Stabilizing effect of citrate buffer on the photolysis of riboflavin in aqueous solution

Results in Pharma Sciences
Iqbal AhmadMohammad Aminuddin

Abstract

In the present investigation the photolysis of riboflavin (RF) in the presence of citrate species at pH 4.0-7.0 has been studied. A specific multicomponent spectrophotometric method has been used to assay RF in the presence of photoproducts during the reactions. The overall first-order rate constants (k obs ) for the photolysis of RF range from 0.42 to 1.08×10(-2) min(-1) in the region. The values of k obs have been found to decrease with an increase in citrate concentration indicating an inhibitory effect of these species on the rate of reaction. The second-order rate constants for the interaction of RF with total citrate species causing inhibition range from 1.79 to 5.65×10(-3) M(-1) min(-1) at pH 4.0-7.0. The log k-pH profiles for the reactions at 0.2-1.0 M citrate concentration show a gradual decrease in k obs and the value at 1.0 M is more than half compared to that of k 0, i.e., in the absence of buffer, at pH 5.0. Divalent citrate ions cause a decrease in RF fluorescence due to the quenching of the excited singlet state resulting in a decrease in the rate of reaction and consequently leading to the stabilization of RF solutions. The greater quenching of fluorescence at pH 4.0 compared to that of 7.0 is in accordance with...Continue Reading

Citations

Feb 3, 2012·International Journal of Cosmetic Science·I AhmadF H M Vaid
Sep 24, 2014·Beilstein Journal of Organic Chemistry·Muhammad Ali SherazIqbal Ahmad
Oct 11, 2014·Chemistry : a European Journal·Małgorzata Insińska-Rak, Marek Sikorski
Oct 2, 2015·Drug Delivery and Translational Research·Chase S LinsleyBenjamin M Wu
Jul 20, 2017·Applied Biochemistry and Biotechnology·Maryam Sadat NabaviniaKhalil Abnous

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