Enantioselective Binding of Proton Pump Inhibitors to Alpha1-Acid Glycoprotein and
Human Serum Albumin—A Chromatographic, Spectroscopic, and In Silico Study
Gyógyszerészet, farmakogenomika, gyógyszerkutatás és tervezés, gyógyszeres kezelés
The enantioselective binding of three proton pump inhibitors (PPIs)—omeprazole, rabeprazole,
and lansoprazole—to two key plasma proteins, α1-acid glycoprotein (AGP) and human
serum albumin (HSA), was characterized. The interactions between PPI enantiomers and
proteins were investigated using a multifaceted analytical approach, including high-performance
liquid chromatography (HPLC), fluorescence and UV spectroscopy, as well as in silico
molecular docking. HPLC analysis demonstrated that all three PPIs exhibited enantioseparation
on an AGP-based chiral stationary phase, suggesting stereoselective binding to AGP,
while only lansoprazole showed enantioselective binding on the HSA-based column. Quantitatively,
the S-enantiomers of omeprazole and rabeprazole showed higher binding affinity to
AGP, while the R-enantiomer of lansoprazole displayed greater affinity for AGP, with
a reversal in the elution order observed between the two protein-based columns. Protein
binding percentages, calculated via HPLC, were greater than 88% for each enantiomer
across both transport proteins, with all enantiomers displaying higher affinity for
AGP compared to HSA. Thermodynamic analysis indicated that on the HSA, the more common,
enthalpy-controlled enantioseparation was found, while in contrast, on the AGP, entropy-controlled
enantioseparation was observed. The study also identified limitations in using fluorescence
titration due to the high native fluorescence of the compounds, whereas UV titration
was effective for both proteins. The determined logK values were in the range of 4.47–4.83
for AGP and 4.02–4.66 for HSA. Molecular docking supported the experimental findings
by revealing the atomic interactions driving the binding process, with the predicted
enantiomer elution orders aligning with experimental data. The comprehensive use of
these analytical methods provides detailed insights into the enantioselective binding
properties of PPIs, contributing to the understanding of their pharmacokinetic differences
and aiding in the development of more effective therapeutic strategies.