Investigation of the interaction of aurantio-obtusin with human serum albumin by spectroscopic and molecular docking methods

The interaction between human serum albumin (HSA) and aurantio-obtusin was investigated by spectroscopic techniques combined with molecular docking. The Stern-Volmer quenching constants (K-SV) decreased from 8.56x10(5)M(-1) to 5.13x10(5)M(-1) with a rise in temperatures from 289 to 310K, indicating that aurantio-obtusin produced a static quenching of the intrinsic fluorescence of HSA. Time-resolved fluorescence studies proved again that the static quenching mechanism was involved in the interaction. The sign and magnitude of the enthalpy change as well as the entropy change suggested involvement of hydrogen bonding and hydrophobic interaction in aurantio-obtusin-HSA complex formation. Aurantio-obtusin binding to HSA produced significant alterations in secondary structures of HSA, as revealed from the time-resolved fluorescence, Fourier transform infrared (FT-IR) spectroscopy, three-dimensional (3D) fluorescence and circular dichroism (CD) spectral results. Molecular docking study and site marker competitive experiment confirmed aurantio-obtusin bound to HSA at site I (subdomain IIA).