Interaction of the antiprotozoal compound in cell membrane models using Langmuir monolayers

Natural compounds extracted from plants can display biological action, including antimicrobial and tumorigenic. Many of these biological actions involve the interaction of lipidic surfaces, including cellular membranes. A helpful way to model these membranes is employing Langmuir films, a monomolecular structure formed by insoluble amphiphiles at the air-water interface. In this work, we isolated the compound 15-senecioyloxy kaurenoic acid methyl ester that has potential antiprotozoal properties and incorporated it in Langmuir monolayers of 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC), a known lipid for mimic erythrocytes membranes. For that, we co-spread the compound and the lipid on the air-water interface and characterized the assembled monolayer with tensiometric measurements, morphological (Brewster Angle Microscopy), electric (surface potential), and rheological measurements (oscillating barriers). Surface pressure-area isotherms showed that the antiprotozoal compound condensed the DPPC monolayer, decreased the surface potential, stabilized the previously compressed monolayers up to 30 mN/m, and caused the formation of interfacial aggregates. Compression-decompression curves presented hysteresis for the mixed monolayer. Rheological measurements showed that the compound decreased the viscoelastic modulus for the DPPC monolayer, making the film more fluid. The pure and mixed lipid monolayer did not present a significative viscous contribution, being the monolayer essentially elastic. These results show that this antiparasitic compound interacts with cell membrane models, which is essential to understand the mechanism of action at the molecular level in detail.

This work was supported by FAPESP (2022/03736-7) and CNPq.