Wild Olea europaea Leaves as an Alternative Source of Antioxidant and Anti-Inflammatory Compounds to Cultivated Olive Tree Leaves for Cosmetic Ingredients

This study assessed the potential of Oleaster leaves as a valuable cosmetic ingredient by comparing aqueous and hydroalcoholic ultrasound-assisted extracts of Oleaster leaves to those of the Olive tree. The hydroalcoholic Oleaster leaf extract showed a higher content in phenolic and flavonoid compounds, with an oleuropein and verbascoside content of 58 mg/g of dry leaves and 3.2 mg/g of dry leaves, respectively. To refine the comparison of their molecular composition, the extracts were analyzed using UHPLC-HRMS/MS. About twenty compounds, including secoiridoids, flavonoids and triterpenic acid derivatives, were annotated in both extracts, demonstrating their similarity. DPPH, CUPRAC and enzymatic SOD assays showed a good antioxidant activity with high inhibition (60–90%) for both Oleaster and Olive tree leaf extracts. The hydroalcoholic extracts at 62.5 µg/mL also exhibited 60–80% of protection against reactive oxygen species (ROS) in H2O2-stressed HaCaT cells, confirming this antioxidant capacity without demonstrating a severe cytotoxicity, which remained below 40%. The anti-inflammatory potential of the extracts was also demonstrated using COX-2 inhibition, which was around 70%, and by measuring the concentration of IL-8 in HaCaT cells under pro-inflammatory conditions, which decreased in the presence of extracts at a concentration of 50 pg/mL, similar to that observed for the positive control. Thus, the hydroalcoholic ultrasound extract of Oleaster leaves demonstrated its high potential to develop sustainable and active cosmetic ingredients.