Nutraceuticals and their Derived Nano-Formulations for the Prevention and Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is one of the common chronic neurological disorders and associated with cognitive dysfunction, depression and progressive dementia. The presence of β-amyloid or senile plaques, hyper-phosphorylated tau proteins, neurofibrillary tangle, oxidative-nitrative stress, mitochondrial dysfunction, endoplasmic reticulum stress, neuroinflammation and derailed neurotransmitter status are the hallmarks of AD. Currently, donepezil, memantine, rivastigmine and galantamine are approved by the FDA for symptomatic management. It is well-known that these approved drugs only exert symptomatic relief and possess poor patient-compliance. Additionally, various published evidence showed the neuroprotective potential of various nutraceuticals via their antioxidant, anti-inflammatory and anti-apoptotic effects in the preclinical and clinical studies. These nutraceuticals possess a significant neuroprotective potential and hence, can be a future pharmacotherapeutic for the management and treatment of AD. However, nutraceuticals suffer from certain major limitations such as poor solubility, low bioavailability, low stability, fast hepatic- metabolism and larger particle size. These pharmacokinetic attributes restrict their entry into the brain via the blood-brain barrier. Therefore, to overcome such issues, various nanoformulations of nutraceuticals have been developed, that allow their effective delivery into the brain owing to reduced particle size, increased lipophilicity, increased bioavailability and avoidance of fast hepatic metabolism. Thus, in this review, we have discussed the etiology of AD, focusing on the pharmacotherapeutics of nutraceuticals with preclinical and clinical evidence, discussed pharmaceutical limitations and regulatory aspects of nutraceuticals to ensure safety and efficacy. We have further explored various nanoformulations of nutraceuticals as a novel approach to overcome the existing pharmaceutical limitations and for effective delivery into the brain.