Attenuating effect of standardized lyophilized Cinnamomum zeylanicum bark extract against streptozotocin-induced experimental dementia of Alzheimer's type.

BACKGROUND: The Cinnamomum zeylanicum (CZ; family Lauraceae) bark, an important spice, has also been used traditionally for nervous stress, as a nervine tonic, and as a stimulant. Therefore, the present study was designed to evaluate the effect of the standardized lyophilized aqueous extract of CZ bark (LCZE) on learning and memory in rodents at 50, 100, and 200 mg/kg, p.o. dose levels against streptozotocin (STZ)-induced memory impairment.

METHODS: LCZE was standardized based on the cinnamaldehyde content using high-performance thin-layer chromatography (HPTLC). The effect on learning and memory was evaluated using two widely used behavioral models, the Morris water maze (MWM) test and the object recognition test (ORT). The effect of LCZE on the acetylcholinesterase (AChE) activity and oxidative stress parameters in the cerebral cortex and hippocampus of rat brain was also evaluated.

RESULTS: LCZE significantly (p<0.05) and dose-dependently attenuated STZ-induced cognitive deficit in both models in comparison to only STZ-treated animals. In the MWM test, LCZE (100 and 200 mg/kg) significantly decreased the transfer latency and increased the time spent by the animals in target quadrant. Similarly in the ORT, the LCZE-treated animals exhibited an improved discrimination between a familiar object and a novel object, indicating the reversal of STZ-induced memory impairment. LCZE also restored STZ-induced alteration in AChE activity and oxidative stress parameters in both brain parts.

CONCLUSIONS: The results clearly indicate toward the memory-enhancing effect of LCZE, which could be due to the synergistic effect of anti-AChE and antioxidant activities.