Optimization of forsythoside extraction from Forsythia suspensa by Box-Behnken design

The optimum conditions for the extraction of forsythoside from Forsythia suspensa were determined using response surface methodology. A Box-Behnken design was performed to evaluate the effects of ratio of water to raw material, extraction temperature and time on yield of forsythoside. Statistical analysis of results showed that, the linear and quadric terms of these three variables had significant effects, and evident interaction existing between extraction temperature and ratio of water to raw material was found to contribute to the response at a significant level. Furthermore, Box-Behnken design used for the analysis of treatment combinations gave a second-order polynomial regression model, which was in good agreement with experimental results, with R-2=0.9809 (P<0.05). The optimal conditions for the yield of forsythoside obtained using response surface methodology and canonical analysis were ratio of water to raw material of 21.38, extraction temperature of 72.06 degrees C and extraction time of 2.56 h. Under the optimum conditions, the experimental value of 6.62 +/- 0.35% was well in close agreement with value predicted by the model, thus indicating suitability of the model employed and the success of response surface methodology in optimizing the extraction conditions.