Acetylcholinesterase inhibitory activity of selected plants used in TCM to improve cognitive function

As people are becoming older, mental degeneration in the form of Alzheimer's disease, Parkinson's disease and different types of dementia is a major public health concern. Alzheimer's disease is the most common form of dementia diagnosed after the age of 60 worldwide. It is a chronic and progressive process and a multifaceted neurodegenerative disorder affecting different brain areas. Currently, acetylcholinesterase (AChE) inhibitors are the main class of drugs prescribed for symptomatic treatment of Alzheimer's disease. However, these only slow down the disease progression. A cure for Alzheimer's disease has yet to be found. Plants from all over the world are being investigated intensively for compounds with AChE inhibiting activity.

In the context of a recent study, 31 plants used in Traditional Chinese Medicine for the improvement of memory and cognition in old age were tested for their acetylcholinesterase inhibitory properties (in vitro) using a modified version of the colorimetric method of Ellman [1]. The final product was detected photometrically at 412nm. The plant material was extracted with water in the traditional Chinese way.

Significant inhibition of the enzyme expressed by the IC50 values was observed for the aqueous extracts from Rhiz. Coptidis (huáng lián; IC50=4.68µg/mL), Rad. Angelicae sinensis (dāng guī; IC50=0.13µg/mL) Rad. Paeoniae alba (bái sháo; IC50=0.59µg/mL), and Fr. Viticis (màn jīng zĭ; IC50=0.53µg/mL). These results substantiate the traditional use of the investigated plant parts for improvement of cognition.

Reference: [1] Ellman, G.L. et al. (1961) Biochem. Pharmacol 7:88–95.