Background : This study was conducted to select candidates from among plant resources with the potential to improve Alzheimer’s disease (AD), the most common form of dementia. AD has been linked to a deficiency in the brain neurotransmitter acetylcholine (ACh), and is also correlated with cholinergic system abnormalities coupled with progressive cognitive impairment and altered behavior. The activity of ACh in the brain is terminated by the hydrolysis action of cholinesterase (ChEs). An inhibitor of these enzymes could contribute to improving the level of ACh and to augmenting the activity of surviving cholinergic neurons in patients with AD.
Methods and Results : Plant extracts were prepared by solvent extraction and tested for acetylcholinesterase (AChE) inhibitory activity by using the Ellman colorimetric method. One hundred and eighty-four extracts at a final concentration of 100 ㎍/㎖ were preliminarily screened for their AChE inhibition capacity. From the experiment, the AChE inhibitory activity of five extracts including a methanol extract of Coptis chinensis (rhizome), a methanol extract of Nelumbo nucifera Gaertn (stamen/ovary), a methanol extract of Persicaria tinctoria H.GROSS (flower), and both a methanol extract and a water extract of Phellaodendron amurense Rupr (bark) showed comparatively higher AChE inhibitory effects, ranging from 38.3 to 63.1%, than other extracts. The five selected extracts were retested for their AChE inhibition activity at final concentrations of 25, 50, 100, and 200 ㎍/㎖, and compared with tacrine (0.1 ㎍/㎖) as the positive control. In the experiment, the five extracts effectively inhibited AChE at each of the set concentrations.
Conclusion : The results of this study indicate that the five plant extracts mentioned above could be utilized as candidates for improving the ACh level and for ameliorating AD.