posted on 2024-03-15, 07:29authored byCheng Yang, Haijun Yan, Qianhe Huang, Wenge Yang, Yonghong Hu
Esculetin is derived from the leaves of lemons of Rutaceae
and
the bark of bittersweet ash, belladonna, mandala, and Rehmannia plants.
In this research, the solubility of esculetin in ten solvents such
as ethyl acetate, isobutyl alcohol, water, methanol, acetonitrile, n-propyl alcohol, isopropyl alcohol, n-butanol,
ethanol, and acetone was determined by utilizing static equilibrium-high
performance liquid chromatography (HPLC) under standard atmospheric
pressure conditions and temperatures in the range of 273.15 to 318.15
K. Among the above ten pure solvents, water
displayed the least solubility, while methanol exhibited the highest
solubility. At the same temperature (T = 273.15 ∼
318.15 K), the solubility of esculetin increased with the increase
of the molar ratio of soluble solvents. Similarly, when the temperature
increases (T = 273.15 ∼ 318.15 K), the solubility
of the three binary solvents increases under the condition of a constant
molar ratio. The above results suggest that the main factor affecting
the solubility of esculetin in the solvent may be the polarization/bipolarity
of the solvent. The experimental data was fitted by five thermodynamic
models (the Buchowski–Ksiazaczak λh model,
the Modified Apelblat model, the Jouyban–Acree model, the SUN
model, and the CNIBS/R-K model), and the relative average deviation
and root-mean-square deviation of the data were calculated, which
proved that the correlation of the solubility data and the five models
was relatively good. XRD and DSC were used to detect the crystal form
and stability of esculetin during the experiment.