Synthesis and Characterization of β-Cyclodextrin-Essential Oil Inclusion Complexes for Tick Repellent Development

Abstract

Essential oils (EOs) are used in several pest management applications. Due to their volatility, EOs may experience bioactivity reduction, thus requiring protection to extend their properties. In the present study, we investigated the inclusion complex formation (IC) of β-cyclodextrin (β-CD) with selected EOs with known tick repellent activity using two co-precipitation methods. ICs were characterized by evaluating EO mass concentration and inclusion efficiency (% IE) and other instrumental methods. Co-precipitation method 2 yielded the highest EO mass concentration (88 ± 6 μg/mg β-CD) for the 1:1 molar ratio geranium Egyptian EO IC. The EO volatile release over time from the ICs was investigated by headspace SPME/GC-MS analysis. ICs were also tested in tick repellency bioassays. ICs reported significant tick repellent activity, with lemongrass IC performing best overall. Method 1 showed the best combination of high mass concentration EO, controlled volatile release, and tick repellency with lemongrass EO. The results demonstrated that β-CD had selectively encapsulated different EOs. Moreover, the formation of ICs may improve EO tick repellent properties protecting the active ingredients and providing a better, long-lasting repellent action. These findings will allow the development of more effective naturally derived repellent products to protect individuals from tick bites and prevent tick-borne illnesses.