Abstract

Ugni molinae Turcz, also known as "Murtilla", is a plant that grows in the south of Chile. Infusions of their leaves have long been used in traditional native herbal medicine. The chemical composition of the leaves indicates the presence of polyphenols, which have antioxidant properties. In order to evaluate the mechanisms of their antioxidant properties and the toxicity of the aqueous extracts of leaves, the extracts were induced to interact with human red cells, their isolated unsealed membranes (IUM) and large unilamellar vesicles (LUV) of dimyristoylphosphatidyltidylcholine (DMPC), representative of phospholipid classes located in the outer monolayer of the erythrocyte membrane. Scanning electron microscopy (SEM) observations indicated that the extracts achieved a significant alteration in the shape of the erythrocytes as they changed their discoid shape to echinocytes. According to the bilayer couple hypothesis, the shape change indicates that the polyphenols were located in the outer moiety of the red cell membrane. This conclusion was confirmed by the fluorescence experiments performed in IUM and DMPC LUV. In fact, the extracts produced slight initial increases followed by sharp decreases at higher concentrations in the anisotropy and general polarization parameters. These results imply that the extracts induced structural perturbations in the acyl chain and polar group packing arrangements of the erythrocyte IUM and DMPC LUV lipid bilayers: first ordering and afterwards disordering them as the extract concentration increased. © 2006 Elsevier Ltd. All rights reserved.