Study on the interaction of hyperoside and human serum albumin in V C and V C ‐free environments by spectroscopic and molecular docking techniques

The interaction between hyperoside and human serum albumin was studied in vitamin C (VC ) and VC -free environments using ultraviolet (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 human serum albumin (HSA). The α-helix content was slightly increased from 50% to 51% in the VC environment and increased from 50% to 55% in the VC -free environment. The thermodynamic parameters were ΔH° = -30.7 kJ⋅mol-1 and ΔS° = -23.4 mol-1 ⋅K-1 in the VC environment and ΔH° = -25.4 kJ⋅mol-1 and ΔS° = -11.4 J⋅mol-1 ⋅K-1 in the VC -free environment. Through thermodynamics parameters, hydrophobic force played a dominant role in the whole environment. The binding constants were calculated to be 7.25 × 105 mol⋅L-1 and 9.76 × 105 mol⋅L-1 at 298 K and they declined with the rise in 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 that fluorescence quenching of the HSA-hyperoside complex was a static quenching process. Hyperoside could spontaneously bind to HSA at site I (subdomain IIA). Molecular docking elucidated the way to binding basically through hydrophobic and van der Waals force interactions. Moreover, molecular docking showed that the VC environment could influence binding of HSA and hyperoside by more H-binding and less hydrophobic forces.