Therefore, one way to elevate ACh levels in the brain is to inhibit AChE. Furthermore, ACh is broken down in the synaptic cleft by acetylcholinesterase (AChE). This decrease results from the inability to synthesise enough ACh for sufficient transmission of information. In late stages of AD, levels of ACh have declined by up to 85%. The level of ACh in the brain of patients suffering from AD is greatly reduced compared to the healthy patients.

Furthermore, a deficiency of ACh seems to be directly correlated to AD. A low level of ACh results in impaired learning and memory as well as general “slow thinking”. The possibility to isolate pure lead compounds from the crude extracts or to administer these as nutraceuticals or as cheap alternative to drugs in third world countries make TCM plants a versatile source of natural inhibitors of AChE.īrain processing speed and memory is determined by the neurotransmitter acetylcholine (ACh). Based on these results it can be stated that some TCM plants inhibit AChE via synergistic interaction of their secondary metabolites. All extracts were also tested for their cytotoxicity in COS7 cells and none of the most active extracts was cytotoxic at the concentrations which inhibit AChE. Therefore, the mode of AChE inhibition of crude extracts of Coptis chinensis, Berberis bealei and Phellodendron chinense is probably due to of this synergism of isoquinoline alkaloids. Combinations of individual alkaloids berberine, coptisine and palmatine resulted in a synergistic enhancement of ACh inhibition. The methanol and aqueous extracts of Coptis chinensis showed IC 50 values of 0.031 µg/mL and 2.5 µg/mL, therefore having an up to 100-fold stronger AChE inhibitory activity than the already known AChE inhibitor galantamine (IC 50 = 4.33 µg/mL).

All three extracts of Berberis bealei (formerly Mahonia bealei), Coptis chinensis and Phellodendron chinense, which contain numerous isoquinoline alkaloids, substantially inhibited AChE.

In this study, methanol, dichloromethane and aqueous crude extracts from 80 Traditional Chinese Medical (TCM) plants were tested for their in vitro anti-acetylcholinesterase activity based on Ellman’s colorimetric assay. Inhibition of acetylcholinesterase (AChE) is a common treatment for early stages of the most general form of dementia, Alzheimer’s Disease (AD).

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