Enhanced extraction efficiency of natural D-borneol from Mei Pian tree leaves pretreated with deep eutectic solvents

Stems and leaves of Mei Pian tree can be used to extract natural D-borneol. In this study, a variety of deep eutectic solvents (DESs) based on choline chloride were used to pretreat leaves of Mei Pian tree, from which natural D-borneol was extracted by Soxhlet extraction. The extraction efficiency of most pretreated leaves was higher than that of the unpretreated leaves, and that pretreated by DES based on choline chloride and sucrose or choline chloride and glycol was maximal. Moreover, The Box-Behnken design (BBD) of response surface method was used to optimize the water content, temperature, and pretreatment time. The optimal conditions included pretreatment of Mei Pian tree for 4.07 hr at 44.5°C by DES, which was synthesized using choline chloride, sucrose, and water at the molar ratio of 5:2:5.9, and the extraction efficiency (4.936 mg/g) was maximal, more than twice as much as that of unpretreatment. The results showed that the pretreatment process using DES based on choline chloride and sucrose could effectively improve the extraction efficiency of natural D-borneol from Mei Pian tree.