Poly(thioether-ester) nanoparticles entrapping clove oil for antioxidant activity improvement

Abstract

Poly(thioether-ester) was synthesized from dianhydro-d-glucityl diundec-10-enoate (DGU), a fully renewable diester diene monomer, and a dithiol, and employed to nanoencapsulate clove oil, a great source of eugenol, aiming to improve its antioxidant activity. Nanoparticles were obtained by miniemulsion polymerization with clove oil varying from 0 to 25% (w/w of DGU). Spherical and stable nanoparticles were obtained with particle size between 192 and 284 nm and high encapsulation efficiency (~98%). Results of FT-IR and DSC also confirmed the incorporation of clove oil into nanoparticles, with a gradual reduction in the melting point from 66 °C to 50 °C with the addition of clove oil. In addition, monomer conversion and polymer molar masses decreased with the increase of the amount of clove oil, probably due to the occurrence of reactions between thiyl groups and the double bond of eugenol. These results suggest that part of the incorporated clove oil is chemically bound to the polymer chain forming particles with bound/loaded clove oil. Poly(thioether-ester) nanoparticles loaded with 6% of clove oil exhibited an increase in antioxidant activity of ~26% for β-carotene/ linoleic acid assay and a reduction of 66% on EC₅₀ for 2,2-diphenyl-1-picryl hydrazyl assay.

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