Ultrasonic-assisted deep eutectic solvent to extract camptothecin and 10-hydroxycamptothecin from Camptotheca acuminata fruits: optimization, purification, structural characterization, and mechanisms research

Camptothecin (CPT) has significant biological activity and has been extensively studied. This study established an efficient and green ultrasonic-assisted deep eutectic solvent (UAE-DES) and combined it with macroporous resin purification technology to extract and purify CPT and 10-hydroxycamptothecin (HCPT) from Camptotheca acuminata fruit. In total, 33 natural DES were prepared, among which choline chloride-1,4-butanediol was the most effective. The single-factor and response surface optimization extraction experiments were carried out to determine optimal conditions as follows: ultrasonic time = 27 min, solid-liquid ratio = 1:35 g/mL, ultrasonic temperature = 70 °C, DES moisture content, = 29 %, and total extraction rate = 0.1318 %. Furthermore, the scanning electron microscopy revealed that the UAE-DES treatment significantly disrupted the cell-wall structure of C. acuminata fruits, promoting the release of the target constituents. Moreover, AB-8-type macroporous resin was employed to optimize adsorption and desorption, which optimized 63.4 % and 77.3 % adsorption and desorption of CPT and HCPT, respectively. Density functional theory (DFT) was employed for assessing electrostatic potential (ESP), complexation energy, and reduced density gradient (RDG), to identify the non-covalent interactions between DES, conventional solvent ethanol, and CPT-like compounds during the extraction process. This study comprehensively explained the extraction mechanism and confirmed that DES had better extraction potential and good biocompatibility. These findings provide a theoretical basis and technical support for the green and efficient extraction and purification of CPT-like compounds.