Yu Jun-Sheng, Wei Fang-Di, Gao Wei, Zhao Chang-Chun
Department of Chemistry, Institute of Analytical Science, Nanjing University, People's Republic of China.
Spectrochim Acta A Mol Biomol Spectrosc. 2002 Jan 15;58(2):249-56. doi: 10.1016/s1386-1425(01)00536-4.
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.
研究了黄连素（Berb）与β-环糊精（β-CD）形成复合物后荧光增强的情况。在20℃、pH 7.20的水溶液中，α-环糊精和β-环糊精与黄连素的缔合常数分别为60和137 M⁻¹。通过荧光滴定研究了温度对β-环糊精与黄连素形成包合物的影响。根据荧光数据计算得到的焓值和熵值分别为-33.7 kJ·mol⁻¹和74.3 J·mol⁻¹·K⁻¹。发现β-环糊精空腔的介电常数与无水乙醇大致类似，约为24。这些结果表明，从β-环糊精空腔中挤出“高能水分子”以及包合物形成时的疏水相互作用是包合反应的主要驱动力。还研究了pH对β-环糊精与黄连素缔合的影响。通过吸收光谱和核磁共振测量进一步研究了β-环糊精与黄连素包合的机理。结果表明，β-环糊精与黄连素形成了1:1的包合物。
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