Study on the inclusion compounds of eugenol with α-, β-, γ- and heptakis (2,6-di-O-methyl)-β-cyclodextrins

Several host-guest inclusion compounds of eugenol as a guest molecule and cyclodextrins (alpha-,beta-,gamma-CD) and heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DM beta-CD) as hosts were investigated in the solid state and in aqueous solution. The one-to-one solid inclusion compounds of eugenol and beta-CD or gamma-CD were prepared, but those of eugenol with alpha- or DM beta-CD were not obtained under the same condition. However, the UV-visible absorption spectroscopy data indicated that the liquid guest could form a 1:1 inclusion compound with all four hosts respectively in aqueous solution. The two solid inclusion compounds were characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR). The association constants (K), calculated from the modified Benesi-Hidebrand equation, of eugenol with alpha-, beta-, gamma- and DM beta-CD is 4.95x10(4), 3.96x10(5), 1.47x10(5) and 9.33x10(4) mol(-1) dm(3), respectively.