6-Dichlorophenolindophenole

Chemical Properties. The most significant chemical property of L-ascorbic acid is its reversible oxidation to dehydro-L-ascorbic acid. Dehydro-L-ascorbic acid has been prepared by uv irradiation and by oxidation with air and charcoal, halogens, ferric chloride, hydrogen peroxide, 2,6-dichlorophenolindophenol, neutral potassium permanganate, selenium oxide, and many other compounds. Dehydro-L-ascorbic acid has been reduced to L-ascorbic acid by hydrogen iodide, hydrogen sulfide, 1,4-dithiothreitol (l,4-dimercapto-2,3-butanediol), and the like (33). 

Because of the time and expense involved, biological assays are used primarily for research purposes. The first chemical method for assaying L-ascorbic acid was the titration with 2,6-dichlorophenolindophenol solution (76). This method is not appHcable in the presence of a variety of interfering substances, eg, reduced metal ions, sulfites, tannins, or colored dyes. This 2,6-dichlorophenolindophenol method and other chemical and physiochemical methods are based on the reducing character of L-ascorbic acid (77). Colorimetric reactions with metal ions as weU as other redox systems, eg, potassium hexacyanoferrate(III), methylene blue, chloramine, etc, have been used for the assay, but they are unspecific because of interferences from a large number of reducing substances contained in foods and natural products (78). These methods have been used extensively in fish research (79). A specific photometric method for the assay of vitamin C in biological samples is based on the oxidation of ascorbic acid to dehydroascorbic acid with 2,4-dinitrophenylhydrazine (80). In the microfluorometric method, ascorbic acid is oxidized to dehydroascorbic acid in the presence of charcoal. The oxidized form is reacted with o-phenylenediamine to produce a fluorescent compound that is detected with an excitation maximum of ca 350 nm and an emission maximum of ca 430 nm (81). 

Dipping solution Dissolve 40 mg 2,6-dichlorophenolindophenol sodium in too ml ethanol. 

Because of the clinical significance of vitamin C, it is essential to In-able to detect and quantify its presence in various biological materials. Ana lytical methods have been developed to determine the amount of ascorbic acid in foods and in biological fluids such as blood and urine. Ascorbic acid may be assayed by titration with iodine, reaction with 2,4-dinitrophenylhy-drazine, or titration with a redox indicator, 2,6-dichlorophenolindophenol (DCIP) in acid solution. The latter method will be used in this experiment because it is reasonably accurate, rapid, and convenient and can be applied to many different types of samples. 

Electron mediators are usually organic molecules that are redox active, such as ferrocene derivatives, benzoquinone, N-methylphenazium, and 2,6-dichlorophenolindophenol (DCPIP). Ferricyanide has also been used as an electron mediator. They offer the advantages of non-... 

The oxidation of the enamine on El in PDHc by nonlipoic acid acceptors has also been explored for many years. For example, ferricyanide reduction monitored by visible spectroscopy has become a standard test to assay El activity, notwithstanding the attendant problems, including the instability of the thiazolium ring to such conditions. 2,6-Dichlorophenolindophenol (DCPIP) has also been used as an alternative electron acceptor in mechanistic studies of PDHcs75. 

Dichlorophenolindophenol choline dehydrogenase and, 261 cytochrome 6j and, 267 cytochrome P-450 reductase and, 167 a-glycerophosphate dehydrogenase and,... 

Table 1 Summary of respiratory chain, complex V and PDHc activity assays. All assays are spectrophotometric assays except for the PDHc assay with CO2 detection, which is a radiochemical assay. The specific inhibitor indicated is used for blank measurements. Non-standard abbreviations UQi nbiquinone-Qi DQ decylubiquinone DCIP 2,6-dichlorophenolindophenol, PK pyruvate kinase LDH lactate dehydrogenase AABS / -[p-(aminophenyl)azo]benzene sulfonic acid ArAt arylamine acetyltransferase...

Often, sugar acids can be detected with Congo Red indicator, and ascorbic acid with 2,6-dichlorophenolindophenol. 

The mediated OTTLE/Nernst method, with 2,6-dichlorophenolindophenol as mediator, was employed by Heineman et al. in the measurement of E for cytochrome c [83], For enzymes, the mediated OTTLE/Nernst method is probably the method of choice, since the heterogeneous charge-transfer processes often are very slow the electroactive metal center is insulated by the surrounding protein structure and cannot get close to the electrode surface. 

The sodium salt of 2,6-dichlorophenolindophenol, N-(3,5-dichloro-4-hydroxyphenyl)-p-benzoquinone imine (Tiibnan reagent), is used especially in steroid chemistry for the conversion of a-hydroxy ketones into a-hydroxy acids and a-keto acids [976] (equation 20). 

Evidence for the production of ascorbic acids is that, after irradiation, the solution was able to decolorize solutions of 2,6-dichlorophenolindophenol and to produce a red color with an alkaline solution of triphenyltetrazolium chloride. The solution also displayed an absorption maximum at 245 m/u similar to that of L-ascorhic acid, and paper chromatography indicated the presence of a product running identically with L-ascorbic acid. The yield of the ascorbic acid was a function of the concentration, rising from G 0.16 at 5 X 10 ilf to G 0.95 at 4 X 10 M for a dose of 2.8 X 10 e.v. ml. of x-rays. The route to the ascorbic acid from the lactone may involve abstraction of a hydrogen atom at C-2 or C-3, followed by enoliza-tion. 

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