ABSTRACT
Neurodegenerative disease is a broad medical condition, associated with progressive brain dysfunction and structural damage to functional neurons, resulting in neuronal cell death. Alzheimer’s disease (AD) is one of the most common age-related neurodegenerative diseases. Among today's world population, around 33.9 million people are affected by AD, and this number will triple over the next 40 years. The main characteristic features of AD are the gradual decline of a person’s memory and ability to learn, reason and carry out daily activities due to the accumulation of amyloid-beta 42 (Aβ42) plaques in the neurons. These Aβ42 plaques trigger oxidative stress and abnormal signaling in the neuron. Plaque development begins with the neuronal accumulation of the amyloid precursor protein, followed by its deposition into the extracellular space between two neurons or microglia, resulting in Aβ peptide accumulation. The amyloid precursor protein can be proteolyzed directly by β-secretase, a process that generates the Aβ protein in the brain. It has been reported that loss of the neurotransmitter, acetylcholine, is responsible for the total dysfunction of cholinergic neurotransmission that is observed in AD. Acetylcholinesterase (AChE) is the primary enzyme responsible for the breakdown of acetylcholine within synapses of the cerebral cortex, and, consequently, AChE inhibitors have been employed for the treatment of AD. Various plant compounds are already being used as AChE inhibitors for the treatment of AD, such as rivastigmine, donepezil, and galantamine. Medicinal plants offer an alternative option to conventional allopathic medicines to ameliorate the symptoms of AD.
There are more than 400,000 plant species on earth, representing an enormous wealth of medicinal remedies from Mother Nature. Natural products and their derivatives represent more than 40% of all the drugs used in modern medicine. Because of the low success rate and high investment cost of developing modern drugs, today’s conventional pharmaceuticals are very expensive. Today, the sales of plant-derived antimicrobial, cardiovascular, antidiabetic, immunosuppressive, anti-Alzheimer's, and anticancer drugs exceeded US$85 billion in 2013. Ethnopharmacology screening of plant active ingredients may provide useful leads in the discovery of new drugs for therapy of AD. In this chapter, we discuss the screening of medicinal plants and their active compounds for chemicals capable of treating AD.
