Effects of different drying methods on the contents of active ingredients of Saposhnikovia divaricata (Turcz.) Schischk and optimization of the drying process by response surface methodology

Abstract Introduction Saposhnikovia divaricata (Turcz.) Schischk is one of the most widely used Chinese herbs worldwide. It has anti‐inflammatory and analgesic properties and hence has a high clinical value. As the moisture level in S. divaricata is high after harvest, it requires drying. Objective We aimed to find a scientific drying method and optimize the drying conditions of the best drying method of S. divaricata using response surface methodology (RSM). Methodology The effects of 4 different drying methods on the contents of prim‐ O ‐glucosylcimifugin, cimifugin, 5‐ O ‐methylvisamminol, and sec‐ O ‐glucosylhamaudol were determined using high‐performance liquid chromatography. Chroma, the rehydration ratio, and active component content were used as indices, and slice thickness, drying temperature, and drying time were used as independent variables to optimize the drying conditions of the optimal drying method of S. divaricata using RSM combined with the Box–Behnken design. Results The results showed that the optimal drying conditions were as follows: slice thickness, 4.00 mm; drying temperature, 60°C; and drying time, 15 h. Conclusion Under optimal drying conditions, the measured values were extremely close to the predicted values. The results of variance analysis showed that the model had a high degree of fit and the drying conditions of S. divaricata were optimized successfully.