Abstract
Serum albumin carries several ligands in the circulation. Previous studies demonstrated that certain flavonoid aglycones and their sulfate metabolites can influence the albumin binding of Site I ligand drugs. To get a deeper insight, the effects of chrysin, quercetin, luteolin, myricetin, and their sulfate derivatives on the albumin binding of warfarin (Site I) and biliverdin (heme site) were examined. Ultracentrifugation experiments were carried out using human serum albumin (HSA), bovine serum albumin (BSA), human serum, and fetal bovine serum (FBS). In addition, fluorescence spectroscopic and modeling studies (warfarin-HSA) as well as circular dichroism-based measurements (biliverdin-HSA) were also performed. Chrysin-7-O-sulfate and quercetin-3'-O-sulfate considerably displaced warfarin from HSA, while warfarin-BSA interaction was strongly disturbed by luteolin-3'-O-sulfate and quercetin-3'-O-sulfate. Quercetin-3'-O-sulfate, luteolin-3'-O-sulfate, and chrysin-7-O-sulfate caused the marked displacement of biliverdin from HSA. In contrast, quercetin-3'-O-sulfate and luteolin-3'-O-sulfate significantly increased the stability of biliverdin-BSA complex. Flavonoid sulfates did not affect the free fraction of warfarin and biliverdin in spiked human serum samples. However, in the presence of 10% FBS (as in cell culture media), high flavonoid levels elevated the free fraction of warfarin, while certain flavonoids considerably decreased the free fraction of biliverdin. Our results demonstrate the complex modulation of warfarin-albumin and biliverdin-albumin interactions by flavonoids. It likely does not influence the albumin binding of Site I and heme site ligands in the human circulation, but flavonoids can strongly affect ligand-BSA interactions in cell culture media.