Antimicrobial Activity of Nano-Encapsulated Essential Oils: Comparison to Non-Encapsulated Essential Oils

As fragile active components, essential oils should be encapsulated to solve several problems linked to their use, including toxicity, miscibility in aqueous medium, time-controlled release, formulations or preparations for various industries (pharmaceuticals, cosmetics, textiles, chemicals, food, etc.). Then, the aim of this study is to perform nano-encapsulation of selected essential oils and to compare their antimicrobial activities with the non-encapsulated ones. Essential oils of Thymus leptobotrys, Thymus satureoides, Pelargonium graveolens, Eugenia Caryophyllata and their major component Eugenol were first encapsulated by the nanoprecipitation technique using Eudragit RS 100 as coating polymer. This results in a final stable milky dispersion of essential oils nanocapsules having a final concentration of 4% (v/v). The formed nanoparticles have 110 nm averages in diameter particle size and possess positive zeta potential (approximately 81 mV). Chemical composition of these encapsulated essential oils was investigated by Gas Chromatography-Mass Spectrometry confirming similarities to the non-encapsulated ones. Antimicrobial assays against five bacterial strains, two yeasts and two moulds, confirm that the prepared nanoparticles exhibit, at a comparative concentration of 0.4% (v/v), relatively less antimicrobial activities (both bacteriostatic and fungistatic) than the non-encapsulated EOs. These results lead us to think to numerous applications of such essential oils particularly in the pharmaceutical and cosmetic domains.