Inhibitory Effect of Condensed Tannins from Banana Pulp on Cholesterol Esterase and Mechanisms of Interaction

In the present study, the inhibitory effect of condensed tannins (CTs) on cholesterol esterase (CEase) was studied. The underlying mechanisms were evaluated by reaction kinetics, turbidity and particle size analyses, multispectroscopy methods, thermodynamics, and computer molecular simulations. CTs showed potent CEase inhibitory activity with an IC₅₀ value of 64.19 μg/mL, and the CEase activity decreased with increasing CT content in a mixed-competitive manner, which was verified by molecular docking simulations. Fluorescence and UV–vis measurements revealed that complexes were formed from CEase and CTs by noncovalent interaction. Isothermal titration calorimetry indicated that the interaction between CEase and CTs occurred through hydrogen bonding and hydrophobic interactions. Circular dichroism analysis suggested that CTs inhibited the activity of CEase by altering the secondary structure of CEase. The inhibition of CTs on CEase in the gastrointestinal tract might be one mechanism for its cholesterol-lowering effect.