Green tea extract-biomembrane interaction study: The role of its two major components, (-)-epigallocatechin gallate and (-)-epigallocatechin.

The interaction of antioxidants with biological membranes is closely related with their efficacy to inhibit the lipid peroxidation, the cause of several pathologies including cancer, neurodegenerative and cardiovascular disorders. Despite being pointed as a promising antioxidant agent by some authors, the anti-lipid peroxidation of green tea extract (GTE) has not aroused consensus among the scientific community. Since the interaction of drugs with biological membranes plays a key role on their therapeutic activity, this study aims to evaluate the interaction of GTE with liposomes as in vitro biomembrane models composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine phospholipids in the absence and presence of cholesterol (CHOL) (15 mol%). The affinity of GTE and its main components (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) to the lipid bilayer, their membrane location as well as their effect on the membrane fluidity was investigated by diverse biophysical techniques. Derivative spectrophotometry results proved that GTE has high affinity to the membrane by establishing hydrophobic interactions with the non-polar region of phospholipids and electrostatic interactions with the polar phospholipid heads. Fluorescence and dynamic light scattering data confirm that GTE is located in both hydrophobic and hydrophilic regions of the lipid membrane, therefore affecting the structure of the biomembrane by increasing its fluidity. However, the increased stiffness and organization of the lipid bilayer caused by CHOL significantly affected the interaction of GTE with the membrane. Moreover, the obtained findings suggest a direct contribution of EGCG and EGC on the GTE-membrane interaction.