**9. Conclusions**

The evidence presented in this review demonstrates the several biological activities of oleuropein including antioxidant, anti-inflammatory and anticancer properties. Several epidemiological studies have reported a strict association between a diet rich in this polyphenol and the prevention of several NCDs, that are among the main causes of morbidity and mortality in the world. In conclusion, several in vitro and in vivo studies have demonstrated the ability of oleuropein (and its derivatives) to counteract oxidative stress and inflammation, to modulate the autophagy pathway, as well as to interfere in the amyloid aggregation process, suggesting its use, not only in the prevention, but also as a complementary therapy of some diseases. Despite the low bioavailabilty of oleuropein, some clinical trials reported several beneficial effects after administration of this compound, confirming the results obtained in vitro and in vivo studies. The effective daily dose of oleuropein to be administered in humans to achieve a theraputic effect is not known, but clinical and experimental evidence sugges<sup>t</sup> that regular intake of this compound can be effective in the long term, representing a continuous low-intensity stimulus to the cellular defence against NCDs [186].

**Author Contributions:** Conceptualization, C.N.; writing—original draft preparation, C.N., J.R., L.C. and A.R. writing—review and editing, C.N. and J.R.; supervision, C.N.; funding acquisition, C.N. and L.C. All authors proofread the manuscript.

**Funding:** This study was financially supported by grants from Istituto Toscano Tumori and Ente Cassa di Risparmio di Firenze.

**Acknowledgments:** The authors thanks Annalisa Noce and Giulia Morrone for their critical revision, and Marcella Tarducci for the revision of the English language.

**Conflicts of Interest:** The authors declare no conflict of interest.
