SURFACE ACTIVITY OF ACETOGENINS WITH MONOMOLECULAR FILMS AT THE AIR-WATER INTERFACE

Acetogenins are natural products known for their antiparasitic and antitumoral activity. Nonetheless, its microscopic mechanism of action is still unknown: the compounds can act directly on cell membranes or by penetrating the membrane, affecting intracellular structures. This makes the study of acetogenins with cellular membrane models, such as Langmuir monolayers, interesting. These structures are monolayers oriented at the air-water interface, and it is possible to employ films of lipids to mimic cell membrane structures and study their interaction with bioactive molecules. In this work, we investigated the surface interaction of unsaturated acetogenin with Langmuir films formed by dipalmitoylphosphatidylcholine (DPPC). We characterized the film with surface pressure-area isotherms, cycles of compression-decompression, tensiometric stability, and Brewster Angle Microscopy (BAM). By introducing the bioactive compound into the DPPC monolayer, we observed that the surface pressure-area isotherms are shifted to higher molecular areas in low surface pressures (0-10 mN/m) and lower molecular areas in higher surface pressures (10-54 mN/m). This indicates the condensation of the DPPC monolayer by the drug at the surface pressure of 30 mN/m, which corresponds to the lateral pressure of cell membranes. In addition, we also noted that the presence of acetogenin increased the compressibility of the lipidic film in areas of low molecular density. Thus, we can conclude that acetogenin affected the thermodynamical and rheological properties of DPPC monolayers, which may be crucial to further developing these compounds in possible therapeutic applications, such as drug-delivery systems with liposomes.