causes oxidative stress and dysfunction of the liver. This study was undertaken to evaluate the effects of the hydroalcoholic extract of Terminalia chebula, on some biochemical and histopathological parameters of liver tissue in diazinon-administered rats. Materials and Methods: Wistar rats were orally administered with 25 mg/kg body weight diazinon. Vehicle (distilled water) and silymarin (50 mg/kg body weight) were used as the negative and positive control groups, respectively. Diazinon-administered groups were treated with T.chebula (Terminalia chebula) fruit extract (200, 400, and 800 mg/kg). After 15 days of treatment, the blood specimens and liver samples were examined. Results: In diazinon-treated group, the levels of serum urea, high density lipoprotein (HDL), and liver superoxide dismutase (SOD), catalase (CAT), and vitamin C significantly decreased (p<0.05) compared to control. Also, in this group, serum triglyceride (TG), total cholesterol (TC), very low density lipoprotein cholesterol (VLDL), protein carbonyl (PC), malondialdehyde, tumor necrosis factor-α (TNF-α), and TNF-α
gene expression significantly increased (p<0.05) as compared to the control (vehicle-treated rats). Treatment with T. chebula resulted in a significant increase (p<0.05) in CAT, SOD, vitamin C, HDL and a significant decrease (p<0.05) in the level of urea, MDA, PC, TG, TC, VLDL, TNF-α
protein, and the gene expression of TNF-α
compared with test without treatment group. Histopathological evidence demonstrated that treatment with T. chebula extract could decrease liver lymphocyte infiltration. Conclusion: The present study suggests that T. chebula fruit extract has protective effects against diazinon-induced oxidative stress.