RESUMEN
Objective: To investigate the isomerization law of aescins A, B, C, and D under different conditions and optimize the isomerization process. Methods: Using the conversion of aescin C and D, and the content of impurity as index, single factor experiment was applied to evaluate the effect trends of isomerization from three parameters including pH value, reaction temperature and time. Then, central composite design-response surface method was used to estimate the relationship between the dependent and independent variables and to validate the optimal conditions. Results: According to the single factor experiment, the effect trends of three parameters on conversion of aescins C and D were analogous, and the isomerization happened under the conditions as follows: pH value of 5.0-10.0, reaction temperature of 45-85℃, and reaction time of 0.25-8 h. Based on the central composite design, the optimal conditions were predicted as follows: pH value was 6.9, reaction temperature was 54℃ and reaction time was 7.4 h. Under such conditions, the experimental values showed on significant difference from the predicted values. Conclusion: The isomerization of aescins A, B, C, and D could show a certain law under different conditions, and the optimal isomerization process is stable and available, which could provide a scientific basis of regulating the proportion of aescins A, B, C, and D during industrial production.