Quercetin, Catechin, and Diosmin as Modulators of Haloperidol-HSA Interactions: A Biophysical and Computational Study

Potential interactions of haloperidol with food ingredients such as flavonoids may be of great importance both for understanding the pharmacokinetic interactions of xenobiotics with human serum albumin and for clinical practice itself. In this study, the effect of the flavonoids quercetin, catechin, and diosmin on the interaction of haloperidol and human serum albumin was examined. These flavonoids are very common in foods of plant origin. Haloperidol is a typical antipsychotic that has a pronounced binding affinity for human serum albumin. Fluorescence spectroscopy, molecular docking analysis, and molecular dynamics simulations were used for these tests. Previous studies have shown that all test substances bind to the same binding site on human serum albumin (Sudlow site I, Subdomain IIA). Fluorescence spectroscopy revealed that the tested flavonoids reduce the value of the haloperidol binding constant to human serum albumin (from 4.45 × 10³ in the binary system to 3.75 × 10², 5.40 × 10² and 6.24 × 10² in the ternary systems, respectively), due to competition for the same binding site. Experimental results were confirmed by molecular docking analysis and molecular dynamics simulations.