Evaluation of the effects in cellular membrane models of antitrypanosomal poly-thymolformaldehyde (PTF) using Langmuir monolayers.

The polymerization of bioactive compounds may be interesting because the supramolecular structures formed can boost biological action on microorganism membranes. In the present work, poly-thymolformaldehyde (PTF) activity, prepared by condensation of thymol and formaldehyde, was evaluated against trypomastigote forms of Trypanosoma cruzi and related with the physicochemical changes provided by the incorporation of the compound in protozoan cell membrane models. PTF exhibited an EC50 value of 23.4 µg/mL and no toxicity against mammalian cells (CC50 > 200 µg/mL). To understand the molecular action of PTF as an antiprotozoal candidate, this compound was incorporated in Langmuir monolayers of dipalmitoylphosphatidylglycerol (DPPG) as a model for parasite cell membranes. PTF shifted DPPG surface pressure-area isotherms to higher areas, indicating its incorporation in the lipid films. Additionally, it changed the thermodynamic, compressional, structural, and morphological properties of the floating monolayers, decreasing the collapse pressure, reducing the surface elasticity, and segregating molecules at the interface, forming domains with different reflectivities. Infrared spectroscopy showed that the lipid films with PTF presented an increased rate of gauche/all-trans conformers for the methylene groups from the acyl chains, indicating molecular disorder. Therefore, these results show that PTF alters the physicochemical properties of DPPG monolayers as a model for protozoa cell membranes, which can enhance the comprehension of the parasitic action of PTF against T. cruzi.

The interaction of eugenol with cell membrane models at the air-water interface is modulated by the lipid monolayer composition.

Eugenol, a natural phenylpropanoid derivative with possible action in biological surfaces as microbicide, anesthetic and antioxidant, was incorporated in lipid monolayers of selected lipids at the air-water interface, representing cell membrane models. Interaction of eugenol with the lipids dipalmitoylphosphatidylcholine (DPPC), dioctadecyldimethylammonium bromide (DODAB), and dipalmitoylphosphatidylserine (DPPS) could be inferred by means of surface pressure-area isotherms and Polarization-Modulation Reflection-Absorption Spectroscopy. The interaction showed different effects on the different lipids. A higher monolayer expansion was observed for DPPS and DODAB, while more significant effects on the polar groups of the lipids were observed for DPPS and DPPC. These results pointed to the fact that the interaction of eugenol with lipid monolayers at the air-water interface is modulated by the lipid composition, which may be important to comprehend at the molecular level the interaction of this drug with biological surfaces.