Ultrasound-assisted natural deep eutectic solvents for green extraction of flavonoids from Citri Reticulatae Pericarpium: Extraction optimization and attenuation of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory intestinal disease lacking effective treatments. Citri Reticulatae Pericarpium (CRP, Chenpi) has demonstrated efficacy in treating symptoms such as poor appetite and diarrhea in accord with UC. However, the pharmacological effects and the underlying mechanisms of CRP on UC remain unexplored. This study employed an ultrasonic-assisted extraction (UAE) technology combined with deep eutectic solvents (DESs) to extract flavonoids from CRP and clarify the underlying mechanisms in treatment of UC. A comparative study assessed the extraction performance of traditional solvents and 10 DESs, with the choline chloride and methyluren combination yielding the best results. Following this, response surface methodology (RSM) was applied for further optimization. The optimal extraction conditions were identified as liquid/solid ratio of 20 mL/g, ultrasonic power of 400 W, ultrasonic time of 52 min and water content of 65%. In vivo experiments showed that CRP can protect mice from dextran sulfate sodium (DSS)-induced UC characterized by a lower disease activity index (DAI) score, restored a distorted intestinal barrier, suppressed the inflammatory cytokines and modulated redox balance. Moreover, CRP mainly exerts its therapeutic efficacy on UC by inhibiting the expression of Myeloperoxidase (MPO), Elane and peptide-arginine deiminase 4 (PAD4). As a result, this study demonstrated that UAE-DES as a promising green alternative for the efficient extraction of bioactive compounds from plants, facilitating its future development and use in industrial settings. Moreover, CRP has potential as a candidate drug for the preclinical treatment of UC.