The antioxidant potential of Arbutus unedo tree berries from the Natural Park of Montesinho

Arbutus unedo L. is a native species of the Mediterranean region, commonly known as strawberry tree [1]. Traditionally, this species has been used for medicinal purposes [2], and the berries are not usually directly consumed but instead used for the production of alcoholic beverages and jams [3]. Strawberry tree berries are noted for their impressive nutritional profile, being rich in different bioactive compounds [2], which underpins their various pharmacological properties [4], such as antioxidant activity, drawing the attention of food, nutraceutical, and cosmetic industries [5].
This study’s goal is to develop an eco-friendly extract from A. unedo L. berries using a green approach. Briefly, in October 2022, berries were collected from Natural Park of Montesinho and then processed using an ultrasound-assisted extraction (UAE), using water as solvent and with an extraction intensity of 30 W/m². The impact of extraction time (15–90 minutes) was assessed on the total phenolic content (TPC), in vitro antioxidant/antiradical activities, reactive oxygen species (ROS) scavenging capacity, phytochemical profile, and keratinocytes viability.
The results highlighted that the 60-min extract exhibited, overall, the highest values for the antioxidant/antiradical activities (ABTS = 30.36 mg AAE/g dw; DPPH = 43.83 mg TE/g dw; FRAP = 415.61 μmol FSE/g dw) and TPC (30.27 mg GAE/g dw). Concerning the ROS scavenging capacity, this extract's IC50 values for hypochlorous acid and superoxide radical were 19.78 and 90.51 μg/mL, respectively, and 0.19 μmol TE/mg dw for peroxyl radical. The analysis of the phytochemical profile highlighted significant levels of gallic acid, catechin, and its derivatives. Moreover, the keratinocyte viability was higher than 90% after exposure to the highest concentration tested (1000 μg/ml). These findings highlight the potential of UAE-extracted A. unedo L. fruit as a valuable source of bioactive compounds suitable for use as an active ingredient in different industries.

Acknowledgments: This research was funded by MTS/SAS/0077/2020—Honey+—New reasons to care honey from the Natural Park of Montesinho: A bioindicator of environmental quality & its therapeutic potential, and by the projects UIDB/50006/2020, UIDP/50006/2020, and LA/P/0008/2020, all supported by Fundação para a Ciência e a Tecnologia (FCT)/Ministério da Ciência, Tecnologia e Ensino Superior (MCTES). This work was also financed by national funds from FCT—Fundação para a Ciência e a Tecnologia, I.P., in the scope of the project 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—i4HB. Ana Margarida Silva is thankful for the Ph.D. grant (SFRH/BD/144994/2019) financed by POPH–QREN and subsidized by the European Science Foundation and Ministério da Ciência, Tecnologia e Ensino Superior. F. Rodrigues (2023.06819.CEECIND) and M. Moreira (2023.05993.CEECIND) are thankful for their contracts financed by FCT/MCTES.

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