Cognitive enhancement activity of turmeric oil in amyloid beta (25-35) induced Alzheimers model

Abstract

Introduction: Turmeric oil (TMO) is a secondary metabolite of Curcuma longa Linn obtained by steam distillation of its rhizomes. It contains 50% ar-Turmerone as a major constituent. The antioxidant, anti-bacterial and anti- inflammatory activities of the Turmeric oil have already been established. It has been reported that, Curcumin (CM) is having a protective role in neuro inflammation and beneficial in Alzheimers disease (AD). But the effect of TMO (fraction without CM) is not explored till now. Aim: To evaluate the cognitive enhancement activity of turmeric oil using Amyloid Beta induced Alzheimers model and comparing it with that of Curcumin. Methodology: An ICV injection was performed to administer A? (25-35) peptide to both the lateral ventricles of the Wistar albino rats. Turmeric oil (400mg/kg), Curcumin (400mg/kg) and Donepezil (DPL) 10mg/kg were suspended in sunflower oil and administered orally from the second day of ICV injection. After 16 days of recovery period, in-vivo screening for spatial working, spatial learning and recognition memory were performed by Radial arm maze, Morris water maze and Novel object recognition task respectively. In-vitro study of acetyl cholinesterase inhibitory activity was also performed by modified Ellmans method. Results: TMO significantly reduced the number of wrong entries in Radial arm maze compared to the A? group. DPL showed maximum reduction in number of wrong entries followed by CM and TMO. In Morris water maze task, TMO significantly reduced the escape latency when compared to the A? group. The effect of DPL in escape latency was more significant compared to CM and TMO. In Novel object recognition task, TMO could not alter the percentage time spent on the novel object compared to the A? group. DPL and CM significantly increased the percentage time spent on the novel object. Acetyl cholinesterase inhibitory activity of TMO, CM and DPL were 53.37%, 58.26% and 66.35% respectively at 10mg/ml concentration which denotes the enhancement of acetyl choline in brain. TMO provides a significant protection against spatial working and learning memory impairment, while its effect was not much affected in recognition memory impairment. Conclusion: It is concluded that Turmeric oil enhances the cognitive activity compared to Curcumin and Donepezil.