**5.1 Interaction of donepezil with brain cystatin**

Alzheimer's disease is a progressive brain disorder that gradually destroys a person's memory and ability to learn, reason, and make judgments. AChE is responsible for degradation of the neurotransmitter acetylcholine (ACh) in the synaptic cleft of neuromuscular junctions and of neuronal contacts in the central nervous system [22, 23]. Donepezil belongs to the important class of acetylcholinesterase inhibitors (AChEIs) [24]. The results of the interaction of donepezil with cystatin are given below.
