Multicomponent natural deep eutectic solvents: Super solvents for the efficient extraction of steviol glycosides (rebaudioside A) from Stevia rebaudiana

Using biomass to produce valuable chemicals has tremendous economic significance; however, in some cases, it poses environmental challenges due to the use of organic solvents. NAtural Deep Eutectic Solvents (NADESs), a sustainable and bio-based functional liquid medium, can be a greener substitute for organic solvents to extract chemical scaffolds from biomass. Although water is an environmental-friendly solvent, it's challenging to tune its selectivity toward extracting a particular class of molecules from biomass. In contrast, NADESs selectivity toward extracting diverse types of molecules can be easily adjusted by a simple variation of the molar ratios of its components. In the current study, Stevia rebaudiana, a well-known calorie-free sweetener, was targeted to extract steviol glycosides. The quantification results revealed that NADES 50 (lactic acid: glycerol: malic acid: glucose, 1:1:1:1) was most efficient to extract, e.g., 38.24 +/- 2.22 mg/g and 114.58 +/- 5.89 mg/g of rebaudioside A (SG2) and stevioside (SG3), respectively. However, NADES 36 (choline chloride: lactic acid: oxalic acid: glycerol, 2:2:1:1) extracted all targeted analytes (90.69 +/- 3.10 mg/g) along with untargeted compounds. The extraction carried out with the optimized parameters was improved by 33.77% and 24.86% in terms of extraction yields of steviol glycosides by NADES 50 and NADES 36, respectively. The crude steviol glycosides were efficiently separated from the NADESs using HP-20 resin. The extraction efficiency of recovered NADES was 30-36% lower than that of their fresh counterparts. The structure of both NADES i.e., NADES 50 and NADES 36 matrices, was characterized by NMR spectroscopy to confirm their structural arrangement. The current study concluded that multicomponent NADESs have excellent extractability of steviol glycosides from the leaves of S. rebaudiana compared to binary NADESs.

Automated summary

Using natural deep eutectic solvents (NADESs) as greener substitutes for organic solvents, the current study investigated the extraction of steviol glycosides from Stevia rebaudiana. The results showed that NADES 50 (lactic acid: glycerol: malic acid: glucose, 1:1:1:1) was the most efficient in extracting rebaudioside A and stevioside, while NADES 36 (choline chloride: lactic acid: oxalic acid: glycerol, 2:2:1:1) extracted all targeted analytes along with untargeted compounds. The study concluded that multicomponent NADESs have excellent extractability of steviol glycosides compared to binary NADESs.