Thermodynamic and kinetic analyses of curcumin and bovine serum albumin binding

•Native and unfolded bovine serum albumin (BSA) and curcumin (CUR) formed a complex.•Thermodynamic binding parameters depended on the analytical technique used.•Fluorescence indicated an enthalpic and entropic driven native BSA/curcumin complex.•Microcalorimetry showed an entropic driven native BSA/curcumin binding process.•BSA, especially in native state, increased the curcumin photodegradation stability.

Bovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 105 L·mol−1 by fluorescence and microcalorimetric, and 103 and 104 L·mol−1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH○F = −8.67 kJ·mol−1), while microcalorimetry showed an entropic driven binding process (ΔH○cal = 29.11 kJ·mol−1). For the unfolded BSA/curcumin complex, it was found thatp ΔH○F = −16.12 kJ·mol−1 and ΔH○cal = −42.63 kJ·mol−1. BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding.