This study aims at investigating the contribution of two classes of compounds, flavonoids and iridoids, to the bioactivity of Arbutus unedo L. leaves and fruits. The impact of different extraction procedures on phytochemicals content and hypoglycemic, antioxidant, and nitric oxide (NO) inhibitory activities of A. unedo fresh and dried plant materials was investigated. Ellagic acid 4-O-β-D-glucopyranoside, kaempferol 3-O-glucoside, and norbergenin were identified for the first time in this genus by using liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (LC-ESI-QTOF-MS). Three iridoids (gardenoside, geniposide, unedoside) are specifically identified in the leaves. Interestingly, asperuloside was extracted only from dried fruits by ethanol with Soxhlet apparatus. Extracts were screened for their potential antioxidant activities by using the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Activity Power (FRAP), and β-carotene bleaching tests. Based on the Global Antioxidant Score (GAS) calculation, the most promising antioxidant extract was obtained by hydroalcoholic maceration of dried leaves that showed half maximal inhibitory concentration (IC50) of 0.42 and 0.98 μg/mL in ABTS and DPPH assays, respectively. The hypoglycaemic activity was investigated by α-amylase and α-glucosidase inhibition tests. Extracts obtained by ethanol ultrasound extraction of fresh leaves and hydroalcoholic maceration of fresh fruits (IC50 of 19.56 and 28.42 μg/mL, respectively) are more active against α-glucosidase than the positive control acarbose (IC50 of 35.50 μg/mL). Fruit extracts exhibited the highest anti-inflammatory activity.

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This work investigated a model for the reuse of Citrus × clementina Hort. by-products for the development of a functional drink able to exert antioxidant, hypoglycaemic, and hypolipidemic effects. Juice obtained from fruits collected in three different areas of Calabria (Italy) was analysed. C. × clementina juice from Corigliano Calabro (JF), characterized by the highest content of bioactive compounds and bioactivity, was chosen as a matrix to be enrichment with hydroalcoholic ultrasound-assisted maceration of C. × clementina leaf from Corigliano Calabro (CO2) and ethanol ultrasound-assisted maceration of C. × clementina peel from Cetraro (BC3) extracts at different concentrations. The highest phytochemical content and bioactivities were found in juice enriched with leaf and leaf + peel extracts, with particular reference to antioxidant activity. In order to estimate the effects of pasteurization, 20% (mg/100 mL) enriched juice was subjected to this process. Based on obtained data of bioactivity and sensorial analysis, C. × clementina by-products could be proposed as a promising source of bioactive compounds useful for the formulation of a functional drink for preventing diseases associated with oxidative stress such as type 2 diabetes and obesity.