**5. Conclusions**

Besides all beneficial abilities of stilbenes, such as antioxidant activity, they may also have potential toxic effects. In this regard, the present work entail the first approach to the toxicological studies required before being used in wines. The cytotoxicity study evidenced that the stilbene extract reduced cell viability in both cell lines in the range of concentrations from 40–100 μg/mL after 24 h of exposure and from 30–100 μg/mL at 48 h of exposure. In addition, ultrastructural changes were observed from 15.6 μg/mL in HepG2 cells and 27.9 μg/mL in Caco-2 cells, which highlighted the higher sensitivity of the morphological study in comparison to the cytotoxicity endpoints. Moreover, this work also presents a wide assessment of the prooxidant and antioxidant profile of our extract in human cells, which had not been previously studied. In general, at the exposed concentrations, the extract presented a protective and reductive role against an induced oxidative stress. Taking into account all these findings as a starting approach, more research is needed to establish effective and safe concentrations of this stilbene extract intended to be used in wines as a preservative.

**Author Contributions:** Formal analysis, C.M.-P., T.R. and E.C.-V.; Funding acquisition, S.P. and E.C.-V.; Investigation, C.M.-P., M.P., F.J.M. and T.R.; Methodology, C.M.-P., M.P., F.J.M. and T.R.;; Project administration, E.C.-V. and S.P.; Resources, T.R. and E.C.-V.; Supervision, M.P. and S.P.; Writing—original draft, C.M.-P., F.J.M. and S.P.; Writing—review & editing, C.M.-P., T.R., E.C.-V. and S.P.

**Funding:** This work was supported by the Ministerio de Economía, Industria y Competitividad and INIA for the financial support for this project (RTA2015-00005-C02-02). Moreover, it was also supported by the Bordeaux Metabolome Facility and MetaboHUB (ANR-11-INBS-0010 project).

**Acknowledgments:** The authors thank the CITIUS Biology Service (University of Seville) for the technical assistance offered. Moreover, we would like to thank M.M. Merchán-Gragero, M-L. Iglesias and A. Palos-Pinto for their technical assistance.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
