Polyphenol-hydrogen peroxide reactions in skin: In vitro model relevant to study ROS reactions at inflammation

Antioxidants are important to protect and maintain biological barriers, such as the skin. Antioxidant effects are often assessed using clinical trials, however these tests are costly and time consuming. In this work we introduce a skin membrane-covered oxygen electrode (SCOE) as an in vitro tool for monitoring H₂O₂ and antioxidant reactions in skin. The SCOE gives amperometric response to H₂O₂ concentrations down to 0.05 mM. More importantly, the electrode allows measurements of polyphenol penetration and reaction with H₂O₂ in skin. Measurements with SCOE show that lipophilic polyphenols such as quercetin, piceatannol, resveratrol, and plant extract from Plantago major impose their antioxidant effect in skin within 2-20 min. Rutin is however too hydrophilic to penetrate into stratum corneum and therefore cannot deliver its antioxidant effect during similar time interval. The measurements are interpreted considering polyphenol partition-penetration through stratum corneum and the reaction with the H₂O₂-catalase system in the skin. The contribution of other enzymes will be addressed in the future.