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Abstract
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The aim of this study was to explore the efficiency of ephedrine binding to human serum albumin (HSA)
as a protein model using spectroscopic, electrochemical, and molecular docking methods. A reduction in
UV absorbance at 280 nm of HSA was attributed to the interaction between ephedrine and HSA. The
apparent binding constant (Kapp) values at different temperatures were about 104 M1, which showed
high affinity of ephedrine for HSA. The calculated negative enthalpy change (DH) and entropy change
(DS) values suggested that the binding process was mainly driven by van der Waals force and hydrogen
bonds. The negative value of free energy change (DG) indicated that the interaction process was spontaneous.
The results of cyclic voltammetry (CV) further confirmed the high affinity of ephedrine for HSA
with an association constant of 2.73 ± 0.17 104 M1 at room temperature. Furthermore, molecular
docking results revealed that ephedrine bound to site I in subdomain IIA via 2 hydrogen bonds with
Phenylalanine 211 (Phe211) and Alanine 215 (Ala215) of HSA, and that Arginine 218 (Arg 218), Lysine
199 (Lys 199), and Serine 202 (Ser202) residues became involved in electrostatic interactions with ephedrine.
Also, Leucine 198 (Leu198), Phe211, Tryptophan 214 (Trp214), Leu238, and Histidine 242 (His242)
residues were responsible for the stability of the complex via hydrophobic interactions. Attenuated total
reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was used to investigate the conformational
changes of HSA during the interaction of ephedrine and HSA.
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