Objective: To determine the oil-water partition coefficients of podophyllotoxin at variable pH and to assess the solubilizing effect of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) on podophyllotoxin. Method: The water solubility and oil-water partition coefficient of podophyllotoxin in different pH media were determined using the shake-flask method. The inclusion processes with HP-β-CD were optimized through orthogonal design. The solubilization effect of HP-β-CD on podophyllotoxin was investigated by a phase-solubility method. Result: The solubility of podophyllotoxin in water was 0.09 g ·L-1

while the solubility in octanol was 12.91 g ·L-1. The distribution of podophyllotoxin between water and octanol could be achieved balance in 5min. The oil-water partition coefficient (P) of podophyllotoxin was 179.067

so logP was 2.249.The phase solubility diagram was AL-type

and the inclusion constant (K) was 1 022.65 L ·mol-1. Conclusion: Podophyllotoxin is high lipophilic

and distributes to be balanced rapidly between water and oil. The HP-β-CD has good solubilization effect on podophyllotoxin

which forms stable inclusion complexes with podophyllotoxin.