Phenolic Composition and Antioxidant Activity of Leaves of Strawberry Tree (Arbutus unedoL.) Populations from Morocco

Abstract

This study was aimed at determining the phenolic composition and the antioxidant activity of leaves of Arbutus unedo populations belonging to seven Moroccan locations. Antioxidant activity is evaluated using two methods: scavenging effect on DPPH and scavenging effect on ABTS radicals. The Arbutus unedo leaf extracts displayed average values of 61.95 mg GAE, 3.60 mg QE, and 0.15 mg CE per g of dry weight (DW) in polyphenols, flavonoids, and tannins contents, respectively. All extracts exhibited a strong antioxidant effect on both assays, presenting mean IC50 values of 4.22 in DPPH assay and 4.86 μg/ml in ABTS assay. Significant variability (P < 0.0001) was showed among surveyed populations; samples from the Chefchaouen location (CH) was revealed the highest total phenolic content (107.67 mg GAE/g DW) and the strongest antioxidant activity (IC50 values of 0.80 and 1.56 μg/ml, in DPPH and ABTS tests, respectively). The phenolic profile achieved by HPLC-DAD-ESI/MS was dominated by gallic acid, Gallic acid glucose derivative, and Galloylquinic acid derivative. A significant negative correlation (P < 0.05) was observed between the total phenolic content and the antioxidant activity. These results provide that Arbutus unedo leaves should be considered as a promising source of natural antioxidants, and as ingredients in complimentary food and nutraceutical products.