Multitarget Actions of Pentacyclic Triterpenic Acids in Alzheimer's Disease: Mechanistic Insights.

Alzheimer's disease (AD) is a complex neurodegenerative disorder with features of amyloid-beta (Aβ) accumulations, tau hyperphosphorylation, oxidative stress, neuroinflammation, and synaptic losses. Despite extensive therapeutic investigations for many decades, the clinical treatment options remained largely symptomatic, while anti-amyloid antibody therapies were expensive and had limited accessibility. A subclass of triterpenoids generated from plants, pentacyclic triterpenic acids (PTAs), exhibited a variety of pharmacological properties. The neuroprotective effects of some important PTAs in AD models were reviewed in this study. These phytochemicals displayed a multimodal neuroprotection by lowering amyloid and tau, improving mitochondrial function, inhibiting inflammation, and improving synaptic plasticity and cognition. However, the neuroprotective mechanisms of several PTAs remained poorly characterized. In addition, most evidence were preclinical, while poor bioavailability and the limited clinical validation hindered the therapeutic translation. Studies were needed to evaluate these phytochemicals in AD, improve their pharmacokinetics, and enhance brain delivery. Their diverse bioactivities and encouraging preclinical findings suggest these compounds may serve as promising lead candidates for future drug development in neurodegenerative diseases.