Factors affecting the entrapment efficiency of β-cyclodextrins and their effects on the formation of inclusion complexes containing essential oils

Abstract β-cyclodextrins (β-CDs) are macrocyclic molecules made from starch capable of entrapping hydrophobic compounds in an aqueous solution. This study aimed to determine, for the first time, the main factors that affect the entrapment efficiency (EE) of β-CDs using the essential oils (EOs) of palmarosa and star anise as guest models of hydrophobic compounds. The results show that the EE of β-CDs was greatly affected by the β-CD intramolecular water content, EO/β-CD adding order, EO type, EO concentration, drying process type, and extraction solvent type. Consequently, the EE of β-CDs varied from 1.05 to 63.7% and from 9.84 to 70.7% for palmarosa and star anise EOs, respectively, depending on the changes made to the above listed factors. The novel inclusion complexes were thermally and physico-chemically characterized, and their release kinetics measured over different environmental conditions to relate structural information to both entrapment and controlled release. This study demonstrates the importance of the aforementioned factors in obtaining the adequate EE values and provides guidance in optimizing the EE of β-CDs.