Biological profiles of Q. cerris, Q. dalechampii, and Q. robur bark extracts: A characterization study

Objective: The main objective of the present study was to characterize the extracts obtained from the bark of three oak species in order to assess their use in potential cosmetic products.
Methods: The extracts were obtained from the oak barks (periderm and rhytidome) using ultrasound-assisted extraction. The total polyphenolic content was assessed afterward, using the Folin–Ciocâlteu method, while the antioxidant capacity was determined using methods based on the neutralization of the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radicals. To assess the tyrosinase inhibitory effect, a protocol using L–DOPA as the substrate of the enzyme was employed.
Results: The extracts presented high levels of polyphenolic compounds, with Q. cerris having the highest content. Because of the high concentration of the extracts in polyphenolic compounds, they revealed a great reducing capacity against both DPPH and ABTS radicals, but unfortunately the tyrosinase inhibitory activity of the tested extracts was very weak compared to the positive control.
Conclusions: The extracts may have beneficial effects when used in cosmetic products because of the antioxidant effects, but more studies must be conducted for the determination of the main phytochemical compounds comprised in the extracts and their correlation to the biological effects.