title: Aqueous solubility and stability enhancement of astilbin through complexation with cyclodextrins.
abstract: The complexation of astilbin with α-, β-, and γ-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 α-CD < γ-CD < β-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 β-CD microcapsules prepared by the freeze-drying method was enhanced by 122.1-fold, and its dissolution profile was improved.
authors.affiliation: Jiangxi Key Laboratory of Natural Product and Functional Food, College of Food Science and Engineering, Jiangxi Agricultural University, Nanchang 330045, China. zhqf619@126.com
authors.forename: Qing-Feng
authors.initials: QF
authors.lastname: Zhang
authors.forename: Hai-Chun
authors.initials: HC
authors.lastname: Nie
authors.forename: Xin-Cheng
authors.initials: XC
authors.lastname: Shangguang
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Yin
authors.forename: Guo-Dong
authors.initials: GD
authors.lastname: Zheng
authors.forename: Ji-Guang
authors.initials: JG
authors.lastname: Chen
mesh_terms: D002942:Circular Dichroism; D003505:Cyclodextrins / Q000737:chemistry*; D004355:Drug Stability; D044948:Flavonols / Q000737:chemistry*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014867:Water
chemical_list: D003505:Cyclodextrins; D044948:Flavonols; D014867:Water; C099069:astilbin