The effect of albumin in photostabilization of riboflavin: A kinetic study

This investigation involves a study of the photochemical interaction of riboflavin (RF) and bovine serum albumin (BSA) in aqueous solution and the evaluation of this effect on the photostabilization of RF. RF solution (5 x 10(-5) M) were irradiated with visible light in the presence of BSA (4.0-6.0 x 10(-5) M) at pH 7.4 (0.005 M, phosphate buffer saline) and the apparent first-order rate constants for the photolysis of RF were found to be in the range of 3.92-9.26 x 10(-3) min(-1).The rate of RF photolysis is inhibited with an increase in the concentration of BSA. The second-order rate constant for the photochemical interaction of RF and BSA at pH 7.4 is 1.22 M-1 min(-1). There is a gradual loss of RF fluorescence with an increase in BSA concentration due to the formation of a non-fluorescent complex between the two molecules. The value of Stern-Volmer quenching constant has been determined as 2.673 x 10(3) M-1. A two-component spectrometric method with correction for irrelevant absorption caused by BSA components has been used to determine RF and its photoproduct, lumichrome (LC), in photolyzed solutions. The mode of photochemical interaction of RF and BSA has been discussed.