Probing the interaction of polyphenols with lipid bilayers by solid-state NMR spectroscopy

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• Polyphenols are bioactive compounds with diverse health benefits.
• Their mechanisms of action are not fully understood, but membrane interactions are a recent focus.
• Understanding polyphenol-membrane interactions is key to elucidating their biological activities.

Purpose of the Study:

• To investigate the interaction between lipid bilayers and three distinct polyphenols: (-)-epigallocatechin gallate (EGCg), a proanthocyanidin trimer (cat₃), and a hydrolyzable tannin (PGG).
• To determine how polyphenol characteristics like polarity, size, and hydroxyl group arrangement influence their binding to lipid membranes.
• To assess the impact of these polyphenols on lipid bilayer dynamics using solid-state NMR.

Main Methods:

• Incorporation of EGCg, cat₃, and PGG into ²H-labeled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) multilamellar vesicles (MLVs).
• Analysis using ³¹P and ²H solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Calculation of order parameters to assess perturbations in the lipid bilayer's headgroup and acyl chain regions.

Main Results:

• Polyphenol addition decreased the chemical shift anisotropy (CSA) width in ³¹P NMR spectra, indicating changes in the headgroup region.
• PGG caused a significant reduction in CSA width, while cat₃ had a minimal effect.
• ²H NMR revealed that PGG substantially reduced the quadrupolar splitting, indicating greater perturbation of the hydrophobic acyl chain region compared to cat₃.

Conclusions:

• Polyphenol polarity is a critical factor governing their interaction with lipid membranes.
• PGG, a more polar polyphenol, significantly perturbs the lipid bilayer structure.
• These findings suggest that polyphenol-membrane interactions, influenced by polarity, may underlie their broad biological activities.