Abstract: Objective To observe the anti-atherosclerotic effect of flavonoids extracted from leaves of Apocynum venetum and to provide evidences for therapeutic application of flavonoids in Folium Apocyni Veneti.Methods Seventy-two male Wistar rats were randomly divided into 6 groups (12 in each group):normal control,model,positive control,and low,medium,and high dose Apocynum venetum flavonoids group.All the rats were administered with vitamin D3 injection once a day for consecutive 3 days and then fed with high fat feeding for 9 weeks except for those of control group without D3 injection and with normal feeding.Then,the rats of the three flavonoids treatment groups were administered with the fluavonoids extracted from leaves of Apocynum venetum via gastric gavage once a day for 4 weeks.By the end of the treatments,aorta samples of the rats were collected and stained with Oil Red O for observing the lipid deposition; conventional paraffin specimens of aorta were prepared and stained with hematoxylin-eosin for pathological examination with light microscope.Serum total cholesterol (TC),triglyceride (TG),low-density lipoprotein cholesterol (LDL-C),high-density lipoprotein cholesterol (HDL-C),superoxide dismutase (SOD),and malondialdehyde (MDA) were detected with spectrophotometry and atherosclerosis (AS) index was calculated for all the rats.Results The rats of medium and high flavonoids group showed increased body weight and appetite compared to those of model group.In the rats treated with medium and high dose flavonoids,the Oil Red O staining observation revealed reduced areas of aorta lipid deposition and hematoxylin-eoxin(HE) staining examination presented the thickening of arterial wall and the increases in the amount of subendothelial foam cell and lipid vacuole of thoracic aorta.Compared to those of the rats in model group,significantly decreased serum TC (0.219±0.043 mol/L),TG (2.839±0.739 mol/L),LDL-C (1.856±0.471 mol/L),and MDA (6.08±3.24 nmol/mL) and increased HDL-C (0.297±0.044 mol/L) and SOD (74.33±23.67),and lower AS index were observed in the rats treated with high dose flavonoids (all P<0.05).Conclusion Total flavonoids of Folium Apocyni Veneti has an obvious anti-atherosclerotic effect and the mechanism of the effect may relate to the increased antioxidant ability in rats.