Nano-encapsulation of thyme essential oil in chitosan-Arabic gum system: evaluation of its antioxidant and antimicrobial properties

In this study, nano-capsules based on chitosan (CS) and Arabic gum (AG) involving thyme essential oil (TEO), as an active ingredient, were prepared using the emulsion method. The nano-capsules were characterized by their encapsulation efficiency (EE), morphologies, particle size distributions, zeta potential and release (RE). The obtained results showed that nano-capsules produced using a relative ratio of CS:AG (1.5%:8.5%) clearly showed the highest encapsulation efficiency (77.67%) and zeta potential value (+ 43.17 mV). In vitro release study demonstrated a slow release for the samples with larger CS ratio. In addition, scanning electron microscopy (SEM) images showed that nano-capsules sizes were over the range 385.2-756.1 nm with a rough surface shape for all samples. Moreover, quantitative values of antioxidant activity of free TEO and nano-encapsulated TEO were studied using the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The essential oil (EO) was investigated for its antibacterial activity against common Grampositive and Gram-negative pathogenic microorganisms including Staphylococcus aureus and Escherichia coli by disk diffusion and dilution (MIC) methods. Our results accounted for higher antioxidant and antibacterial activities of encapsulated TEO compared to those of free TEO. Finally, the CS:AG ratio of 1.5%:8.5% was found to be suitable wall material for TEO encapsulation.