Background:Cyathula officinalis Kuan is widely used in the clinics for the treatment of blood stasis in China.Objective:To evaluate the improving blood rheology and anti-inflammatory properties of C. officinalis Kuan extract (CO) and its active fraction (ACO) on acute blood stasis model Wistar rats and characterize the correlative constituents.Materials and Methods:CO at 0.26, 0.53, and 1.04 g/kg and ACO at 0.38, 0.75, and 1.5 g/kg were administered to acute blood stasis model Wistar rats for 3 days. Whole blood viscosity, plasma viscosity, and the levels of interleukin-6 (IL-6), nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and cyclooxygenase-2 (COX-2) in the plasma were measured. HPLC-QTOF/MS/MS method was used to identify the major constituents of ACO; the properties of two representative components (cyasterone and chikusetsusaponin IV) from ACO on thrombin-induced human umbilical vein endothelial cells damage model were also assessed by the levels of thromboxane A2 (TXA2), endothelin (ET), malondialdehyde (MDA), COX-2, endothelial nitric oxide synthase (eNOS), and superoxide dismutase (SOD).Results:CO and ACO significantly reduced whole blood viscosity, plasma viscosity, and levels of IL-6, NO, TNF-α, and COX-2 in vivo. Forty compounds were identified from ACO, mainly as phytoecdysteroids and saponins. Cyasterone and chikusetsusaponin IV could significantly inhibit levels of TXA2, ET, MDA, and COX-2 and promote the activities of eNOS and SOD in vitro.Conclusion:CO and ACO possessed significant improving blood rheology and anti-inflammatory effects on acute blood stasis model rats and the representative components Cyasterone and chikusetsusaponin IV showed significant anti-inflammatory, antioxidant, and anticoagulant effects in vitro.SUMMARY Cyathula officinalis Kuan is widely used in the clinic for the treatment of blood stasis in ChinaThe C. officinalis Kuan extract and the active fraction of C. officinalis Kuan (ACO) possessed significant improving blood rheology and anti-inflammatory effects on acute blood stasis model ratsForty compounds were identified from ACO, mainly as phytoecdysteroids and saponins Abbreviations used: TCM: Traditional Chinese Medicine, CO: Cyathula officinalis Kuan extract, ACO: Active fraction of Cyathula officinalis Kuan, ROS: Reactive oxygen species, IL-6: Interleukin-6, TNF-α: Tumor necrosis factor alpha, NO: Nitric oxide, COX-2: Cyclooxygenase-2, TXA2: Thromboxane A2, ET: Endothelin, MDA: Malondialdehyde, eNOS: Endothelial nitric oxide synthase, SOD: Superoxide dismutase, ESI: Electronic spray ionization, ELISA: Enzyme-linked immunosorbent assay, HUVECs: Human umbilical vein endothelial cells, DMEM: Dulbecco's modified Eagle medium, MMP: Matrix metalloproteinase.