Inhibitory effects of ethanolic extract of Cyperus rotandus on acetylcholinesrerase activity

Dementia is a progressive decline in mental and cognitive abilities which may be caused by brain injury or disease. Among several types of dementia, Alzheimer disease (AD) is the most prevalent. Acetylcholine is one of the mediators in brain which has a key role in recording, maintenance and recall of information in the brain. Neuronal cells secreting acetylcholine are among the first cells which are injured in Alzheimer disease. Prevention of degradation of acetylcholine by inhibition of acetylcholinesrerase can be essential for maintenance of memory and thinking. Considering increasing need for medicines with fewer side effects for the treatment of diseases such as AD, in this study we investigated the inhibitory effect of an extract of the Cyperus rotandus on the activity of acetylcholinestras. Activity of the enzyme acetylcholinesterase (AchE) was measured by Ellman method, using AWT IMAGEScale. Then, Lineweaver Burk plot was used to calculate Km, Vmax and Ki. In all the phases, the enzyme concentration was constant and its activity was measured in six different concentrations of acetylthiocholine (5, 10, 15, 20, 25 and 30 mM) at room temperature (250- 270C) based on optical absorption at 412 nm wavelength. Experiments were conducted in the presence of various concentrations of physostigmine (5.0, 75/0, 1, 1.5 and 2 mg/100ml) and Cyperus rotandus (1.0, 2.0, 3.0, 4.0, 5.0, 6.0 and 7/0 mg / ml). Finally, according to Dixon plot we used different levels of inhibitor concentration and activity percentages to calculate IC50 of inhibitors. Ki of Cyperus rotandus was found to be almost 40 times greater than Ki of physostigmine. Values of IC50 of physostigmine and Cyperusrotandus were 2.21μg/ml and 139μg/ml, respectively. Considering the mechanism of enzyme inhibitory effect, lower levels of Ki and IC50 will lead to higher inhibitory effects. Therefore, the results showed that physostigmine was a stronger inhibitor compared to Cyperus rotandus. Moreover, with purification of the extract, higher inhibitory effects could be expected. In addition, Cyperus rotandus does not have the side effects such as nausea, vertigo, etc. which can be produced by physostigmine.