Rethinking Alzheimer's Disease Therapy: From Amyloid-Centric Approaches to Multi-Target Phytochemical Strategies

Alzheimer's disease (AD) is the leading cause of dementia, characterized by irreversible neuronal loss and progressive cognitive decline. The disease is driven by complex and interconnected pathological processes, including amyloid-β plaque deposition and tau neurofibrillary tangle formation, which converge on neuroinflammation, oxidative stress, synaptic dysfunction, and widespread neuronal network failure. Although recently approved antibody-based therapies such as lecanemab and donanemab effectively reduce cerebral amyloid burden, their clinical benefits remain modest and are accompanied by significant safety concerns, including amyloid-related imaging abnormalities (ARIA). Current pharmacological strategies predominantly rely on single-target mechanisms, an approach increasingly recognized as insufficient to address the multifactorial neurobiology of AD. This review critically evaluates the limitations of conventional amyloid-centric therapeutic strategies and contrasts them with emerging multi-target approaches based on phytochemicals. We synthesize current experimental and translational evidence to present a mechanistic framework illustrating how plant-derived bioactive compounds, including flavonoids and polyphenols, function as systems-level modulators of AD pathology rather than purely symptomatic agents. Particular emphasis is placed on their coordinated actions on amyloid processing via BACE1 inhibition, restoration of tau homeostasis through GSK-3β/PP2A regulation, attenuation of neuroinflammatory signaling, enhancement of endogenous antioxidant defenses through Nrf2 activation, and preservation of synaptic integrity. When considered collectively, the available evidence supports the concept that multi-target phytochemical strategies represent a biologically congruent and neurologically relevant paradigm for Alzheimer's disease therapy. Future progress will likely depend on integrating these compounds into broader polypharmacological and multidomain intervention frameworks, together with lifestyle-based strategies, repurposed drugs, anti-amyloid therapies, and rigorous translational validation.