Kinetics of Acetylcholinesterase Inhibition by an Aqueous Extract of Withania Somnifera Roots

Withania somnifera L. Dunal (Family: Solanaceae) is extensively used in traditional Indian medicine as a nerve tonic and is thought to improve memory. We assessed the acetylcholinesterase (AChE) inhibitory activity and kinetics of an aqueous extract of W. somnifera root, in the context of its potential role in regulating the levels of acetylcholine (ACh) in the brain. The assessment of cholinesterase inhibition was carried out using a colorimetric method based on Ellman’s reaction. Our findings demonstrate that W. somnifera extract significantly inhibited AChE in a concentration-dependent manner. A 1mg/mL extract concentration resulted in an 86% inhibition as compared with control. The IC50 value was 0.15mg/mL calculated from the equation of the percentage inhibition curve for the test extract. The Lineweaver-Burk plot indicated that the extract followed mixed non-competitive inhibition kinetics. We conclude that the mode of action exhibited by the aqueous extract of W. somnifera root has a potential therapeutic application that might be beneficial in improving memory and other cognitive functions associated with the cholinergic system.