Alzheimer's disease (AD) is a neurodegenerative disease of the brain associated with decrease of cognitive function, memory impairment, and behavioral changes. More than 25 million people in the world today are affected by dementia, most suffering from Alzheimer's disease. In both developed and developing nations, Alzheimer's disease has had tremendous impact on the affected individuals, caregivers, and society. The duration of the disease can vary between 5 years and 20 years. The general therapeutic approaches are reliant on the use of acetyl cholinesterase inhibitors (AChE) which can preserve brain cholinergic nerve function in some patients. With the advances in studies of the pathogenic mechanisms in AD. The target of new AD drug development has been directed to modifying the pathology.