Effects of synthetic food colorants on the interaction between norfloxacin and bovine serum albumin by fluorescence spectroscopy

The effects of synthetic food colorants like tartrazine, sunset yellow, and erythrosine on the binding reaction between norfloxacin and bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. Results showed that food colorants bound to BSA by van der Waals force and hydrogen bonding formation and norfloxacin by electrostatic interaction. In addition, marker competitive experiments suggested that the primary binding site for both norfloxacin and food colorants was located at subdomain IIA of BSA (site I). The presence of food colorants could alter the binding constant and distance between BSA and norfloxacin. The effects of colorants were dependent on their concentrations and binding affinity to BSA. The interaction could result in the change of the free, biologically active fraction of norfloxacin in blood.