## 6 Conclusions  
Cork obtained from _Q. suber_ bark represents a natural and sustainable resource for various applications since its extraction does not harm the tree. The cork industry is also considered sustainable since most of the cork by-products that are formed during the process are reused to self-sustain the factory. However, the main problem inherent to this industry is the amount of waste generated throughout the process. For this reason, a new perspective on the potentialities of cork by-products aroused to take full advantage of its properties. Cork and its by-products are currently being studied for pharmaceutical and cosmetic application. Cork extract composition encompasses several compounds from different chemical families, thus attracting attention due to the different biological activities, translating into a variety of possible applications.  
The growing concern for the environmental footprint is also reflected on the skin care market where consumers started to demand more natural and sustainable products. Cork extracts have a considerable number of bioactive compounds, especially phenolics. Cork  
Figure 7: Potential cork cosmetic applications.  
phenolics, such as caffeic, gallic, ellagic, ferulic, vanillic, and protocatechuic acids, show remarkable antioxidant activity, owing to their radical-scavenging properties. Currently, cork and some cork extracts are already used in antiaging cosmetics and as mild exfoliiants and are registered as cosmetic ingredients in official databases.  
Even taking into account all the studies already carried out regarding cork and its by-products and their current applications, there is still room for innovation in this area. Although the results of in vitro studies on cork extracts are promising, they are still very preliminary, and it is necessary to conduct more studies to prove their effectiveness and safety for skin applications, namely studies to support skin depigmentation and anti-acne and antimicrobial claims as well as toxicological studies, according to the European Cosmetics Regulation No 1223/2009, \"The SCCS Notes of Guidance for the Testing of Cosmetic Ingredients and their Safety Evaluation\" and \"Technical Document on Cosmetic Claims\" [101; 102; 103]. In addition, more specific studies are needed regarding the analysis of bioactive compounds in cork by-products, such as cork powder, \"black condensate\", and cork-cooking wastewater. Clearly, cork is an important resource for the cosmetic industry, but further studies are needed to unveil and confirm the full spectrum of its potentialities.  
S.M. and C.P.: investigation, data curation, writing-original draft preparation; S.C., J.R.e.S., C.A. and J.M.S.L.: writing--review and editing, project administration; H.C., M.E.T., and I.F.A.: supervision, conceptualization, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This work was financed by national funds from the European Regional Development Fund (ERDF) through the Northern Regional Operational Programme (NORTE2020) under the project 47239--Cork2 Cosmetic (NORTE-01-0247-FEDER-047239). [PERSON] and [PERSON] acknowledges the research fellowship (NORTE-01-0247-FEDER-047239), fully supported by national funding from project 47239-Cork2 Cosmetic (NORTE-01-0247-FEDER-047239).  
This work was supported by national funds from FCT--Fundacao para a Ciencia e a Tecnologia, I.P. in the scope of the projects, UIDP/04378/2020 and UIDB/04378/2020 of the Research Unit on Applied Molecular Biosciences--UCIBIO, and the project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy--iHB. This research was also supported by national funds from FCT though the projects, UIDB/04423/2020 and UIDP/04423/2020 (Group of Natural Products and Medicinal Chemistry-CIIMAR), and the European Regional Development Fund (ERDF) through the COMPETE--Programa Operacional Fatores de Competitividade (POFC) program in the framework of the program, PT2020.  
The authors declare no conflict of interest.