Alcohol-Free Delivery System Carrying Thyme Essential Oil Nanoparticles Formulated via Microemulsion Technique
Abstract:In the current investigation, the essential oil of red wild thyme (Thymus serpyllum) was formulated as nanoparticles in alcohol-free micoemulsion using biocompatible surfactant. The solubilization behavior of the oil was investigated and described on ternary and pseudo-ternary phase diagrams. A ternary microemulsion system using thyme essential oil (TEO), water, and Tween 20 can be fully diluted at two different dilution lines without the need of solubilization enhancer like short chain alcohols. The ratios of surfactant/TEO at these lines were 9:1 and 8:2 wt/wt, respectively, and the corresponding particle sizes of TEO microemulsion were 7.9 nm and 10.2 nm, respectively. At line L9,1, the microemulsion could be fully diluted without loss of the microstructure. However, at line L8,2 the system passed through a liquid crystalline phase at water content higher than 30.0% and less than 60.0%, then returned to its isotropic and dilutable nature again at the higher water contents. Re-formulation of TEO in microemulsion systems containing propylene glycol (PG) as co-solvent increased the isotropic microemulsion region without showing new dilution lines. The chemical composition of TEO was revealed and correlated with its solubilization behavior. Linalool (36.88%) and borneol (18.39%) were the major oil constituents and are thought to have co-surfactant-like activity that enhanced the extent of microemulsion formation of TEO. On the other hand, carvacrol content was surprisingly low (6.08%) with poor microemulsion forming ability. The results of this investigation could be useful for developing alcohol-free, water dilutable delivery system carrying TEO nanoparticles for application in food flavoring and preservation, personal hygiene products and pharmaceutical formulations.
Document Type: Research Article
Publication date: December 1, 2011
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