Multicomponent spectrophotometric assay of riboflavine and photoproducts

Ahmad, Iqbal; Rapson, H. D. C.

doi:10.1016/0731-7085(90)80029-o

Cited by 51 publications

(69 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2a) showed gradual disappearance of the 445 nm band with the progress of photolysis indicating the formation of the major final product, LC. This is evident from the gradual increase in absorbance at the maximum of this compound (356 nm) 12) in the chloroform extract determined at pH 4.5. An increase in the concentration of caffeine results in a slower decrease in absorbance at 445 nm in the aqueous phase indicating the inhibition of RF photolysis as a result of complexation.…”

Section: Resultsmentioning

confidence: 99%

“…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: Resultsmentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

“…[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.…”

mentioning

confidence: 99%

See 3 more Smart Citations

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

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

Self Cite

View full text Add to dashboard Cite

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...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

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

Ahmad

Ahmed

Sheraz

et al. 2009

CHEMICAL & PHARMACEUTICAL BULLETIN

Self Cite

View full text Add to dashboard Cite

show abstract

“…Ahmad et al [11] developed a multicomponent spectrophotometric method for the assay of RF, FMF, LC, LF and CDRF in the photodegradation of RF in the presence of phosphate buffer and applied it to the kinetic studies of the reaction [11][12][13][14]. Ahmad and Rapson [39] had previously reported a similar spectrophotometric method for the assay of RF, FMF, LC and LF in the photodegraded solutions of RF. This method has extensively been applied to study the kinetics of normal photolysis of RF in aqueous solution in the absence [15][16][17] and presence of CF [27].…”

Section: Assay Of Rf and Photoproductsmentioning

confidence: 99%

Effect of phosphate buffer on the complexation and photochemical interaction of riboflavin and caffeine in aqueous solution: A kinetic study

Sheraz

Kazi

Ahmed

et al. 2014

Journal of Photochemistry and Photobiology A: Chemistry

Self Cite

View full text Add to dashboard Cite

a b s t r a c tA study of the photodegradation of 5 × 10 −5 M riboflavin (RF) in 0.2-1.0 M phosphate buffer in the presence and absence of 2.50 × 10 −4 M caffeine at pH 6.0-8.0 has been carried out. RF in phosphate buffer is photodegraded simultaneously by normal photolysis (photoreduction) and photoaddition reactions giving rise to lumichrome (LC) and cyclodehydroriboflavin (CDRF) as the main final products, respectively. RF and its photoproducts, formylmethylflavin (FMF), lumiflavin (LF), LC and CDRF in degraded solution have been determined by a specific multicomponent spectrophotometric method with an accuracy of ±5%. The apparent first-order rate constants for the photodegradation of RF and for the formation of LC and CDRF are 5.47-15.05 × 10 −3 min −1 , 1.06-8.30 × 10 −3 min −1 and 4.31-8.05 × 10 −3 min −1 , respectively. An increase in phosphate concentration leads to an increase in the rate of formation of CDRF and alters the photodegradation of RF in favor of the photoaddition reaction. This photoaddition reaction is further enhanced in the presence of caffeine which results in a further decrease of the fluorescence of RF in phosphate buffer. Caffeine may facilitate the photoaddition reaction by suppression of the photoreduction pathway of RF.

show abstract

Stability‐indicating spectrofluorimetric method for the assay of riboflavin and photoproducts: Kinetic applications

et al. 2018

Self Cite

View full text Add to dashboard Cite

A stability-indicating spectrofluorimetric method has been developed for the simultaneous assay of riboflavin (RF) and photoproducts, formylmethylflavin (FMF), lumichrome (LC) and lumiflavin (LF) in aqueous solution. The method is based on the extraction of LC formed in acid solution and LC and LF formed in alkaline solution with chloroform at pH 2.0 and their assay by fluorescence measurements at 478 and 530 nm, respectively. The aqueous phase, on readjustment of the pH to 6.5, is used to extract FMF with chloroform and its assay is carried out at 530 nm. The aqueous phase is then used for the assay of RF at 530 nm. The proposed method gives more accurate results for the assay of RF compared to those of the United States Pharmacopeia (USP) spectrofluorimetric method which does not take into account the presence of RF photoproducts having similar fluorescence characteristics. The proposed method along with the USP method has been applied to the study of the kinetics of photolysis of RF, assay of stored commercial vitamin preparations and their radiated samples. The results show that the USP method does not distinguish between the fluorescence of RF and its photoproducts, and, therefore, gives erroneous results with about 11% excess in the quantity of the vitamin compared to that of the proposed method. This is due to the interference of the fluorescence of photoproducts in the assay of RF. The method has been validated for various analytical parameters according to the guideline of the International Council for Harmonization (ICH).

show abstract

Multicomponent spectrophotometric assay of riboflavine and photoproducts

Cited by 51 publications

References 39 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

Effect of phosphate buffer on the complexation and photochemical interaction of riboflavin and caffeine in aqueous solution: A kinetic study

Stability‐indicating spectrofluorimetric method for the assay of riboflavin and photoproducts: Kinetic applications

Contact Info

Product

Resources

About