Initial assessment of the genetic control of virgin cork polar extractives

Cork oak (Quercus suber) covers 22% of the Portuguese forest area. This Mediterranean agroforestry system generates diverse goods and services, Portugal being the world’s largest cork producer. Cork, the outer layer that covers the trunk of the cork oak tree, is well known as the raw material of bottle stoppers. However, as it is rich in phenolic compounds, with potential clinical applications, due to its antioxidant, anti-inflammatory, anticancer and antimicrobial properties. We aimed to evaluate the genetic control over the production of bioactive compounds in cork as one of the factors consistently reported is the high variability at tree level. In that way, we made use of the Q. suber genetic field trial established in 1998 at “Herdade do Monte Fava” (Ermidas-Sado), in which distinct growth patterns were observed for the several provenances. To the best of our knowledge, this is the 1^st time that genetic variability on cork bioactivities is evaluated. Following an aqueous extraction procedure developed in our lab, we extracted polar components from corks trees grown at “Monte Fava“from the Q. suber provenances PT20 (Portugal), ES07 (Spain) and IT09 (Italy). Antimicrobial activity assays showed that the extracts were able to inhibit the growth of Staphylococcus aureus, Escherichia coli and Cryhonectria parasitica. Extracts from different provenances showed distinct minimum inhibitory concentration (MIC) values. Furthermore, the extracts that presented higher antomicrobial activity, also have higher redox equivalentes content (as estimated by Folin-Ciocalteu method). We further tested the protective role of cork extractives in SH-SY5Y neuroblastoma cells against MPP⁺-induced toxicity, and the preliminary data point for an antioxidant role for some of the extracts. Our approach revealed that while there is variability at the tree level, there are differences between tree provenances in relation to their antimicrobial and antioxidant potential.