Extraction of polysaccharides from Paeoniae Radix Rubra using natural deep eutectic solvents: process optimization, characterization, and neuroprotective effect against MPP+-induced SH-SY5Y cell injury

Extraction of Paeoniae Radix Rubra polysaccharide (PRRP). • Firstly, the PRRP was extracted by Natural Deep Eutectic Solvent (NADES). • Firstly, the PRRP was extracted by ChCl-CA (1.5, 3:2) with 40% ( w / w ) water. • AGREEprep and BAGI confirmed ChCl-CA’s greenness: polysaccharide yield >9%, solvent recovery >80%. • Firstly, the neuroprotective activity of PRRP in Parkinson's disease was evaluated. Firstly, natural deep eutectic solvents (NADES) were used to extract polysaccharides from Paeoniae Radix Rubra (PRR). Using polysaccharide yield and neuroprotective cell activity as evaluation criteria, a solvent composed of 40% ( w / w ) water, choline chloride (ChCl), and citric acid (CA) was selected as the optimal solvent. It exhibited low viscosity, high surface tension, moderate polarity, and strong acidity. Fourier-transform infrared (FT-IR) spectra of the ChCl-CA confirmed the formation of hydrogen bonding. Response surface methodology (RSM) optimized conditions: molar ratio: 1.5 (3:2), extraction temperature: 60 °C, extraction duration: 64 min, solvent-solid ratio: 36 mL·g −1 , the polysaccharide yield reached 16.74%, which was 1.89 times that of the hot water extraction, and the SH-SY5Y cell activity in the methyl-4-phenylpyridinium (MPP + )-induced PD model was 86.86%. The obtained PRR polysaccharides (PRRP) were further characterized, with protein content of 5.23% and uronic acid content of 19.09%. PRRP was mainly composed of arabinose, glucose, and galacturonic acid. Its molecular weights are 73.381, 11.475, and 3.539 kDa. PRRP was characterized via Ultraviolet-Visible (UV–Vis) and FT-IR spectroscopy, confirming typical polysaccharide structures. After 6 cycles, the polysaccharide yield of recycled NADES decreased from 16.26% to 9.22% in the final extraction, a 43.30% decrease. Two classical green evaluation models quantitatively confirmed the process's environmental friendliness. In addition, in vitro experiments showed that PRRP could increase dopamine (DA) and tyrosine hydroxylase (TH) levels, reduce lactate dehydrogenase (LDH) release, and decrease α -synuclein ( α -Syn) accumulation. This study highlights the efficiency of ChCl-CA as a green extractant and reveals the neuroprotective effect of PRRP. Download: Download high-res image (162KB) Download: Download full-size image Graphical abstract created in BioRender. com