Ultrasound-assisted preparation of 'Ready-to-use' extracts from Radix Paeoniae Rubra with natural deep eutectic solvents and neuroprotectivity evaluation of the extracts against cerebral ischemic/ reperfusion injury.

Natural deep eutectic solvent (NaDES) is widely applied in the extraction of nutrients from natural resources as a greener alternative for fossil solvent. In the present work, 27 different NaDESs were screened for the extraction of paeoniflorin (PF) and galloyl paeoniflorin (GPF) from Radix Paeoniae Rubra (RPR). After screening and extraction parameter optimization, the extraction yields of PF and GPF reached up to 182.8 mg/g and 77.4 mg/g with the selected NaDES, ChCl-Sor. Furthermore, the antioxidant activity in vitro and neuroprotectivity in vivo of the 'ready-to-use' extracts were evaluated comprehensively. Especially in vivo, the cerebral ischemic/ reperfusion injury model was established in rats and the protective effects of the RPR extracts were determined. The results not only proved that NaDES is a valuable green extraction media, but also indicated the safety and potential pharmaceutical application of NaDES based 'ready-to-use' extracts from medical plants.