Olea europea and By-Products: Extraction Methods and Cosmetic Applications

Currently, in addition to the use of olive oil in cosmetics, the use of olive-derived bioactives and their incorporation into cosmetics is a growing trend. The olive oil industry produces vast quantities of by-products, such as olive mill wastewater, olive pomace and leaves from which new ingredients may be obtained for cosmetic use. In this way, by-products are revalorized, which contributes to the implementation of a sustainable economy or upcycling. This review intends to provide a detailed overview of the different extraction techniques reported in order to obtain the bioactive compounds of cosmetic value that can be found in olive by-products: fatty acids, tocopherols, polyphenols, phytosterols and squalene. Different extraction techniques are presented, including some traditional techniques (solid–liquid extraction) and more novel or “greener” ones: ultrasound, microwave, supercritical extraction, pressurized fluids and deep eutectic solvents. Additionally, different applications of olive by-products in skin care products are explored: emollient, antioxidant, anti-age, anti-inflammatory, antiviral, antifungal and antibacterial, and the perspective of consumers is also considered since they increasingly demand products formulated with natural ingredients.