Objective To prepare quercetin ( QUE) loaded chitosan nanoparticles ( CS-NPs), evaluate its physicochemical properties and antioxidation activity in vitro.Methods Quercetin chitosan nanoparticles were prepared by ionic crosslinking method and self-assembly method.The preparation method was optimized using entrapment efficiency (EE), drug loading (DL) and size as indexes.The best formulation and preparation conditions were optimized by orthogonal test based on single-factor test, evaluation indicator as particle size and EE.The physicochemical properties of the obtained QUE-CS-NPs were characterized by the following methods: the transmission electron microscope (TEM), dynamic light scattering (DLS) analysis for morphology, size distribution and Zeta potential.In vitro release behavior in 0.5% SDS solution was evaluated by dialysis tube method.In vitro antioxidant activity assays were performed by evaluating the abilities of the microspheres for hydroxide radicals and superoxide anions .Results TEM results revealed QUE-CS-NPs with round and uniform.Particle-size analysis showed that the diameters and Zeta potential of the QUE-CS-NPs were (282.9 ±20) nm and (30.5 ±2) mV, with uniform distribution (polydispersity below 0.185).DL and EE of QUE-CS-NPs were (8.81 ±0.65) %and (80.02 ±1.04) %, respectively.QUE-CS-NPs showed extended administration times with 66.2% cumulative release within 72 h.QUE-CS-NPs showed pronounced antioxidant activity and a concentration dependent, even more substantial than that of pure QUE.Conclusion QUE-CS-NPs show a good size, sustain release effect and pronounce antioxidant activity.

Pain is one of the most prevalent health problems. Current medications for pain are mainly anticonvulsants， tricyclic antidepressants， and opioidergic drugs. However， their therapeutic effectiveness is limited during application， and some even have severe side effects. In recent years， research on natural ingredients from Chinese herbal medicine has been extensively conducted for their analgesic activities. A series of natural ingredients represented by alkaloids， coumarins， flavonoids， and terpenoids have shown great analgesic activity， and further studies on their analgesic mechanism have found that most natural products have multi-target analgesic mechanisms. It can exert analgesic effects by blocking ion channels， regulating related receptors， or inducing anti-inflammatory or antioxidant effects. In addition， many traditional Chinese medicine （TCM） formulas have shown great analgesic ability after clinical application and have multiple complex analgesic mechanisms. The drug cloud （dCloud） theory can better describe the mechanisms， and it can represent the complete therapeutic spectrum of multi-target analgesics from two dimensions， namely the "direct efficacy" that directly inhibits pain signals and the "background efficacy" that targets the root causes of pain. The authors summarized the research progress of natural ingredients with analgesic effects found in Chinese herbal medicine so far， as well as the analgesic efficacy and potential mechanisms of TCM formulas with great analgesic effects in clinical applications， so as to provide a new basis for searching for new analgesic drugs from TCM.