<b>The Photochemical Degradation of Riboflavin</b>

Smith, Eddie C.; Metzler, David E.

doi:10.1021/ja00903a051

Cited by 119 publications

(46 citation statements)

References 26 publications

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“…The products detected in this study are known and have previously been identified in the photolysis of RF and FMF (an intermediate in this reaction) by Smith and Metzler, 39) Treadwell et al 40) and Ahmad et al 5,12,14,38) The confirmation of the products formed on the photolysis of RF in the presence of caffeine is necessary to carry out the assay of RF and the photoproducts in degraded solutions. The intensity of the spots of the photoproducts in degraded solutions appeared to decrease with an increase in the concentration of caffeine indicating its inhibitory effect on the rate of photolysis of RF in the pH range studied.…”

Section: Resultssupporting

confidence: 58%

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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1363Riboflavin is a highly photosensitive compound and is degraded in aqueous solution by several mechanisms [1][2][3] including intramolecular photoreduction 4,5) and intramolecular photoaddition. [6][7][8][9] These reactions are affected by pH, 4,5,[10][11][12] solvent polarity and viscosity, 13,14) ionic strength, 15) buffer kind and concentration [6][7][8][9]16) and light intensity and wavelengths. [6][7][8][9]17) Various methods including the use of photostabilizers, incorporation into liposomes and cyclodextrin complexation have been used to stabilize riboflavin solutions in the presence of light. [18][19][20][21] Another approach to achieve stabilization of drugs is through complexation with caffeine and other agents. [22][23][24][25][26] Riboflavin is known to form molecular complexes with caffeine [27][28][29][30][31][32] which has been found to influence the rate of its chemical 33) and photochemical degradation.17) Riboflavin-caffeine complexation may improve the bioavailability 34) and therapeutic activity 35) of the vitamin. NMR studies have been conducted to understand the nature of association between caffeine and flavin mononucleotide 36) that may help in the understanding of the mode of riboflavin stabilization. The present work is based on a detailed study of the kinetics of riboflavin photolysis in the presence of caffeine over a wide range of pH using a specific multicomponent spectrophotometric method 12) for the determination of riboflavin and photoproducts. The kinetic data have been used to determine the stability constants for riboflavin-caffeine complex. The quantitative and kinetic evaluation of such interactions may suggest the possibility of achieving the stabilization of photolabile compounds and thus enhance their biological action. The chemical structures of riboflavin, its photoproducts and caffeine are shown in Fig. 1. ExperimentalThe materials and methods used are the same as previously described for a similar study.5) The photolysis of 5ϫ10 Ϫ5 M riboflavin (RF) solutions was carried out in the presence of 0.5-2.5ϫ10Ϫ4 M caffeine using a Philips HPLN 125 W high pressure mercury vapor fluorescent lamp (emission at 405 and 435 nm) 9) as the irradiation source. The spectral measurements on RF and degraded solutions were performed on a Shimadzu UV-1601 recording spectrophotometer using silica cells of 10 mm path length. The intensity of the fluorescent lamp was determined by potassium ferrioxalate actinome- The effect of caffeine complexation with riboflavin on the kinetics of riboflavin photolysis in the pH range 2.0-10.5 has been studied. The photolysis of riboflavin solutions (5؋10 ؊ ؊5 M) was carried out in the presence of caffeine (0.5-2.5؋10 ؊ ؊4 M) using a visible radiation source. A specific multicomponent spectrophotometric method was used for the determination of riboflavin and photoproducts in photolysed solutions. The apparent first-order rate constants (k) for the photolysis reactions range from 2.71؋10 ؊4 to 4.26؋10 ؊2 min Effect of Caffeine Complexation on the Photol...

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Section: Resultssupporting

confidence: 58%

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…It was shown that when samples were removed after 17 and 24 h of irradiation, the colour was restored upon admission of air in 89% and 84%, respectively. 35 The same mechanism may work in our experimental conditions to keep a high level of RF concentration in the solution. Simultaneously, a small decrease in the pH of the irradiated solutions with the increase in the irradiation time was observed.…”

Section: Resultsmentioning

confidence: 75%

“…30,35 It was observed that the concentration of RF decreased with the increase of irradiation time, producing a series of products that were carefully identified. 30,31,54,55 In particular, when anaerobic conditions were used and air was admitted to the partially bleached solution, reoxidation of the isoalloxazine ring occurred as was indicated by the important recovery of the original absorption at 445 nm and the return of the yellow colour.…”

Section: Resultsmentioning

confidence: 99%

“…16,28 In particular riboflavin (RF) photochemistry, the precursor of all the biologically important flavins and recognised as a constituent of the vitamin B complex, has been extensively investigated. 27,[29][30][31][32][33][34][35] It was even hypothesised that water can be split photochemically with RF. 34 The photochemistry of RF involves two major reactions: (i) normal photolysis (intramolecular photoreduction) and (ii) photoaddition (intramolecular photoaddition).…”

Section: Introductionmentioning

confidence: 99%

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Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO₂Nanotubes

Backes

Scheffer

Pereira

et al. 2014

Journal of the Brazilian Chemical Society

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A degradação de soluções aquosas de índigo carmim (IC), azul de metileno (MB) e laranja de metilo (MO) assistida pela luz visível foi conseguida sobre a superfície de nanotubos (NTs) de TiO 2 impregnados com riboflavina (RF). Soluções aquosas diluídas de RF na presença de RF-NTs TiO 2 irradiados com luz UV produziram O 2 , CO e CO 2 como principais produtos gasosos. As mesmas soluções quando irradiadas com luz visível mostraram que o O 2 foi o produto principal obtido. Esta geração de O 2 in situ com luz visível permite a degradação dos corantes, sem a necessidade de borbulhar ar ou oxigênio no sistema de reação. A degradação fotocatalítica de MO, MB e IC pode ser descrita por um modelo de cinética de pseudo-primeira ordem obtendo ca. 100% de degradação de MB, MO e IC em menos de 3 h de iluminação de luz visível. Os resultados aqui apresentados são altamente promissores em vista da potencial aplicação dos catalisadores RF-TiO 2 NTs preparados com dois compostos ambientalmente corretos na degradação de poluentes utilizando radiação solar.Visible light-assisted degradation of indigo carmine (IC), methylene blue (MB) and methyl orange (MO) aqueous solutions has been achieved on the surface of TiO 2 nanotube (NT) arrays impregnated with riboflavin (RF). Diluted RF water solutions in the presence of RF-TiO 2 NTs irradiated with UV light produced O 2 , CO and CO 2 as main gas products. On the contrary, the same solutions irradiated with visible light evolved O 2 as a main product. This in situ O 2 generation under visible light absorption allows the degradation of the dyes without the necessity to bubble air or oxygen in the reaction system The photocatalytic degradation of MO, MB and IC can be described by a pseudo-first-order kinetic model obtaining ca. 100% degradation of MB, MO and IC in less than 3 h of visible light illumination. The results provided here are highly promising in view of various photocatalytic applications of the prepared RF-TiO 2 NTs catalysts by two environmentally friendly compounds in the degradation of pollutants using solar radiation.

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“…RF (pK a1 , 1.7) (47) exists 99% in the neutral form at pH 3.8-5.6 and, therefore, the decrease in the rate is not due to any change in the ionized state of the molecule. The photolysis of RF in aqueous solution basically involves intramolecular photoreduction of the isoalloxazine ring followed by cleavage of the ribityl side chain to produce FMF and subsequent photoproducts (LC, LF) (17,18,44,48,49). The decrease in the rate of RF photolysis could be ascribed to the redox behavior of RF in the pH range 3.8-5.6.…”

Section: Acid Range (Ph 38-56)mentioning

confidence: 99%

Effect of Acetate and Carbonate Buffers on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

et al. 2014

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Abstract. The photolysis of riboflavin (RF) in the presence of acetate buffer (pH 3.8-5.6) and carbonate buffer (pH 9.2-10.8) has been studied using a multicomponent spectrophotometric method for the simultaneous assay of RF and its photoproducts. Acetate and carbonate buffers have been found to catalyze the photolysis reaction of RF. The apparent first-order rate constants for the acetate-catalyzed reaction range from 0.20 to 2.86 ×10 −4 s −1 and for the carbonate-catalyzed reaction from 3.33 to. The second-order rate constants for the interaction of RF with the acetate and the carbonate ions range from 2.04 to 4.33×10 −4 M −1 s −1 and from 3.71 to 11.80×10, respectively. The k-pH profile for the acetate-catalyzed reaction is bell shaped and for the carbonate-catalyzed reaction a steep curve. Both HCO 3 − and CO 3 2− ions are involved in the catalysis of the photolysis reaction in alkaline solution. The rate constants for the HCO 3 − and CO 3 2− ions catalyzed reactions are 0.72 and 1.38×10, respectively, indicating a major role of CO 3 2− ions in the catalysis reaction. The loss of RF fluorescence in acetate buffer suggests an interaction between RF and acetate ions to promote the photolysis reaction. The optimum stability of RF solutions is observed in the pH range 5-6, which is suitable for pharmaceutical preparations.

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The Photochemical Degradation of Riboflavin

Cited by 119 publications

References 26 publications

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO₂Nanotubes

Effect of Acetate and Carbonate Buffers on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

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The Photochemical Degradation of Riboflavin

Cited by 119 publications

References 26 publications

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Effect of Caffeine Complexation on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO2Nanotubes

Effect of Acetate and Carbonate Buffers on the Photolysis of Riboflavin in Aqueous Solution: A Kinetic Study

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Photosensitised Degradation of Organic Dyes by Visible Light Using Riboflavin Adsorbed on the Surface of TiO₂Nanotubes