For the roughly 50 million people worldwide living with Alzheimer's, Parkinson's, Huntington's disease, or ALS, approved treatments manage symptoms but leave the underlying neuronal destruction untouched. A growing body of phytochemical research now challenges that therapeutic ceiling by mapping how plant, fungal, and marine compounds interact with the very molecular machinery driving neurodegeneration — potentially offering disease-modifying effects rather than mere palliation.
This comprehensive review, drawing on peer-reviewed trials and experimental studies indexed across PubMed, Scopus, Web of Science, and Google Scholar, identifies four converging pathological drivers shared across neurodegenerative conditions: oxidative stress, neuroinflammation, mitochondrial dysfunction, and aberrant protein aggregation — the misfolding cascades that produce amyloid plaques, alpha-synuclein deposits, and huntingtin fibrils. Against these mechanisms, flavonoids, alkaloids, and terpenoids emerge as structurally diverse but functionally complementary agents capable of engaging multiple targets simultaneously, a pharmacological profile that single-molecule drugs rarely achieve.
The multitarget advantage of natural compounds is precisely what makes this review worth examining critically. Conventional drug development typically optimizes one molecule for one receptor, yet neurodegeneration is inherently a systems-level failure. Curcumin, resveratrol, berberine, and huperzine A — representatives of each compound class — have individually shown mechanistic promise in reducing tau hyperphosphorylation, inhibiting acetylcholinesterase, modulating NF-κB inflammatory signaling, and supporting mitophagy. However, the crucial limitation here is translational: most evidence remains preclinical, and bioavailability remains a persistent obstacle — oral curcumin, for instance, reaches negligible plasma concentrations without formulation enhancement. This review synthesizes a wide literature but does not resolve the gap between mechanistic elegance and clinical efficacy. For health-conscious adults, the findings support a diet rich in polyphenol-dense foods as a prudent longevity strategy while the harder translational science continues. This should be read as an encyclopedic synthesis rather than clinical guidance.
