Flavonoids and phenolic compounds: a promising avenue for neurodegenerative disease therapy.

Background/aim: Neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and ALS are characterized by a progressive loss of nerve cells, for which no definitive cure currently exists. These conditions share common pathological mechanisms, including chronic neuroinflammation, oxidative stress, protein aggregation, and mitochondrial dysfunction. Flavonoids and other plant-derived phenolic compounds have recently attracted attention for the treatment of such conditions due to their antiinflammatory and antioxidant properties. This review explores the neuroprotective mechanisms of flavonoids and evaluates their potential for the prevention and treatment of neurodegenerative diseases. Materials and methods: A literature search of the Web of Science, PubMed, and ScienceDirect databases was conducted to evaluate the therapeutic potential of flavonoids and phenolic compounds against neurodegenerative diseases. The search terms included "polyphenols", "flavonoids", and related compounds, along with "Alzheimer's", "Parkinson's", "Huntington's", and "Amyotrophic lateral sclerosis". Eligible studies included clinical trials, randomized controlled trials, and in vitro and in vivo research published in English. Priority was given to studies from the last decade, although older but significant publications were also included. Results: The findings of multiple studies report the ability of flavonoid compounds such as quercetin, myricetin, apigenin, and epigallocatechin gallate (EGCG) to modulate critical signaling pathways, reduce oxidative stress, prevent the accumulation of neurotoxic proteins, and support mitochondrial function. These bioactive molecules have exhibited significant potential in slowing disease progression and preserving neuronal integrity. Their therapeutic application, however, has been limited by their poor bioavailability, low stability, and rapid metabolism. Conclusion: Flavonoids have shown promise as naturally derived agents with multi-targeted activity against neurodegenerative processes. Enhancing their absorption and stability through novel delivery systems and structural modifications could significantly improve their clinical efficacy. When administered early or as a complementary therapy, flavonoids can be considered a safe and effective approach to the management of neurodegenerative diseases.