Thermodynamic study on the effects of beta-cyclodextrin inclusion with berberine.
The fluorescence enhancement of berberine (Berb) as a result of complex with beta-cyclodextrin (beta-CD) is investigated. The association constants of alpha-CD and beta-CD with Berb are 60 and 137 M(-1) at 20 degrees C in pH 7.20 aqueous solution. Effects of temperature on the forming inclusion complexes of beta-CD with Berb have been examined through using fluorescence titration. Enthalpy and entropy values calculated from fluorescence data are -33.7 kJ mol(-1) and 74.3 J x mol(-1) K(-1) respectively. It was found that the dielectric constant of beta-CD cavity is about 24 in a rough analogy with absolute alcohol. These results suggest that the extrusion of 'high energy water' molecules from the cavity of beta-CD and hydrophobic interaction upon the inclusion complex formation are the main forces of the inclusion reaction. Effect of pH on the association of beta-CD with Berb was also studied. Mechanism of the inclusion of beta-CD with Berb is further studied by absorption and NMR measurements. Results show that beta-CD forms a 1:1 inclusion complex with Berb.
Yu
Jun-Sheng
JS
Department of Chemistry, Institute of Analytical Science, Nanjing University, People's Republic of China. ndchemyu@public1.ptt.js.cn
Wei
Fang-Di
FD
Gao
Wei
W
Zhao
Chang-Chun
CC
D001599:Berberine / Q000737:chemistry*; D003505:Cyclodextrins / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D013057:Spectrum Analysis; D013696:Temperature; D013816:Thermodynamics; D047392:beta-Cyclodextrins
D003505:Cyclodextrins; D047392:beta-Cyclodextrins; D001599:Berberine; C031215:betadex