Objective: To study the stability and degradation kinetics of Ketoprofen-Paeonol conjugate (Ket-Pae).
Method: RP-HPLC method was used to determine the solubility and partition coefficient of Ket-Pae. Stability test was carried out to investigate the factors affecting Ket-Pae. The kinetic studies of Ket-Pae degradation were conducted in different pH buffer solutions and 80% rat plasma at 37 degrees C.
Result: Ket-Pae showed significant degradation phenomenon at high temperature. The solubility of Ket-Pae was decreased about 200 to 300 times compared with parent drugs in water while the lnP increased about 4 times. The degradation curve displayed a V-shape, and kept maximum stability at week acidic (pH 5.0, t(1/2) = 11.4 d). Ket-Pae degraded quickly with very short half life of 1.3 min in plasma, therefore easily released ketoprofen and paeonol.
Conclusion: The lipophilicity of Ket-Pae is increased, its stability is affected by temperature and pH value.