Objective: To investigate effects of different factors on the content of paeoniflorin in water extract and concentrated solution of Shujing Fangtong prescription

to optimize process conditions by analyzing thermal degradation kinetics of paeoniflorin. Method: HPLC was employed to determine the content of paeoniflorin with mobile phase of 0.05% potassium dihydrogen phosphate-acetonitrile (85:15) and detection wavelength at 230 nm.Effects of different factors on the content of paeoniflorin in water extract and concentrated solution of Shujing Fangtong capsules. Result: Main factors affecting the content of paeoniflorin were heating temperature and time in preparation process of Shujing Fangtong capsules.Thermal degradation reaction of paeoniflorin in water extract accorded with thermodynamic first-order reaction equation

thermal degradation rate constant (K) increased significantly with increasing of temperature;its thermal degradation reaction accorded with thermodynamic first-order reaction equation of lgC=-0.002t+1.345(r=0.990 4) in concentrated solution at 80 ℃

K was 4.606×10-3

validity was 22.88 h

half-life was 150.46 h. Conclusion: High temperature and long time heating should avoid in preparation process of Shujing Fangtong capsules

vacuum concentration method and vacuum drying method should be adopted to reduce degradation rate of paeoniflorin.