*Article* **Healthspan Enhancement by Olive Polyphenols in** *C. elegans* **Wild Type and Parkinson's Models**

**Gabriele Di Rosa 1,**†**, Giovanni Brunetti 1,**†**, Maria Scuto 1, Angela Trovato Salinaro 1, Edward J. Calabrese 2, Roberto Crea 3, Christian Schmitz-Linneweber 4, Vittorio Calabrese 1,\* and Nadine Saul <sup>4</sup>**


Received: 11 May 2020; Accepted: 26 May 2020; Published: 29 May 2020

**Abstract:** Parkinson's disease (PD) is the second most prevalent late-age onset neurodegenerative disorder, affecting 1% of the population after the age of about 60 years old and 4% of those over 80 years old, causing motor impairments and cognitive dysfunction. Increasing evidence indicates that Mediterranean diet (MD) exerts beneficial effects in maintaining health, especially during ageing and by the prevention of neurodegenerative disorders. In this regard, olive oil and its biophenolic constituents like hydroxytyrosol (HT) have received growing attention in the past years. Thus, in the current study we test the health-promoting effects of two hydroxytyrosol preparations, pure HT and Hidrox® (HD), which is hydroxytyrosol in its "natural" environment, in the established invertebrate model organism *Caenorhabditis elegans*. HD exposure led to much stronger beneficial locomotion effects in wild type worms compared to HT in the same concentration. Consistent to this finding, in OW13 worms, a PD-model characterized by α-synuclein expression in muscles, HD exhibited a significant higher effect on α-synuclein accumulation and swim performance than HT, an effect partly confirmed also in swim assays with the UA44 strain, which features α-synuclein expression in DA-neurons. Interestingly, beneficial effects of HD and HT treatment with similar strength were detected in the lifespan and autofluorescence of wild-type nematodes, in the neuronal health of UA44 worms as well as in the locomotion of rotenone-induced PD-model. Thus, the hypothesis that HD features higher healthspan-promoting abilities than HT was at least partly confirmed. Our study demonstrates that HD polyphenolic extract treatment has the potential to partly prevent or even treat ageing-related neurodegenerative diseases and ageing itself. Future investigations including mammalian models and human clinical trials are needed to uncover the full potential of these olive compounds.

**Keywords:** *C. elegans*; polyphenols; olive oil; healthspan; lifespan; ageing; Parkinson's disease
