally demonstrated. 

Primary Alcohols. Neubauer (299), using tests of doubtful reliability (orcinol test, reducing value and polarimetry), reported that ethyl, n-propyl, ft-butyl, isobutyl, n-octyl and isopentyl alcohols cause increased excretion of glucuronic acid in both the rabbit and the dog, the response being more pronounced in the rabbit. On the contrary, methyl alcohol apparently did not increase glucuronic acid production. 

By careful choice of both the reaction conditions and the phenolic compound used, it may be possible to produce a colour that is characteristic of a particular carbohydrate or related group, so giving some degree of specificity to the method. Thus, Seliwanoff s test uses hydrochloric acid and either resorcinol or 3-indolylacetic acid to measure fructose with minimal interference from glucose. The colour produced by pentoses with orcinol (Bial s reagent) or p-bromoaniline is sufficiently different from that produced by hexoses to permit their quantitation in the presence of hexoses. However, none of the methods based on the formation of furfural or its derivatives can be considered to be entirely specific. 

Chlorinated orcinol derivatives have been isolated from diseased bulbs of the edible lily Lilium maximowiczii. The antifungal activity of these compounds was tested against Bipolaris leersiae. Inhibition of the conidial germination depends on the number of chlorine atoms in the compounds. The trichlorinated orcinol 156 shows the highest activity. Dichlorinated orcinols, e.g. 157, are next, and the monochlorinated ones, e.g. 158, are still less active. The nonchlorinated orcinol shows lowest activity [121]. 

Attempts have been made to estimate 2-desoxyribose by the orcinol reaction94-97 for pentoses, but in the test the desoxysugar is mainly converted into levulinic acid which gives no color with the reagent. Consequently, in tests for nucleic acids the intensity of the color given by desoxyribonucleic acid corresponds to only about one eighth of that obtained with the same quantity of ribonucleic acid.46 50-98... 

The reaction of hemicellulose to heated, concentrated (12%) HC1 is a test of the former s presence. Detection is by the violet or red color developed by one or more of the reaction products (chiefly furfural) with orcinol or phloroglucinol. The coloration is either blue, greenish, or nonexistent with KI-I2 (Whistler and Smart, 1953). The quantity of furfural produced relates directly to the quantity of pentosan present (Smith and Montgomery, 1959). Under the same reaction conditions, hexoses produce hydroxyme-thylfurfural. Furfural is steam-distillable hydroxymethylfurfural is not. 

If a protein does not contain hexosamines, one other test for the presence of neutral sugars should be made. This can be done by paper chromatography (Carsten and Pierce 1963 Spiro 1965) or gas chromatography ( 2.13.3) after appropriate hydrolysis ( 2.13.2), or a simple colorimetric reaction, such as the orcinol method (below), may be used. 

Although several colorimetric methods have been developed in the past, only two main procedures are currently routinely applied, namely the orcinol/Fe /HCl assay, known as the Bial reaction, and the periodie acid/thiobarbituric acid assay. For microadaptations of these two different tests, see ref. [11]. 

An extensive study has been devoted to the orcinol-sulfuric acid reagent, resulting in a highly specific reagent for D-fructose the test solutions are heated at 100° for only 50 seconds, and 31.2 N acid is used. "... 

The orcinol reaction (Al) is simple, and further evidence of identification can be gained by determining the absorption spectrum of the color obtained by the reaction. The reaction is not specific for pentoses. Bial s test (HI) for pentoses in the urine represents the qualitative version of this reaction. 

The formation of colored products by the reaction of sugars and phenols in the presence of strong acids has been mentioned previously as a qualitative test for carbohydrates. Carbazole or anthrone may be used instead of a phenol. Methods employing orcinol (3,5-dihydroxy toluene) and carbazole have been described in detail 31). Dische 32) described a modified carbazole reaction for determining ketohexoses, ketopentoses, trioses, and glycolic aldehyde as well as a method for determining heptoses. 

The same scheme was further used to select likely co-crystal formers for artemisinin. Only two of the 75 compounds tested experimentally gave a co-crystal, orcinol and resorcinol (Formula 5.2). The difficulty of rationalising co-crystal formation with artemisinin is illustrated by the fact that the structures and supramolecular motifs in the two resulting co-crystals show almost no structural similarity, except the existence of O-H O hydrogen bonds. Yet, both orcinol and resorcinol were among the 41 likely co-formers (56%). 

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