Objective To investigate the effect of Citronella oil on dementia of Alzheimer's type induced by D-galactose and aluminum trichloride (AlCl3) and explore its mechanism.Methods The 60 healthy KM mice with sex in half were enrolled in this study,10 of them were taken randomly as the normal group,the remainder 50 mice were in the model group.The rats received inntraperitoneal injection of D-galactose and oral aluminum trichloride for consecutive 10 weeks to construct the disease models.The model rats were randomly divided into five groups:model group,control group (0.5 g · kg-1 Piracetan) and three doses (0.4,0.6,0.8 mL · kg-1 Citronella oil) experimental groups.The ability of learning and memory was measured by the Morris water maze test.The levels of glutathione peroxidase (GSH-PX) and malondialdehyde (MDA) in serum homogenate and acetylcholine (ACh) in brain tissue homogenate were determined by spectrophotometer.Results At the fifth day in the Morris water maze training period,the escape latency(EL;s) in the normal group,model group,control group and three doses experimental groups were 21.42 ±-3.18,43.33 ± 2.14,26.84 ± 0.71,23.16 ± 3.70,18.48 ± 1.11,21.40 ±0.88.Compared with the normal group,the EL in model group was increased significantly (P ＜ 0.05).Compared with the model group,EL in control group and three doses experimental groups reduced significantly (P ＜ 0.05).The levels of GSH-PX and MDA in serum in the normal group,model group,control group and three doses experimental groups were (299.05 ± 90.62),(246.19 ± 37.90),(532.49 ± 121.52),(587.21 ± 177.37),(497.14 ±82.95),(493.33 ±73.64)U · mL-1;(9.38 ±3.01),(14.89 ±4.41),(6.98 ±2.43),(6.06 ±3.34),(5.26 ± 1.90),(5.01 ± 1.59) mmol · mL-1.Compared with the normal group,the GSH-PX and MDA in model group was decreased or increased significantly (all P ＜ 0.05).Compared with the model group,the GSH-PX and MDA in control group and three doses experimental groups reduced significantly (P ＜ 0.05,P ＜ 0.01).The level of ACh in brain tissue in the normal group,model group,control group and three doses experimental groups were (268.27 ±25.40),(224.95 ±21.52),(392.56 ±50.58),(240.17 ± 17.15),(255.50 ± 15.91),(259.15 ±20.74) μg · mL-1.Compared with the normal group,the ACh in model group was decreased significantly (P ＜ 0.01).Compared with the model group,the ACh in control group and middle and high doses experimental groups increased significantly (P ＜ 0.05,P ＜ 0.01).Conclusion Citronella oil,like Piracetam,enhanced the antioxidant activity of the Alzheimer's type induced by D-galactose and AlCl3,and increased the synthesis of ACh in brain.