Figure 1.

Current drugs of choice for Alzheimer’s disease (AD) therapy. Natural products are at the forefront of drug discovery for AD as galantamine was first isolated from the bulbs of the common snowdrop plant Galanthus nivalis. Isolated from the West African Calabar bean, physostigmine has been the prototype acetylcholinesterase (AChE) inhibitor, but its short duration of effect for AD and tacrine’s toxicity initiated the search for safer drugs; this led to the discovery of donepezil as a synthetic AChE inhibitor. Memantine acts through a different mechanism of action and was obtained from the synthesis source.