Natural deep eutectic solvents as new green solvents to extract anthraquinones from Rheum palmatum L

Y C Wu; P Wu; Y B Li; T C Liu; L Zhang; Y H Zhou

doi:10.1039/c7ra13581e

Natural deep eutectic solvents as new green solvents to extract anthraquinones from Rheum palmatum L

RSC Adv. 2018 Apr 20;8(27):15069-15077. doi: 10.1039/c7ra13581e. eCollection 2018 Apr 18.

Authors

Y C Wu¹, P Wu¹, Y B Li^{1

2}, T C Liu¹, L Zhang¹, Y H Zhou³

Affiliations

¹ College of Science, Sichuan Agricultural University Ya'an Sichuan 625014 China zhang8434@sina.com.
² School of Tourism and Resource Environment, Qiannan Normal College for Nationalities Guizhou 558000 P. R. China.
³ Triticeae Research Institute, Sichuan Agricultural University Chengdu Sichuan 611130 P. R. China.

Abstract

Natural deep eutectic solvents (NADESs) are efficient in extracting natural products. However, traditional organic solvents are toxic in the extraction of anthraquinones from Rheum palmatum L. To solve this problem, we applied natural deep eutectic solvent ultrasound-assisted extraction in this study for the extraction of total anthraquinones from R. palmatum L. Principal component analysis revealed that the selected NADES which consisted of lactic acid, glucose and water (LGH), was highly efficient in extracting anthraquinones from R. palmatum L. The ratio of lactic acid/glucose and the addition of water in LGH were investigated via a single-factor experiment. With a lactic acid/glucose ratio of 5 : 1 (mol/mol), and 10% of water (v/v), LGH had a high extraction yield to anthraquinones. Optimized by response surface methodology (RSM), the optimized extraction conditions of extraction time, extraction temperature and solvent-to-solid ratio of 1.5 h, 82 °C and 26 mL g^-1, respectively. Under optimum conditions, the extraction yields of aloe-emodin, rhein, emodin, chrysophanol, physcion and total anthraquinones were 2.60 ± 0.01, 5.78 ± 0.02, 2.21 ± 0.02, 5.87 ± 0.02, 8.81 ± 0.01 and 25.27 ± 0.07 mg g^-1, respectively. The enrichment and separation of five anthraquinones in LGH extraction solution were efficiently achieved using DM130 macroporous resin, with purities of 90.98%, 96.67%, 92.37%, 95.80% and 91.61% as indicated by HPLC, and recovery yields of 84.08%, 79.51%, 84.96%, 81.83% and 78.35%, respectively. LGH was environmentally friendly and highly efficient in extracting anthraquinones from R. palmatum L., and NADESs showed potential for the extraction of effective components from natural products.