Study on interaction between apigenin and human serum albumin by spectroscopy and molecular modeling

Apigenin (Ap) is one of the most common dietary flavonoids, and possesses extensive bioactivities. In our work, interaction of Ap and human serum albumin (HSA) had been investigated systematically by fluorescence spectroscopic, circular dichroism (CD), UV–vis absorption spectroscopic and molecular modeling. The results indicated that binding of Ap to HSA caused strong fluorescence quenching of HSA through static quenching mechanism, hydrophobic and electrostatic interaction are the predominant forces in the Ap–HSA complex, and the process of Ap binding HSA was droved by enthalpy (ΔH = −17.497 kJ mol−1) and entropy (ΔS = 37.04 J mol−1). The results from synchronous fluorescence showed that microenvironment around tyrosine (Tyr) had a slight trend (about blueshift of 1 nm) of polarity decreasing. The formation of the complex had not changed the secondary structure of HSA by CD. The binding distance r between donor (HSA) and acceptor (Ap) is 3.21 nm according to the theory of Förster resonance energy transfer. By method of molecular modeling, Ap was located to the entrance of site I by hydrophobic and electrostatic forces, which matched exactly the corresponding experimental results.