An efficient approach for the extraction of glycoproteins from American ginseng by natural deep eutectic solvent

Glycoproteins have not been reported in the previous studies of American ginseng. This study focuses on developing an efficient method for the extraction of glycoproteins from American ginseng (GAG). Three choline chloride (ChCl)-based natural deep eutectic solvents (NADES) and three extraction techniques including microwave-, ultrasound-, and heating and stirring-assisted extraction were evaluated in the study. Extraction processes were optimized via response surface methodology. The results indicated that all three ChCl-based NADES were effective for the extraction of GAG, and the microwave-assisted choline chloride:malic acid (ChCl:MalA) showed the highest efficiency. Maximum yield of GAG (19.91 %) was achieved using microwave-assisted ChCl:MalA extraction under the following conditions: ChCl:MalA molar ratio of 1:2, water content of 80 %, liquid/solid ratio of 20 mL/g, microwave time of 26 min, microwave power of 62 W, and extraction temperature of 110 °C. The microwave-assisted ChCl:MalA increased GAG yield by 47 % while reducing processing time by 87 % compared to conventional extraction. Structural characterization of GAG showed that different extraction methods had a significant effect on its structure, and the GAG extracted by microwave-assisted ChCl:MalA had a moderate molecular weight, a narrow molecular weight distribution, a high percentage of glucose composition, typical glycoprotein structural features, and a rough surface morphology. In addition, the glycoproteins extracted via microwave-assisted ChCl:MalA demonstrated superior in vitro hepatoprotective activity. In conclusion, microwave-assisted ChCl:MalA would be an efficient method for GAG.