Characterizing the interaction between methyl ferulate and human serum albumin by saturation transfer difference NMR

Methyl ferulate (MF) is an alkyl ferulate ester that widely exists in edible plants and has application value in the food and medicine industries. Thus, its effect on biological macromolecules should be considered. In this study, we exploit saturation transfer difference NMR (STD-NMR) to characterize the interaction of all protons of MF with human serum albumin (HSA) at the molecular level. STD-NMR and K _a (1.298 × 10³ M^-1) revealed that protons H1-6 and H8 bound to HSA with a medium affinity. Binding epitope mapping further showed that the aromatic ring played a key role in the HSA-MF interaction. STD-NMR site-marker-displacement experiments and circular dichroism spectroscopy revealed that MF prefered to bind to site II of HSA without changing the basic skeleton of HSA. Computer simulations confirmed these experimental results. Overall, this work elucidates the molecular level interaction of MF with HSA and provides new insights into the possibility of the potential applications of MF in the food and medicine industries.