Effect of eugenol acetylation on encapsulation, controlled release, and antimicrobial properties of alginate films incorporating lignin microparticles

Abstract In this work, lignin microparticles were synthesized using the antisolvent method for the encapsulation of eugenol and acetyl eugenol. Acetyl eugenol was synthesized by esterification and characterized by spectroscopic techniques (¹H NMR, ¹³C NMR, and two-dimensional NMR). Lignin microparticles exhibited spherical morphology with an average size of approximately 2 µm. The obtained microparticles were subsequently incorporated into sodium alginate films aimed at developing materials with antimicrobial activity. The encapsulation efficiency (EE) increased with the initial drug loading, and the higher EE of acetyl eugenol was attributed to its lower polarity and higher affinity for the hydrophobic domains of lignin. In vitro drug release studies revealed different profiles: acetyl eugenol exhibited a faster release rate, whereas eugenol presented a slower release because hydrogen-bond interactions with lignin delayed diffusion. Alginate films exhibited a homogeneous surface and excellent thermal stability, and the incorporation of lignin microparticles into the film was confirmed by FTIR and microscopy studies. Microbiological assays demonstrated that the composite materials maintained the antimicrobial activity compared to the free active compounds, with pronounced bactericidal effect against Staphylococcus aureus ATCC 29213. These results highlight the potential of lignin microparticles as controlled-release platforms for the fabrication of active materials for food packaging applications.