Abstract:

The association constant and inclusion proportion for the inclusion complex of volatile oil of Cymbopogon citratus (VOC) with cyclodextrins (β-CD, DM-β-CD, and HP-β-CD) were determined in the range of 20 － 50 ℃ by ultraviolet spectrometry. The effect of temperature on K value and other parameters ΔG, ΔH and ΔS had also been discussed. Good linear relationships indicated that the structures of the inclusion complex were 1:1. The association constant (Ka) of the complexes had been obtained, and the order that the capability associated with VOC was HP- β-CD >DM- β-CD >β-CD. The inclusive process was an exthermic and enthalpy-driven process accompanied with a negative entropic contribution, and the reciprocity of hydrophobic interaction and van der Waals force plays an importance role in the process.

Key words: Cymbopogon citratus volatile oil, β-cyclodextrin derivatives, ultraviolet spectrometry, association constants, thermodynamics