The use of response surface methodology to optimize the ultrasound-assisted extraction of five anthraquinones from Rheum palmatum L.

In this paper, ultrasound-assisted extraction (UAE) was applied to the extraction of anthraquinones (aloe-emodin, rhein, emodin, chrysophanol and physcion) from Rheum palmatum L. The five anthraquinones were quantified and analyzed by high performance liquid chromatography coupled with UV detection (HPLC-UV). The extraction solvent, extraction temperature and extraction time parameters, the three main factors for UAE, were optimized with response surface methodology (RSM) to obtain the highest extraction efficiency. The optimal conditions were the use of 84% methanol as solvent, an extraction time of 33 min and an extraction temperature of 67°C. Under these optimal conditions, the experimental values agreed closely with the predicted values. The analysis of variance indicated a high goodness of model fit and the success of RSM method for optimizing anthraquinones extraction in Rheum palmatum L.