**5. Conclusions**

Due to their different actions in terms of lifespan during non-stressful conditions, disparate modes of actions could be the underlying cause of the beneficial characteristics of the olive polyphenols OLE and HT. Accordingly, possible additive or even synergistic effects by combining both polyphenols should be studied in the future. Intense research in the last decade has provided increasing knowledge of the biochemical and cell biology basis of the beneficial effects of plant, notably olive polyphenols. Such growing information indicates that these polyphenols have the potential as promising tools to be used to develop new therapeutic and preventive approaches against ageing and ageing-associated neurodegenerative diseases. However, even though *C. elegans* and mammalian models are frequently used to test possible human treatments, human clinical trials are still needed to verify this assumption.

**Author Contributions:** Conceptualization, V.C. and N.S.; methodology, N.S. and C.S.-L.; validation, N.S., C.S.-L., V.C.; formal analysis, G.B., G.D.R.; investigation, G.B., G.D.R.; resources, V.C., M.S. (Maria Scuto), M.L., M.S. (Massimo Stefani); writing—original draft preparation, G.B., G.D.R. and N.S.; writing—review and editing, V.C., C.S.-L., M.S. (Massimo Stefani), M.L.; supervision, N.S. and V.C.; funding acquisition, N.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement No 633589 (Aging with Elegans). This publication reflects only the authors' views and the Commission is not responsible for any use that may be made of the information it contains. Furthermore, ML is granted by the Italian Airalzh Association (Reg. n◦ 0043966.30-10- 359 2014-u)**.**

**Acknowledgments:** We thank the Caenorhabditis Genetics Centre (CGC), which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440) and the Caldwell laboratory, University of Alabama for the supply of the *Caenorhabditis elegans* strains. Furthermore, we thank Thea Böttcher and Shumon Chakrabarti for their support in the lab. Not least, a special thanks goes to Christian E.W. Steinberg who enabled this project and cooperation.

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