Ameliorative effect of ellagic acid against diabetes-induced memory deficit in rats: the role of oxidative stress

Diabetes mellitus is associated with memory impairment. Ellagic acid (EA) is a natural polyphenol with anti-diabetic and neuroprotective effects. The aim of the present study was to investigate the protective effect of ellagic acid on diabetes induced memory impairment and to evaluate the role of its antioxidant effect. Male Wistar rats were randomly divided into four groups (n=8): control, diabetic, diabetic receiving 25 mg/kg of EA, and diabetic receiving 50 mg/kg of EA. Diabetes was induced by a single intraperitoneal injection of 60 mg/kg of streptozotocin (STZ). After receiving EA (once a day) by oral gavage for four weeks, passive avoidance learning (PAL) test was used to evaluate memory. Finally, oxidative stress related factors including malondialdehyde (MDA) and total antioxidant capacity (TAC) were evaluated in the hippocampal tissue separated from the animal brains under deep anesthesia. Diabetic animals showed marked reductions in step-through latency (STLr) and elevation in time spent in the dark compartment (TDC)  in the retention trial and elevation of MDA level and diminution of TAC compared to controls significantly. Treatment of diabetic rats with EA markedly increased STLr, decreased TDC and enhanced TAC (by both EA doses) and reduced MDA (at a dose of 50 mg/kg of EA). The results displayed learning and memory improving effect of EA in diabetic rats via attenuating oxidative stress.