BACKGROUND:The Scutellaria baicalensis is a traditional Chinese herb frequently used. Only its root is used, and its stem and leaf are abandoned in traditional custom. Inorder to make full use of medicinal material resource, the chemical component and pharmacological effects of the stem and leaf have been studied. OBJECTIVE: To observe the preventive effect of total flavones from stem and leaf of scutellaria baicalensis on experimental hyperlipidemia in rats. DESIGN: Randomized controlled trial. SETTING: Institute of Traditional Chinese Medicine, Chengde Medical College MATERIALS: The experiment was conducted in the Institute of Traditional Chinese Medicine, Chengde Medical College from March 1999 to January 2000. Totally 60 male Wistar rats with beginning body mass(200±10)g were provided by Experimental Animal Research Institute, Chinese Academy of Medical Science (Qualification No.01-3008). INTERVENTIONS: Sixty rats were randomly divided into 6 groups:normal control group, high-lipid model group, the groups of 12.5, 25 and 50 mg/kg of total flavonoids (TF group) and clofibrate group (25 mg/kg),with 10 rats in each group. The rats in the normal control group were fed with basic feed. The rats in the high-lipid model group were fed with highlipid feed.Rats in the TF group and clofibrate group were fed synchronously with high-lipid feed and total flavonoids or clofibrate for consecutive 30 days. The change of blood lipid was observed. MAIN OUTCOME MEASURES: The levels of total cholesterol (TC),triglyceride (TG), low density lipoprotein (LDL-C), high density lipoprotein (HDL-C) in the serum of all the rats were measured with CL-7200 type automatic biochemistry analytical instrument at the end of the experiment, and the atherosclerosis indexes (AI) were calculated (AI=TC-HDL-C/HDL-C).RESULTS: Totally 60 rats entered the result analysis. ① Level of TC in the serum of rats: The level in the high-lipid model group was significantly higher than that in the normal control group[(5.01 ±1.05,2.33±0.35)mmol/L, (P ＜ 0.01 )]; The level in the groups of 12.5 mg/kg, 25 mg/kg and 50 mg/kg of TF was (4.15±1.12, 3.03±0.31,2.98±0.56)mmol/L, there was no significant difference between group of 12.5 mg/kg of TF and model group (t=1.74, P ＞ 0.05), but there was significant difference between groups of 25 mg/kg and 50 mg/kg of TF and model group (t=5.66-5.23, P ＜ 0.01). ②Level of TG in the serum of rats: The level in the groups of 12.5 mg/kg, 25 mg/kg and 50 mg/kg of TF was (1.22±0.56)mmol/L,(1.56±0.41)mmol/L,(1.24 ±0.45)mmol/L respectively, compared with model group(2.14±0.74) mmol/L, there was significant difference (t =2.19-3.45, P ＜ 0.05-0.01). ③ LDL-C level of the serum in the rats: The level in the groups of 12.5 mg/kg, 25 mg/kg and 50 mg/kg of TF was (2.67 ±0.45) mmol/L, (1.41 ±0.23)mmol/L, (1.29±0.23) mmol/Lrespcrtively,compared with model group[(3.94±0.42)mmol/L, there was significant difference (t=5.77-12.71, P ＜ 0.05-0.01). ④ HDL-C level of the serum in the rats: the level in the groups of 12.5 mg/kg, 25 mg/kg and 50 mg/kg of TF was (0.72±0.23)mmol/L,( 0.91±0.32)mmoL/L,(1.05±0.23)mmoL/L respectively, there was no significant difference between group of 12.5 mg/kg of TF and model group[(0.56±0.21)mmol/L, but there was significant difference between groups of 25 mg/kg and 50 mg/kg of TF and model group (t=2.92-4.38,0.05 ,P ＜ 0.05-0.01).⑤AI: the level in the groups of 12.5 mg/kg, 25 mg/kg and 50 mg/kg of TF was(2.96 ±1.35), (2.10±0.97), (1.55±0.41)respectively, compared with model group (4.23±0.65) , there was significant difference (t =3.54-9.49 ,P ＜ 0.01). CONCLUSION: TF has significantly inhibitory effect on the increase of TC, TG and LDL-C in the serum of the rats induced by high-lipid feed; it can also increase the level of HDL-C, indicating TF has obviously preventive effect on experimental hyperlipidemia in rats.