Binding of Tolperisone Hydrochloride with Human Serum Albumin: Effects on the Conformation, Thermodynamics, and Activity of HSA

Tolperisone hydrochloride (TH) has muscle relaxant activity and has been widely used for several years in clinical practice to treat pathologically high skeletal muscle tone (spasticity) and related pains. The current study was designed to explore the binding efficacy of TH with human serum albumin (HSA) using multispectrscopic, calorimetric approach, FRET, esterase-like activity, and a molecular docking method. A reduction in fluorescence emission at 340 nm of HSA was attributed to fluorescence quenching by TH via a static quenching type. Binding constants (Kb) were evaluated at different temperatures, and obtained Kb values were ∼104 M–1, which demonstrated moderately strong affinity of TH for HSA. A calculated negative ΔG° value indicated spontaneous binding of TH to HSA. Far-UV CD spectroscopy revealed that the α-helix content was increased after TH binding. The binding distance between donor and acceptor was calculated to be 2.11 nm based on Forster’s resonance energy transfer theory. ITC results rev...