[Simultaneous determination and optimization of extraction process of catalpol and acteoside from rehmanniae radix].

To establish a method for simultaneously quantification of the Catalpol and Acteoside from Rehmanniae Radix and optimize the extraction process from Rehmanniae Radix by response surface methodology (RSM) using central composite design (CCD). The effect of ethanol concentration and the solvent-material ratio of the extraction were investigated on the overall extraction efficiency. Design Expert was used for regression analysis and determination coefficient of the regression equation. A good linear relationship was obtained from 0.047 - 3.00 microg and 0.016 - 1.00 microg for Catalpol and Acteoside, respectively. The optimal condition of extraction process was as follows: raw material was extracted with 19.3 mL/g solvent-material ratio of 38.0% ethanol. The R-Squared of binomial fitting of the complex model was 0.7498 (P < 0.05). The experimental values were accordance with values obtained from model prediction. The accuracy and precision of the developed HPLC protocol is adequate for simultaneous quantification of Catalpol and Acteoside in Rehmanniae Radix. The optimized extraction condition could be obtained by RSM using CCD.