As a traditional Chinese medicinal herb in China, Fructus Aurantii is widely used and has a long history. It is often used in combination with other medicinal herbs in many classic prescriptions, and has the effects of breaking down qi, eliminating accumulation, resolving phlegm, and dispersing phlegm. Modern pharmacology has found that the characteristic bioactive ingredient of Fructus Aurantii is mainly the alkaloid sinomenine, which belongs to the alkaloid class. It exists in three isomers, namely p-sinomenine (para position), m-sinomenine (meta position), and o-sinomenine (ortho position). Its structural formula is shown in Figure 1, but p-sinomenine is naturally present in plants and has the highest content. In Western countries such as the United States, sinomenine is commonly used in weight loss products, while in South Africa, it is used to treat conditions such as insomnia, anxiety, and epilepsy. Simulin also has numerous physiological activities such as regulating glucose and lipid metabolism, anti depression, improving gastrointestinal function, and anti-cancer. In addition, Simulin has shown great potential in the treatment of Parkinson’s disease and hair loss.
At present, traditional organic solvents such as methanol, ethanol, chloroform, and ethyl acetate are widely used to extract natural active compounds from plants. However, this often has inherent drawbacks such as high energy consumption, environmental pollution, and solvent residue. Therefore, it is necessary to find new and efficient green solvents for the extraction of natural active substances. With the concept of green extraction, deep eutectic solvents (DES) were first proposed in 2003 and defined as a mixture composed of hydrogen bond acceptors (HBA) and hydrogen bond acceptors (HBD), which are mainly bound together through hydrogen bonds and van der Waals forces. DES has been applied in various fields such as catalytic chemistry, electrochemistry, materials chemistry, biochemistry, biology, and organic synthesis due to its low cost, flexible proportioning, low toxicity, recyclability, and environmental friendliness. In addition, DES has been reported in multiple literature as a new environmentally friendly solvent for the extraction of natural bioactive substances, with excellent extraction efficiency for natural active compounds such as flavonoids, polysaccharides, phenolic acids, alkaloids, saponins, and anthraquinones. Although there have been few literature reports on the application of DES as an extraction solvent for extracting active substances from Fructus Aurantii or Fructus Aurantii, there are currently few types of DES used for extracting active substances from Fructus Aurantii or Fructus Aurantii, and the target substances extracted are limited to flavonoids. There have been no research reports on ultrasound assisted DES extraction of Fructus Aurantii and Fructus Aurantii sinapine.
This study used Chongqing Tongnan Fructus Aurantii as raw material and proposed for the first time the use of DES instead of traditional organic solvents for ultrasound assisted extraction of sinomenine from Fructus Aurantii. When preparing DES, HBA selects commonly used choline chloride and betaine, while HBD contains sugar based, alcohol based, amide based, and organic acid groups to screen for the DES with the best extraction effect. The system optimized process parameters such as liquid to material ratio, extraction time, and ultrasound power, and conducted preliminary kinetic analysis on the extraction process of Fructus Aurantii Sinensis. A kinetic model for ultrasound assisted deep eutectic extraction of Fructus Aurantii Sinensis Sinensis was established, providing a certain reference for the application expansion of DES and the optimization of the extraction process of Fructus Aurantii Sinensis Sinensis.

This study established for the first time an ultrasound assisted extraction method for sinomenine from traditional Chinese medicine Fructus Aurantii using deep eutectic solvents as extraction solvents. Among the 20 selected deep eutectic solvents, DES (water content 50%) composed of betaine monohydrate: lactic acid (1:3) has a better extraction effect. The optimal extraction conditions are: liquid to material ratio of 39mL/g, ultrasound power of 220W, and ultrasound time of 20min. Under the optimal extraction conditions, the yield of sinomenine was 0.4284%. Compared to common extraction solvents and methods, the extraction yield of betaine lactate monohydrate DES is higher and the extraction time is shorter. Therefore, this method can be successfully applied to the extraction of sinomenine from plant matrices, providing a sustainable and safe extraction process for the analysis and preparation of sinomenine in complex samples, with the potential for large-scale industrial applications.
Establishing a kinetic model for the extraction of plant active ingredients is the basis for quantitatively studying their dissolution patterns. In this study, the mass concentration of sinomenine was measured at different ultrasound powers and extraction times. Based on Fick’s second law, a kinetic model for ultrasound assisted deep eutectic solvent extraction of sinomenine from Fructus Aurantii was established and derived for verification. By calculating and fitting the data, kinetic parameters were obtained. As the ultrasound power increased, the rate constant increased, the half-life decreased, the diffusion coefficient increased, and the relative recovery rate decreased. The research results can provide theoretical references for in-depth research on extracting active ingredients from plant materials.