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[摘要]：The complexation of astilbin with alpha-, beta-, and gamma-cyclodextrin (CD) was studied by phase solubility test and UV-vis spectral titration. Complexation with CDs gradually decreased the absorbance of astilbin at 291 nm and obviously increased its water solubility. The formation constant (K-a) between astilbin and the three CDs was calculated. The stability of astilbin complexes increased in the order alpha-CD < gamma-CD < beta-CD, attributed to the CDs' cavity size. Temperature studies showed that the K-a value decreased along with the rise of temperature. The negative values of enthalpy and entropy during complexation indicated that the complexation process was enthalpy-controlled. In alkaline medium isomerization and decomposition of astilbin were found; however, the addition of CDs significantly improved its stability through complexation. The solubility of astilbin in beta-CD microcapsules prepared by the freeze-drying method was enhanced by 122.1-fold, and its dissolution profile was improved. |
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