Study on the supramolecular interaction of curcumin and β-cyclodextrin by spectrophotometry and its analytical application

The supramolecular interaction of curcumin and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied and discussed based on the variations of pK(a), absorption intensity, and infrared spectrograms. The results show that beta-CD reacts with curcumin to form a 2:1 host-guest complex with an apparent formation constant of 5.53 x 10(5) mol(-2) L-2. Based on the enhancement of the absorbance of curcumin produced through complex formation, a spectrophotometric method for the determination of curcurnin in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and curcurnin concentration was obtained in the range of 0-15,mug/mL, with a correlation coefficient (r) of 0.9991. The detection limit was 0.076 mug/mL. The proposed method was used to determine the curcurnin in curry and mustard with satisfactory results.