Phytotherapeutic agents for neurodegenerative disorders: A neuropharmacological review

Abstract Neurodegenerative disorders are very complex, multifactorial, and fatal diseases in which neurons are degenerated leading to cognitive and muscular problems. There are no specific treatments available for these diseases. The drugs that are available in the market offer symptomatic relief with improvement in the daily functions to some extent. So, phytochemicals with multifactorial efficacy can be promising substances for the treatment of neurodegenerative diseases. Multiple diseases like Alzheimer’s disease, Parkinson’s disease, Amyotrophic lateral sclerosis, Huntington’s disease, and stroke have been reported to have been prevented by various plant and plant products. Phytochemicals act by various properties like antioxidant and antiinflammatory agents thereby reducing oxidative stress and increasing overall antioxidant load of the nerve cells. They can also restore the mitochondrial function, which is known to be disrupted in case of these diseases, e.g., resveratrol, and acts as enhancers of mitochondrial biogenesis. They are also reported to have antiapoptotic effects and have been known to restore neuronal cell death by acting as agonists of neurotrophic factors inducing neuroprotection. Several polyphenols like genistein, resveratrol, quercetin, and catechins have been reported to have the potential to enhance the cell-signaling pathways associated with neuronal survival while others act as nonaggregators of misfolded proteins which are almost found in all types of neurodegenerative diseases. Apart from the available phytochemicals, presently their nanoformulations are also being used as therapeutics for various kinds of neurological diseases, and it has been found that, in many diseases, their efficacy is better than the parent phytochemical, probably because they can effectively cross the blood-brain barrier (BBB), which could be a promising approach in the line of treatment. This chapter deals with the most common neurodegenerative disorders, their mode of progression, and the previously stated mechanisms of action of the phytochemicals specific to different diseases. The use of the nanoformulations targeting these diseases are also at the core of this chapter.