Riboflavin, degradation

Harkness DR, L Tsai, ER Stadtman (1964) Bacterial degradation of riboflavin V. Stoichiometry of riboflavin degradation to oxamide and other products, oxidation of C " -labeled intermediates and isolation of the pseudomonad effecting these transformations. Arch Biochem Biophys 108 323-333. 

Figure 10 Catabolic pathway of riboflavin (84) (vitamin B2). Riboflavin degradation (a) catalyzed by riboflavinase, (b) under anaerobic conditions, (c) catalyzed by BluB, and (d) under aerobic conditions.

Riboflavin is one of the most stable vitamins, showing stability towards acidic pH and relatively small losses at neutral pH. Although riboflavin is rapidly degraded in alkaline pH, this condition is uncommon in food products and therefore of less concern. The typical mechanism for riboflavin degradation is... 

Total Synthesis of Hunanamycin A Hunanamycin A is a natural product isolated from a marine-derived Bacillus humanensis. This compound presents a nitrogenated tricyclic structure related to riboflavin degradation products and shows antimicrobial activity against Salmonella... 

In 1933, R. Kuhn and his co-workers first isolated riboflavin from eggs in a pure, crystalline state (1), named it ovoflavin, and deterrnined its function as a vitamin (2). At the same time, impure crystalline preparations of riboflavin were isolated from whey and named lyochrome and, later, lactoflavin. Soon thereafter, P. Karrer and his co-workers isolated riboflavin from a wide variety of animal organs and vegetable sources and named it hepatoflavin (3). Ovoflavin from egg, lactoflavin from milk, and hepatoflavin from Hver were aU. subsequently identified as riboflavin. The discovery of the yeUow en2yme by Warburg and Christian in 1932 and their description of lumiflavin (4), a photochemical degradation product of riboflavin, were of great use for the elucidation of the chemical stmcture of riboflavin by Kuhn and his co-workers (5). The stmcture was confirmed in 1935 by the synthesis by Karrer and his co-workers (6), and Kuhn and his co-workers (7). 

Larson et al. (1992) studied the photosensitizing ability of 2, 3, 4, 5 -tetraacetylriboflavin to various organic compounds. An aqueous solution containing aniline was subjected to a medium-pressure mercury arc lamp (X >290 nm). The investigators reported that 2, 3, 4, 5 -tetraacetylribofiavin was superior to another photosensitizer, namely riboflavin, in degrading aniline. Direct photolysis of aniline without any photosensitizer present resulted in a half-life of 23 h. In the presence of riboflavin and 2, 3, 4, 5 -tetraacetylribofiavin, the half-lives were 1 min and 45 sec, respectively. Photoproducts identified in both reactions were azobenzene, phenazine, and azoxybenzene. 

An aqueous solution of amitrole can decompose in the following free radical systems Fenton s reagent, UV irradiation, and riboflavin-sensitized photodecomposition (Plimmer et al, 1967). Amitrole-5- C reacted with Fenton s reagent to give radiolabeled carbon dioxide, unlabeled urea, and unlabeled cyanamide. Significant degradation of amitrole was observed when an aqueous solution was irradiated by a sunlamp (L = 280-310 nm). In addition to ring compounds, it was postulated that other products may have formed from the polymerization of amitrole free radicals (Plimmer et al., 1967). 

Photolytic. When propachlor in an aqueous ethanolic solution was irradiated with UV light (>, = 290 nm) for 5 h, 80% decomposed to the following cyclic photoproducts W-isopropyloxindole, W-isopropyl-3 hydroxyoxindole, and a spiro compound. Irradiation of propachlor in an aqueous solution containing riboflavin as a sensitizer resulted in completed degradation of the parent compound. 3-Hydroxypropachlor was the only compound identified in trace amounts which formed via ring hydroxylation (Rejtb et al, 1984). Hydrolyzes under alkaline conditions forming W-isopropylaniline (Sittig, 1985) which is also a product of microbial metabolism (Novick et al., 1986). 

The final step in riboflavin biosynthesis has been extensively investigated. Incorporation and degradation studies with synthetic (33) using cell-free systems and purified enzymes have shown that two molecules of (33) are utilized to afford one molecule of riboflavin and one molecule of (36). Significantly, the lumazine (33) labelled at the C-6 methyl with deuterium is converted to riboflavin labelled at C-5 and in the C-7 methyl. Based on this and kinetic and spectroscopic data, Plaut has proposed a detailed mechanism for the riboflavin synthetase reaction (B-71MI10402). It is noteworthy that this reaction can also be accomplished non-enzymatically under neutral conditions with the same stereospecificity observed in the enzymic reaction (69CC290). 

When taken up by the body, riboflavin is converted into its coenzyme forms (Chapter 25) and any excess is quickly excreted in the urine. Urine also contains smaller amounts of metabolites. The ribityl group may be cut by the action of intestinal bacteria acting on riboflavin before it is absorbed. The resulting 10-hydroxyethyl flavin may sometimes be a major urinary product.c d The related 10-formylmethyl flavin is also excreted,0 as are small amounts of 7a- and 8a- hydroxyriboflavins, apparently formed in the body by hydroxylation. These may be degraded farther to the 7a- and 8a- carboxylic acids of lumichrome (riboflavin from which the ribityl side chain is totally missing).6 A riboflavin glucoside has also been found in rat urine.f... 

All of the B2 vitamers are unstable at alkaline pH the coenzymes are also degraded below pH 5.0 (80 - 82). As a result, analysis of the endogenous coenzymes needs to be carried out at pH 5.0-7.0, while total riboflavin (as riboflavin) is best determined at acidic pH. Riboflavin is soluble in water and short-chain alcohols, but insoluble in ether, chloroform, and acetone. The coenzymes are water soluble. 

LF Russell, JT Vanderslice. Non-degradative extraction and simultaneous quantitation of riboflavin, flavin mononucleotide, and flavin adenine dinucleotide in foods by HPLC. Food Chem 43 151-162, 1992. 

Ishizaki K, Shinriki N, UedaT(1984) Degradation of nucleic acids with ozone. V. Mechanism of action of ozone on deoxyribonucleoside 5 -monophosphates. Chem Pharm Bull 32 3601-3606 Ito K, Inoue S, Yamamoto K, Kawanishi S (1993) 8-Flydroxydeoxyguanosine formation at the 5 site of 5 -GG-3 sequences in double-stranded DNA by UV radiation in riboflavin. J Biol Chem... 

Table 10.34. Effect of photoexcited menadione, benzophenone and riboflavin on Thd, dGuo and d(TpG). Degradation (+ = observed, - = not observed) and specific products in the case of d(TpG). (Delatour et al. 1999) ...

Lumichrome (Figure 10.1), a water-soluble degradation product of riboflavin,157 appears to be the first characterized gregarious (produced by conspecifics) cue for induction of metamorphosis of a marine invertebrate. Lumichrome is exuded into aqueous media from cultures of larvae of the ascidian Halocynthia roretzi, and was also found in the eggs, gonads, and tunic of the adults following extraction in methanol.157 Metamorphosis of larvae was induced by purified lumichrome... 

Many ascidians live gregariously, and for some of these species conspecific chemical cues may play an important role in gregarious settlement of the larvae. The extracts of conspecific adults, larvae, or their conditioned seawater have been shown to contain metamorphosis inducers which have never been characterized.74-75 Recently, Fusetani and co-workers elucidated the structure of the metamorphosis inducer for the solitary ascidian Halocynthia roretzi, which was isolated from seawater conditioned by ascidian larvae.10 The compound isolated from the medium was identical to lumichrome, a compound known to be a degradation product of riboflavin (Figure 13.1). The origin of lumichrome in //. roretzi is not known at present. 

Photosensitization for the removal of certain pollutants in photolytic processes can contribute significantly to the degradation rate. Thus, Simmons and Zepp [88] observed increases of up to 26 times of the photodegradation rates of nitroaromatic compounds due to the action of natural or commercial humic substances with solar irradiation. In another work [89], the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) was irradiated in water with 300 nm light in the presence of different photosensitizers. This compound, which does not photolyze directly at this wavelength, could be degraded more than 95% in 5 hr when riboflavin was used as photosensitizer. 

Alcohol is distilled up to a content of 96% in one or more stages. About 1 % of ethanol consists of fusel oils (degradation products of amino acids) which can be used as solvents for lacquers and resins. Solids from the processed liquor containing proteins, carbohydrates, mineral salts, riboflavin and other vitamins are used in poultry, swine and cattle feeds. C02 and H2 produced in butanol-acetone-butyric acid production can be used for the chemical synthesis of methanol and ammonia, or are burned. 

Tada, M., Kobayashi, N., Kobayashi, S. 1971. Studies on the photosensitized degradation of food constituents. II. Photosensitized degradation of methionine by riboflavin. J. Agric. Chem. Soc. Japan 45, 471—476. 

The effects of riboflavin or fatty acid methyl esters on the photooxidation of CHOL have been investigated (Hu and Chen, 2002 Chien et al., 2003). The data show that the presence of riboflavin or fatty acids methyl esters facilitates the degradation of CHOL and the production of OS. Riboflavin had a more pronounced effect than fatty acid methyl esters. 7-K.eto... 

SHW has also been apphed to the separation of nutraceuticals, natural products, and biochemicals, including the water-soluble vitamins, thiamine, riboflavin, and pyidoxine (Table 18-3) without significant thermal degradation. 

Figure 17 Hapten 55 elicited antibodies TD1 -10E8 and TD1-36H10 that catalyze the oxidative degradation of nicotine (53) using riboflavin as a photosensitizer.

Dickerson TJ, Yamamoto N, Janda KD. Antibody-catalyzed oxidative degradation of nicotine using riboflavin. Biooi. Med. Chem. 2004 12(18) 4981-4987. 

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