Dissociation Constants and Solubilities of Daidzein and Genistein in Different Solvents

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• 作者：Guanjun Nan ; Jiao Shi ; Yanru Huang ; Jing Sun ; Jianhua Lv ; Guangde Yang ; Yiping Li
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2014
• 出版时间：April 10, 2014
• 年：2014
• 卷：59
• 期：4
• 页码：1304-1311
• 全文大小：279K
• 年卷期：v.59,no.4(April 10, 2014)
• ISSN：1520-5134

文摘

The dissociation constants (pK_a) of daidzein and genistein were determined at 298.2 K by ultraviolet (UV) spectroscopy method. The pK_a1 and pK_a2 values of daidzein are 7.51 卤 0.07 and 9.47 卤 0.14 and ones of genistein are 7.25 卤 0.84 and 9.53 卤 0.15, respectively. The solubilities of daidzein and genistein in water, methanol, ethyl ethanoate, propanone, trichloromethane, and hexane have been measured using UV spectrophotometric method from (288.2 to 328.2) K at atmospheric pressure. The solubilities of daidzein and genistein in all solvents increase with an increase in temperature. The solubility of daidzein in the six solvents was in the order propanone > methanol > ethyl ethanoate > hexane > trichloromethane > water, whereas the solubility order of genistein was propanone > ethyl ethanoate > methanol > hexane > trichloromethane > water. In comparing the solubility of genistein with that of daidzein, the 5-hydroxyl group of genistein causes a significantly higher solubility in methanol and ethyl ethanoate, a little higher solubility in trichloromethane (exception 328.2 K), an approximately equivalent solubility in water, and a slightly lower solubility in propanone. The measured solubility data were correlated with a modified Apelblat equation, 位h model, and ideal model. From solubility of daidzein and genistein in these six solvents, the dissolution enthalpy, entropy, and change of the free Gibbs energy were evaluated using the van鈥檛 Hoff equation.