Effect of different extracts of Centella asiatica on cognition and markers of oxidative stress in rats.

Centella asiatica, a plant mentioned in Indian literature has been described to possess CNS effects such as stimulatory-nervine tonic, rejuvenant, sedative, tranquilizer and intelligence promoting property. In the present study aqueous, methanolic and chloroform extracts of C. asiatica were investigated for their effect on cognitive functions in rats. Male Wistar rats of 200-250 g were used to study the effect on learning and memory by using shuttle box, step through, step down and elevated plus maze paradigms. Only the aqueous extract of whole plant (200 mg/kg for 14 days) showed an improvement in learning and memory in both shuttle box and step through paradigms. Therefore, further experiments were conducted with aqueous extract using 100, 200 and 300 mg/kg doses in different paradigms of learning and memory. All doses of aqueous extract increased the number of avoidances in shuttle box and prolonged the step through latency in step through apparatus in a dose dependent manner, while only two doses 200 and 300 mg/kg of aqueous extract showed significant increase in the step down latency in step down apparatus and transfer latency (TL) in elevated plus maze. Among doses of aqueous extract tested on oxidative stress parameters, only 200 and 300 mg/kg showed a significant decrease in the brain levels of malondialdehyde (MDA) with simultaneous significant increase in levels of glutathione. There was a significant increase in the levels of catalase at the 300 mg/kg but no significant change in superoxide dismutase (SOD) levels were observed. The present findings indicate that the aqueous extract of C. asiatica has cognitive enhancing effect and an antioxidant mechanism is involved.