Role of Natural Products in the Prevention and Treatment of Alzheimer's Disease: A Comprehensive Review

Alzheimer’s disease is a multifactorial neurodegenerative disorder characterized by progressive cognitive decline, neuronal dysfunction and memory impairment. It predominantly affects older adults and represents one of the leading causes of dementia globally. The clinical manifestation of Alzheimer’s disease includes forgetfulness of recent events, difficulty recalling familiar information, impaired concentration and difficulties with planning and problem-solving abilities. The pathogenesis and progression of Alzheimer’s disease are associated with several complex interconnected mechanisms, including oxidative stress associated with mitochondrial dysfunction, intracellular accumulation of hyperphosphorylated tau proteins leading to formation of neurofibrillary tangles, extracellular accumulation of β-amyloid plaques and the contribution of genetic and environmental factors. Current pharmacological interventions are largely aimed at alleviating symptoms and slowing cognitive deterioration whilst their ability to modify the underlying pathological processes remains restricted. This clearly shows the need for novel therapeutics strategies that target multiple pathological mechanisms to address this neurodegenerative disorder. This has led to the use of natural products, particularly medicinal plants and their bioactive constituents which have attracted increasing attention from scientific and pharmaceutical communities due to their ability to distort several pathways involved in Alzheimer’s disease pathogenesis and alleviate associated symptoms. Various natural products, including flavonoids, gingerols, tannins, anthocyanins, triterpenes and alkaloids have shown potential in the prevention and treatment of several diseases. These compounds possess anti-inflammatory, antioxidant, anti-amyloidogenic and anticholinesterase activities. They function by improving synaptic function, maintaining mitochondrial activity, reducing limiting β-amyloid aggregation, inhibiting tau hyperphosphorylation, reducing oxidative stress and neuroinflammation.