Dietary polyphenol oleuropein and its metabolite hydroxytyrosol are moderate skin permeable elastase and collagenase inhibitors with synergistic cellular antioxidant effects in human skin fibroblasts

Abstract

Oleuropein (OLE) and hydroxytyrosol (HT) are dietary polyphenols with skin beneficial effects but their effects on skin-ageing-related enzymes are not clear. Herein, we evaluated their inhibitory effects on elastase and collagenase. OLE and HT (62.5–1 000 μM) showed moderate anti-elastase and anti-collagenase effects (5.1–26.3%, 5.8–12.2% and 12.6–31.0%, 11.6–31.9% inhibition, respectively). Combinations of OLE and HT (1:1 ratio) exerted synergistic inhibitory effects on elastase, which were supported by their combination index (CI), kinetic assay and computational docking. Moreover, HT (100 μM) reduced hydrogen peroxide (H₂O₂)-induced cytotoxicity and reactive oxygen species (ROS) in human dermal fibroblast cells by 21.8 and 15.2%, respectively. In addition, combinations of OLE and HT (6.25/6.25–100/100 μM) exerted synergistic cytoprotective effects by reducing ROS levels by 7.6–37.3% with CIs of 0.17–0.44, respectively. The findings from this study support the cosmeceutical activities of OLE and HT but further research is warranted to evaluate their anti-skin-ageing effects using in vivo models.

Keywords:

• Oleuropein
• hydroxytyrosol
• elastase
• collagenase
• skin protection

Acknowledgments

Spectrometric data were acquired from instruments located at the University of Rhode Island in the RI-INBRE core facility obtained from grant # P20GM103430 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH).

Conflicts of interest

The authors declare no conflict of interest.

Additional information

Funding

HL was supported by funding from the Department of Education of Guangdong Province [no: 2017KSYS010, 2019KZDZX2003] and the Jiangmen Program for Innovative Research Team [no: 2018630100180019806]. RL was supported by funding from the National Key Research and Development Program of Shaanxi [2018SF-151].