Objective: The present study was performed to investigate competitive interaction between arenobufagin and verapamil hydrochloride with serum albumin.
Methods: Equilibrium dialysis and high-performance liquid chromatography were used to analyze the binding rates of the two medicines to serum protein. The interactions based on bovine serum albumin (BSA) and human serum albumin (HSA) were investigated by using spectrofluorimetry. The interaction mode of arenobufagin and verapamil hydrochloride binding to serum proteins was simulated by molecular docking.
Results: The rate of arenobufagin (0.1μg/mL) binding to bovine serum was (61.1±0.2)%. Verapamil hydrochloride (0.025 to 0.1μg/mL) significantly reduced the bovine serum binding rate of arenobufagin, from (60.2±3.7)% to (36.9±3.4)%. However, arenobufagin at the tested doses had no marked effects on the binding rate of verapamil hydrochloride. Furthermore, the verapamil hydrochloride had an active effect on the arenobufagin-induced fluorescence quenching of BSA and HSA. The molecular docking results showed that verapamil hydrochloride and arenobufagin binded to HSA at site I. Molecular interaction energy of verapamil hydrochloride binding to site I was stronger than that of arenobufagin.
Conclusion: Verapamil hydrochloride reduces the binding of arenobufagin to bovine serum. The mechanism may be a competitive interaction of arenobufagin and verapamil hydrochloride at site I on HSA.