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A novel ternary deep eutectic solvent (DES), consisted of choline chloride, oxalic acid and ethylene glycol, was developed as a green, low-cost and recyclable pretreatment system for multi-stage utilization of Eucommia ulmoides seed shells. Under optimum conditions, 79.7 % hemicellulose and 65.6 % lignin were quickly removed while 84.0 % cellulose was retained. After DES pretreatment, the yield and purity of gutta-percha achieved 85.1 mg/g and 96.2 %, which increased 1.4 and 1.8 folds higher than that of un-treatment ones. Meanwhile, 69.1 % enzymatic digestibility of cellulose was obtained, that was 2.3 folds higher than that of raw substrates. Moreover, 53.6 % low-condensation lignin with aromatic structures and valuable aryl-ether linkages was well collected. Importantly, the DES that has been recycled five runs can still remove 73.9 % hemicellulose and 58.0 % lignin. Overall, the DES was determined to efficiently promote the separation and conversion of high-quality gutta-percha, value-added lignin and high-yield glucose from Eucommia ulmoides seed shells.

In this work, an efficient and environmentally friendly extraction process was proposed to simultaneously obtain iridoids and phenolic acids from Eucommia ulmoides Oliver leaves (EUL). Namely, the integrated microwave-assisted ternary deep eutectic solvent extraction (TDES-MAE), which was firstly applied to extract compounds from EUL for the first time. In the tailor-made TDES system, tiny ascorbic acid (Vc) was added to modify the acidity of the binary deep eutectic solvents (BDES)composed of a 1:2 M ratio of Choline chloride/1,4-butanediol)to form TDES, which possess a higher extraction yield than BDES. Some factors including DES types, molar ratio, water content and selection of hydrogen bond donor (HBD) were investigated to get the superior TDES solvent. Then Box-Behnken design was implemented to acquire the optimum conditions, such as extraction time, extraction temperature, liquid-solid ratio were optimized by using response surface methodology (RSM). Under the optimal conditions, extraction efficiency of the TDES-MAE was significantly increased and 1.4-fold to the traditional method. Meanwhile, the excellent recovery and the antioxidant activity shown that the extraction system based on tailor-made TDES was economically productive and efficient for extracting more beneficial products from plants.