Binding of Epimedium Flavonoids to Human Serum Albumin: Insights from Spectroscopic and Molecular Docking Studies

Epimedin A (EA), epimedin B (EB), and epimedin C (EC), major bioactive flavonoids in Epimedium Herba, have diverse pharmacological activities; however, their interactions with human serum albumin (HSA) remain unclear.

This study aimed to investigate the binding mechanisms of EA, EB, and EC to HSA.

Multispectroscopic techniques, including UV-vis, fluorescence, and synchronous fluorescence spectroscopy, as well as molecular docking and dynamics simulations, were employed under simulated physiological conditions. Fluorescence spectra were recorded at 298, 303, and 310 K, and molecular docking was performed with HSA (PDB ID: 1BKE).

All three flavonoids quenched the intrinsic fluorescence of HSA via static quenching, forming 1:1 complexes with binding constants greater than 10⁴ L·mol^-1 (EB > EA > EC at 298 K). Thermodynamic analysis indicated spontaneous binding driven by hydrogen bonds and van der Waals forces. Synchronous fluorescence showed no significant microenvironmental changes around Trp and Tyr residues. Molecular docking and dynamics simulations suggested ligand-dependent differences in the preferred binding regions of HSA.

These findings provide preliminary in vitro evidence for the binding of epimedin flavonoids to HSA and may inform future pharmacokinetic investigations.