Ultrasound-assisted natural deep eutectic solvents (NaDES) extraction of gentiopicroside, isovitexin, and isogentisin from Gentiana asclepiadea L. biowaste

Through the application of green and sustainable practices, this study introduces an innovative approach for the valorization of Gentiana asclepiadea L. herbal dust based on natural deep eutectic solvents (NaDES) coupled with ultrasound-assisted extraction (UAE). NaDES composed of choline chloride and 1,2-propanediol (ChCl:PG) was selected as the most effective for the simultaneous extraction of gentiopicroside, isovitexin, and isogentisin, monitored as markers of three major classes of secondary metabolites in Gentiana L. species. Response surface methodology based on the Box-Behnken design was employed for extraction modeling and optimization. Extraction yields under optimized NaDES-UAE conditions (80 °C, 39.97 min, and 28.30% w/w water in NaDES) were 50.28 mg/g DW for gentiopicroside, 4.17 mg/g DW for isovitexin, and 0.51 mg/g DW for isogentisin. Molecular dynamics results revealed that the extensive hydrogen-bonding network and electrostatic interactions were the most significant contributors to the extraction capacity of the ChCl:PG NaDES mixture. Overall, the high-efficiency and eco-friendly method developed in this study offers a powerful way to use G. asclepiadea biowaste as a promising source of valuable compounds for pharmaceutical formulations.