Complexation of Eugenol (EG), as Main Component of Clove Oil and as Pure Compound, with β- and HP-β-CDs

Eugenol, both in its pure form (EG) and included in essential clove oil (CO) was successfully solubilized in aqueous solution by forming inclusion complexes with β-cyclodextrins (β-CDs) and its modified hydroxypropyl-β-CDs (HP-β-CDs). To investigate the molecular association between β-CDs/HP-β-CDs with pure EG and essential CO, phase solubility studies were undertaken. Essential CO formed insoluble complexes with β-CDs, but not with HP-β-CDs. The work clearly demonstrates complexes formation follow an order higher than 1:1 when high essential CO and β-CDs concentrations were used, however it was 1:1 in the case of essential CO-HP-β-CDs complexes. When pure EG was studied the results indicated that EG could form 1:1 inclusion complexes with β-CDs and HP-β-CDs. Based on the studies, the Kc values for pure EG were 4555 ± 225 M and 10,633 ± 614 M for β-CDs and HP-β-CDs, respectively, and 2005 ± 199 M for essential CO-HP-β-CDs. These finding indicate that CDs are suitable for encapsulating EG.