Oleuropein: a narrative review on its role in neurodegenerative diseases

Olive oil, a cornerstone of the Mediterranean diet, contains trace amounts of oleuropein, a polyphenolic compound and its active metabolite hydroxytyrosol, which exhibit significant neuroprotective effects by reducing oxidative stress and brain inflammation. These properties make them promising for managing neurodegenerative diseases such as Alzheimer’s disease. This review synthesizes the current literature on the chemistry, biosynthesis, and neuroprotective activities of oleuropein and hydroxytyrosol, emphasizing their antioxidant and anti-inflammatory effects. Research indicates that hydroxytyrosol is bioavailable and rapidly distributed throughout the body, including brain tissue, due to its ability to cross the blood-brain barrier. In contrast, oleuropein requires metabolic conversion for bioavailability. Both compounds have been shown in preclinical animal studies to mitigate oxidative stress, promote autophagy, and facilitate the clearance of amyloid-beta aggregates. Moreover, they have been found to alleviate mitochondrial damage and dysfunction, which are critical factors in neurodegeneration. In animal and human studies, oleuropein and hydroxytyrosol have improved cognitive function, reduced neuroinflammation, and improved overall brain health. The mechanisms underlying these effects include the restoration of redox balance and the modulation of inflammatory pathways in the aging brain. Despite these promising findings, human clinical trials are needed to assess the long-term safety and efficacy of oleuropein and hydroxytyrosol in clinical settings. Understanding their role in neuroprotection could lead to effective interventions for preventing or slowing cognitive decline associated with aging and neurodegenerative diseases. Overall, oleuropein and hydroxytyrosol represent a compelling area of study within the realm of antioxidants and their application in neuroprotection.