Simultaneous Extraction of Salidroside and Tyrosol from Rhodiolarosea L. Using Tailor-made Deep Eutectic Solvents

A method for simultaneously extracting the salidroside and tyrosol from Rhodiolarosea L. using deep eutectic solvents (DESs) as the extraction solvents was developed in this work. Firstly, the hydrogen bond donor (HBD), hydrogen bond acceptor (HBA), molar ratio of HBA to HBD, and water content were optimized. The optimal DES for the simultaneous extraction was obtained as ethylene glycol-levulinic acid at the molar ratio of 1 : 1 and water content of mass fraction of 40%, which was recorded as LAEG-40. Then, taking the LAEG-40 as the extraction solvent, the extraction conditions such as extraction method , solid to solvent ratio, extraction temperature and extraction time were further optimized. The optimal conditions were obtained as follows stirring extraction at the solid to solvent ratio of 1 : 12. 5(g/mL) and 60 degrees C for 65 min. Under these conditions, the extraction yields of salidroside and tyrosol reached (18. 1268 +/- 0. 1667) and (1. 5608 +/- 0. 0240) mg/g, respectively. However, under the same conditions, taking water or ethanol as the extraction solvents, the extraction yields of salidroside and tyrosol were (15. 1221 +/- 0. 1342) and (1. 1120 +/- 0. 0389) mg/g, or (16. 3425 +/- 0. 0897) and (1. 1923 +/- 0. 0423) mg/g, respectively. It could be seen that the extraction efficiency of LAEG-40 was obviously higher than those of traditional solvents. The results showed that LAEG-40 was a green and efficient solvent for simultaneous extraction of salidroside and tyrosol, which could be used as a substitute for traditional solvents.