Spectroscopic and Computational Insights into Different Binding with Bovine Serum Albumin and Esterase-Like Activity Tuning: Echinatin versus Licochalcone B

The interactions of two chalcones, echinatin (ECN) and licochalcone B (LCB), differing by a single B ring phenolic–OH, with bovine serum albumin (BSA) and their modulation of BSA esterase-like activity were investigated spectroscopically and via molecular docking under physiological conditions. UV–vis absorption, fluorescence, and competitive displacement assays revealed both ligands form ground-state complexes with BSA at Sudlow Site I. Thermodynamics showed spontaneous, exothermic binding driven by hydrogen bonds and van der Waals forces. Raman and docking indicated ECN binds via its A ring and carbonyl, whereas LCB binds via its B ring and carbonyl. This subtle structural difference yields distinct binding modes, underlying their differing modulation of BSA esterase-like activity, with LCB being a stronger enhancer. These findings reveal how a single hydroxyl difference tunes albumin recognition and activity regulation, shedding light on their pharmacological and pharmacokinetic divergence while guiding the design of licorice-derived chalcones.