Protective effect of Morinda citrifolia fruits on β‐amyloid (25–35) induced cognitive dysfunction in mice: An experimental and biochemical study

The neuroprotective effect of an ethyl acetate extract of Morinda citrifolia (Rubiaceae) Linn. fruits (EMC, ethyl acetate extract of Morinda citrifolia) at doses of 200 and 400 mg/kg, p.o. was studied on β‐amyloid (25–35) peptide induced cognitive dysfunction in mice. In the step‐down inhibitory avoidance, EMC exhibited a significant increase in short‐term memory and long‐term memory (p < 0.05). A significant decrease (p < 0.01) in escape latency was noticed in the animals in the water maze. A significant increase (p < 0.01) in alteration of behavior was exhibited upon administration of EMC 200 and 400 mg/kg on the Y maze. Exploratory parameters such as line crossings, head dipping and rearing were increased significantly in EMC treated groups in a dose‐dependent manner (p < 0.05 and p < 0.01). A significant reduction (p < 0.05) in acetyl cholinesterase activity was noticed in the EMC 200 and 400 mg/kg treated groups. The level of monoamine oxidase‐A was decreased by the administration of EMC 200 and 400 mg/kg (p < 0.05 and p < 0.01, respectively). EMC at a dose of 400 mg/kg exhibited a significant increase (p < 0.01) in the levels of serotonin and dopamine. Antioxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione peroxidase and ascorbic acid were decreased significantly in the b‐amyloid peptide injected group, whose levels were restored significantly (p < 0.01) by the administration of EMC (400 mg/kg). Copyright © 2009 John Wiley & Sons, Ltd.