A green and integrated strategy for enhanced phenolic compounds extraction from mulberry (Morus alba L.) leaves by deep eutectic solvent

Green and tailor-made deep eutectic solvents (DESs) coupled with microwave-assisted extraction (MAE) were performed to extract phenolic compounds from mulberry leaves. Among the twelve DESs prepared, Choline chloride/Glycerol (1:2) with 20% water content was more efficient to get high extraction yields of phenolics. Then, several essential parameters of microwave-assisted deep eutectic solvents extraction (DES-MAE) were optimized by single-factor and Box-Behnken design (BBD) experiments. According to the result of optimization, the total extraction yield of target phenolic compounds reached 8.352 mg/g at microwave temperature 66 o C for extracting 18 min with the liquid/solid ratio of 20 mL/g, which was obviously superior to conventional solvent extraction. In addition, the extraction kinetic models confirmed that microwave-assisted extraction was a more efficient extraction technique than ultrasound-assisted extraction and heat-refluxing extraction. Meanwhile, the macroporous resin was utilized to enrich and separate target compounds from DES extracts, and the recovered DES still exhibited a good solvent effect to be applied for re-extraction. Therefore, DES-MAE followed by macroporous resin column chromatography was a green and integrated strategy for the extraction and preparative separation of active ingredients from plant materials.