Objective: To determine equilibrium solubility and apparent oil/water partition coefficient of artesunate. Method: Equilibrium solubility of artesunate in water

different organic solvents and some mixed solvent systems were determined by HPLC

chromatographic conditions were as follows:Diamonsil C18(2) column (4.6 mm×250 mm

5 μm)

mobile phase of acetonitrile-phosphate buffer (60:40)

flow rate 1.0 mL·min-1

detection wavelength at 210 nm

column temperature 30℃.Oil/water partition coefficient of artesunate in n-octanol-water/phosphate buffer solution system was established by shake-flask method. Result: Equilibrium solubility of artesunate in water and other organic solvents(chloroform

acetone and absolute ethyl alcohol) was (0.36±0.016)

(598.74±13.11)

(284.63±7.96)

(186.03±8.27) g·L-1 at 32.0℃.Oil/water partition coefficient of artesunate in n-octanol-water system was (249.03±3.76) with logPapp=(2.40±0.006 5). Conclusion: Artesunate had strong fat-soluble

pH value had a greater impact for its equilibrium solubility and apparent oil/water partition coefficient.Equilibrium solubility of artesunate increased when increasing pH value within 5.50-7.43

apparent oil/water partition coefficient of artesunate decreased when pH value increased

but logPapp remained>2.0

indicating that artesunate had strong membrane permeability in in vitro and in vivo circumstances.