[Solubility peak and dielectric requirement of Buyang Huanwu docoction]

To study the solubility peak and dielectric requirement of the Buyang Huanwu docoction materials, and provide theoretical and experimental foundation for selecting extraction solvent for extracting traditional Chinese drugs (TCD).

11 types of solvents were employed as single or complex solvent systems, whose solubility parameter and dielectric constant were from 14.11 to 47.86, dielectric requirement from 1 to 80 respectively, to lixiviate Buyang Huanwu decoction (5 g per samples) in nearly saturate volume as V0 for materials at 25 degrees C. The apparent solubilities of extracts were determined and calculated out according to the section of determination of extract in the appendix of 'Chinese Pharmacopoeia'.

The saturate solvent V0 for materials powder were 0.21, 0.31, 0.49, 0.36, 0.77, 0.93, 0.86, 0.92, 1.08, 1.00, 1.14 mL x g(-1), respectively. The apparent solubility of Buyang Huanwu docoction for each solvent system were 114.0, 101.3, 73.40, 109.4, 210.7, 295.0, 501.4, 437.0, 355.6, 423.1, 210.6 g x mL(-1), respectively, among which the max apparent solubility, illustrated as solubility peak, was carried out by methanol-water (68: 32) with 47.5 corresponding to the Buyang Huanwu docoction dielectric requirement.

The apparent solubilities of (TCD) and their formula are controlled by dielectric constant of extraction solvent, and are in accordance with stable dielectric requirement.