Deep eutectic solvents for ginsenoside extraction and inhibition of ginsenoside hydrolysis in Panax notoginseng leaves: methodology and mechanistic insights

Panax notoginseng leaves (PNL) are renowned for rich ginsenoside content. The choice of extraction solvents is critical, as the β -glucosidase in PNL can lead to ginsenoside hydrolysis. Herein, we synthesized 43 deep eutectic solvents (DESs) to simultaneously extract ginsenosides and inhibit the hydrolysis. The various extraction parameters were evaluated using single-factor experiments and optimized by response surface methodology. Our findings identified choline chloride-urea (ChCl-Ure, 1:2 mol/mol) as the most effective solvent under the optimized condition: water content of 29.1 %, solid-to-liquid ratio of 1:50.9, extraction temperature of 50.8 °C, and extraction duration of 59.2 min. Compared to conventional water extraction, the DES method significantly improved extraction efficiency (106.8 mg/g vs. 73.0 mg/g) while dramatically reducing ginsenoside hydrolysis (7.0 % vs. 100.0 %). Although the extraction efficiency and hydrolysis ratio with DES were similar to those of methanol, DES notably minimized chlorophyll extraction (0.1 mg/g vs. 4.7 mg/g). Furthermore, ginsenosides were refined at a high rate (80.3 %) from DES extract using macroporous resins, and the DES was successfully recovered and reused 4 times. Mechanistic studies revealed that the enhanced extraction efficiency of ChCl-Ure DES resulted from its ability to disrupt cell walls, strong electrostatic potential attraction, low binding energy, and effective hydrogen bonding and van der Waals forces with ginsenosides. Molecular dynamics simulations indicated that DES restricted the flexibility of critical amino acids in the β -glucosidase catalytic pocket, enhancing its structural rigidity and reducing its activity. Mainstream greenness assessment metrics and economic evaluation highlighted the environmental and economic benefits of the extraction strategy. Collectively, this eco-friendly method offers significant advantages, including high extraction efficiency, low residual chlorophyll, and effective inhibition of ginsenoside hydrolysis, making it a promising approach for extracting ginsenosides from PNL or Panax leaves.