Abstract: Natural deep eutectic solvent (NADES) was used to extract steviosides from Stevia rebaudiana as an efficient, green and environmentally friendly new method. Compared with traditional solvent water, the optimal NADES formula was selected to extract S. rebaudiana dry leaves by measuring the concentration of stevioside and rebaudioside A, two main components in steviosides. The extraction conditions of NADES extracting steviosides were optimized by Box-Behnken design from response surface methodology. The best NADES formula for steviosides extraction was selected: 1,2-propanediol:glycerol:water=8:1:1 (v/v/v), the extraction concentration of stevioside was 2.59 mg∙mL^-1 (16.40% higher than water), and the extraction concentration of rebaudioside A was 1.06 mg∙mL^-1 (12.62% higher than water). The NADES extraction conditions were optimized by response surface methodology: extraction time was 90 min, extraction temperature was 60°C, ultrasonic power was 80 J∙s^-1, the predicted extraction concentration of stevioside was 3.49 mg∙mL^-1 and the concentration of rebaudioside A was 1.43 mg∙mL^-1, which was close to the experimental verification value (the concentration of stevioside is 3.48 mg∙mL^-1, the concentration of rebaudioside A is 1.42 mg∙mL^-1). Under the best condition, the extraction of stevioside was 34.36% higher than the initial condition, and the extraction of rebaudioside A was 33.96% higher than the initial condition. NADES is environmentally friendly and has higher extraction efficiency than traditional solvents. It can be used for the green extraction of steviosides from S. rebaudiana. At the same time, it provides a promising prospect for the green extraction of natural products from other bulk economic plants.

Key words: NADES, Stevia rebaudiana, stevioside, rebaudioside A, green extraction