Hydrogen peroxide Riboflavin

Ascorbate is known to act as a water-soluble antioxidant, reacting rapidly with superoxide, hydroxyl and peroxyl radicals. However, reduced ascorbate can react non-enzymatically with molecular oxygen to produce dehydroascorbate and hydrogen peroxide. Also, ascorbate in the presence of light, hydrogen peroxide and riboflavin, or transition metals (e.g. Fe, Cu " ), can give rise to hydroxyl radicals (Delaye and Tardieu, 1983 Ueno et al., 1987). These phenomena may also be important in oxidative damage to the lens and subsequent cataract formation. 

Riboflavin is the redox component of flavin adenine dinucleotide FAD. It is derived from FAD by hydrolysis of a phosphate ester link. The fully oxidised form of FAD is involved in many dehydrogenaze reactions during which it is converted to the fully reduced form. The fully oxidised state is restored either by another redox enzyme or by interaction with oxygen and hydrogen peroxide is liberated. The one-electron reduced, semiquinone form of FAD, is involved in some electron transfer steps. 

Riboflavin (vitamin Bj) is chemically specified as a 7,8-dimethyl-10-(T-D-ribityl) isoalloxazine (Eignre 19.22). It is a precnrsor of certain essential coenzymes, such as flavin mononucleotide (FMN) and flavin-adenine dinucleotide (FAD) in these forms vitamin Bj is involved in redox reactions, such as hydroxylations, oxidative carboxylations, dioxygenations, and the reduction of oxygen to hydrogen peroxide. It is also involved in the biosynthesis of niacin-containing coenzymes from tryptophan. 

Solid-phase extraction is routinely used to clean up extracts prior to quantitation (19,42,70, 80-82). Alternatively, endogenous fluorescent artifacts in food samples can be eliminated by oxidation with potassium permanganate/hydrogen peroxide/sodium metabisulphite. Benzyl alcohol has been used to extract riboflavin selectively without the coenzymes, permitting the determination of free riboflavin. 

Pyridoxine Hydrochloride, USP. Pyridoxine hydrochloride.. S-hydroxy-6-methyl-3.4-pyridinedimethanol hydrochloride. vitamin B, hydrochloride, rat antidermatitis factor. is a white, odorless, crystalline substance that is soluble l .S in water and 1 100 in alcohol and in.soluble in ether. It is relatively. stable to light and air in the solid form and in acid solutions at a pH no greater than S. at which pH it can be autoclaved at IS pounds at I20°C for 20 to 30 minutes. Pyridoxine is unstable when irradiated in aqueous solution.s at pH 6.8 or above. It is oxidized readily by hydrogen peroxide and other oxidizing agents. Pyridoxine is as stable in mixed vitamin preparations as riboflavin and nicotinic acid. A 1% aqueous solution has a pH of 3. The pK i values fur pyridoxine. pyridoxal. and pyridoxamine are S.OO. 4.22. and 3.40. respectively, and their pK 2 values are 8.96. 8.68. and 8.05. respectively. 

No active substance could be detected in plants treated with carboxin six weeks after the treatment. The major part of the residue found was sulfoxide. Actually, sulfoxide can occur in the plant in two ways. On the one hand, carboxin is oxidised relatively rapidly in the soil, and the plant takes up its sulfoxide, and, on the other hand, carboxin is metabolised within the plant to sulfoxide, presumably by enzyme systems producing hydrogen peroxide, such as riboflavin or flavin enzymes (Lyr et al., 1975a). It has been proved by extraction with hot dimethyl sulfate that sulfoxide formed in the plant is gradually bound in the form of a water-insoluble complex to lignin and is thus detoxified. No hydrolysis of carboxin in the plant has been observed (Chin et al., 1973). 

Superoxide dismutase will scavenge the Of formed and will therefore inhibit the reduction of the dianisidine radical by Of. Consequently the dianisidine radical will dismute to yield the divalently oxidized dianisidine. In the presence of superoxide dismutase this reaction is augmented (Fig. 6). The possibility that Of could reduce the final product of dianisidine oxidation and reverse the change in absorbance at 460 nm was tested and was excluded. The assay has been used to determine the rate constant for purified swordfish liver copper/zinc superoxide dismutase (Bannister et al., 1979) and could be applied to crude extracts. The assay was also found applicable to polyacryalmide gels (Misra and Fridovich, 1977c). Gels soaked in riboflavin plus dianisidine, and subsequently illuminated, developed stable brown bands. Peroxidases are also stained by this procedure due to the photochemical production of hydrogen peroxide. However, the development of bands due to peroxidase activity is much slower than the development of bands due to dismutase activity. 

Aminomethyl propanol Hydrogen peroxide solubilizer, resins aq. coatings 2-Dimethylamino-2-methyl-1-propanol solubilizer, riboflavin Pyridine-3-methanol solubilizer, rinse aids... 

Applebaum, R.S. and Marth, E.H. (1982). Inactivation of afla-toxin H. in milk using hydrogen peroxide and hydrogen peroxide plus riboflavin or lactoperoxidase. J. Food Protection. 45, 557-560. 

Generally, AA is determined individually, and only about a 10% of the published methods determine AA simultaneously with other analytes such as uric acid, glucose, fructose, dopamine, iodate, bromate, hypochlorite, thiourea, glutathione, hydrogen peroxide, acetylsalicylic acid, kojic acid, ascorbyl glucoside, paracetamol, cysteine, and other water soluble vitamins (thiamine [vitamin Bj], folic acid [vitamin B12], niacin [vitamin B3], riboflavin [vitamin B2], and pyridoxine [vitamin B ]). 

III) and urea (II), the quinoxalinecarboxylic acid (III) is decarboxylated to 1-ribityl-l, 2-dihydro-2-keto-6,7-dimethylquinoxaline (IV), which in turn is oxidized to l-ribityl-2,3-diketo-l, 2,3,4-tetrahydro-6,7-dimethylquinoxaline (V). The first two of these proposed reactions would correspond to the chemical degradation of riboflavin or lumiflavin by dilute alkali and heat (cf. Fig. 1, A, B, C). Preliminary experiments with the appropriate quinoxalinecarboxylic acid and its lactam did not lead to their conversion to l-ribityl-2,3-diketo-l,2,3,4-tetrahydro-6,7-dimethylquinoxaline, although the chemical oxidation by hydrogen peroxide of 1-ribityl-l,2-dihydro-2-keto-6,7-dimethylquinoxaline-3-carboxylic acid has been indicated to occur. As a result, the possibility has been considered that products other than those pictured resulting in compounds (III) and... 

The effects of photosensitizers on the formation of free radicals on u.v.-irradiation of cellulose at 77 K have been investigated. Samples of cellulose treated with benzoyl peroxide, hydrogen peroxide, benzophenone, riboflavin, Cr + ions, or Ni + ions exhibited single-line e.s.r. spectra, whereas those treated with Pb + or Fe + ions exhibited three- and five-line e.s.r. spectra, respectively. Studies of the decay of radicals in photo-irradiated cellulose at low temperatures indicated that at least six types of radical are formed. Changes in the radicals with the reaction conditions were carefully examined. 

Another chemiluminescent system containing copper-II- ions, riboflavin, hydrogen peroxide, and mercaptoethanol [53] appears to proceed via a similar mechanism, H02 radicals being intermediates. 

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