RESUMO
<p><b>OBJECTIVE</b>To investigate the physicochemical constants such as equilibrium solubility and apparent partition coefficients (Papp), and study the effects of temperature, pH value and antioxidants on the stability of breviscapine solution.</p><p><b>METHOD</b>The equilibrium solubility of breviscapine in various medium and the Papp of breviscapine under different pH conditions were determinated by RP-HPLC, and the effects of temperature, pH value and antioxidants on the stability of solution were investigated by taking change rates of drug content in 10 h as detection index.</p><p><b>RESULT</b>The equilibrium solubility of breviscapine in saline, distilled water, pH 7.0 PBS, pH 7.5 PBS, Ringer's fluid, methanol and ethanol were (20.68 +/- 1.12), (79.35 +/- 0.68), (7954.62 +/- 34.90), (18,708.17 +/- 253.05), (3670.40 +/- 27.64), (210.71 +/- 0.74), (184.34 +/- 1.47) mg x L(-1) respectively; while in pH value 3.0, 4.0, 5.0, 6.5, 7.0 solution, the Papp were 5.362, 0.542, 0.371, 0.328 and 0.143 respectively. The stability of breviscapine in the Ringer's fluid was the worst and the stability was significantly decreased with the increase of temperature and pH value and it could be improved by EDTA-2Na.</p><p><b>CONCLUSION</b>The established HPLC assay was accurate and convenient. The Papp of breviscapine is decreased by increased the pH value, while in the aqueous solution the equilibrium solubility of breviscapine increase with the pH in crese. EDTA-2Na can be used as an antioxidant of breviscapine solution.</p>