Protective Effects of Red Onion (Allium cepa) Ethanolic Extract on Learning and Memory Impairments in Animal Model of Diabetes

Background: Onion (Allium cepa) is a plant with anti-diabetic and antioxidant properties. The aim of this study was to evaluate the protective effects of red onion ethanolic extract on learning and memory impairments in animal model of diabetes. Material and Methods: For induction of diabetes, streptozotocin (55 mg/kg) was injected intraperitoneally to male Wistar rats. Thirty two male Wistar rats were randomly divided to 4 groups (n=8). Diabetic rats located to 3 groups including 2 treatment groups with onion ethanolic extract (125 and 250 mg/kg/day) for 4 weeks and one diabetic control group. In addition, the fifth group was considered as health control group. Finally, learning and memory changes were evaluated in the Morris water maze and passive avoidance tests. Results: Our finding showed that escape latency and traveled distance was significantly increased in diabetic control compared with health control. The administration of onion extracts at 125 and 250 mg/kg significantly decreased the escape latency and traveled distance. In addition, the induction of diabetes caused a significant impairment in memory consolidation compared with health rats. However, animals received extract at 125 mg/kg spent longer time and traveled greater distance in target quarter compared with diabetic control. Our data in passive avoidance test also showed that diabetes reduced step-through latency in animals. However, administration of onion ethanolic extract onion ethanolic extract led to increased step-through latency in diabetic rats. Conclusions: Our finding showed that oral administration of red onion ethanolic extract improves learning and memory performances impaired by streptozotocin in diabetic rats.