Study on the interaction of the hyperoside and HSA in VC and VC -free environment by spectroscopic and molecular docking techniques.

The interaction between hyperoside and human serum albumin was studied in VC and VC -free environment using UV-vis absorption, fluorescence, circular dichroism spectra and molecular docking techniques under simulated physiological conditions. The two environments had different influences on the secondary structure of HSA. The α-helix content was slightly increased from 50% to 51% in VC environment and, increased from 50% to 55% in VC -free environment. The thermodynamic parameters were ΔH° = -30.7 KJ⋅mol-1 and ΔS° = -23.4 mol-1 ⋅K-1 in VC environment and ΔH° = -25.4 KJ⋅mol-1 and ΔS° = -11.4 J⋅mol-1 ⋅K-1 in VC -free environment respectively. Through the thermodynamics parameters, hydrophobic force played a dominant role in the whole environment. The binding constants were both calculated to be 7.25 × 105 mol⋅L-1 and 9.76 × 105 mol⋅L-1 at 298 K and they declined with the raise of temperature. The two binding distances were 2.6 nm and 2.5 nm respectively at 298 K, indicating that fluorescence energy transfer occurred. The UV-vis spectra indicated the fluorescence quenching of HSA-hyperoside complex was a static quenching process. Hyperoside could spontaneously bind to HSA at site Ι (subdomain IIA). Molecular docking elucidated the way of binding basically through hydrophobic and van der Waals force interactions. Moreover, molecular docking showed that the VC environment can influence the binding of HSA and hyperoside by more H-binding and less hydrophobic forces.