Characterization and Comparative Assessment of the Antioxidant, Antidiabetic, and Antibacterial Potential of Polysaccharide Fractions Extracted from Arbutus unedo L. Fruit

Background: Arbutus unedo L., commonly referred to as the “strawberry tree”, is a Mediterranean species esteemed for its wealth of biologically active fractions and phytochemical compounds. Historically, the fruits, leaves, and roots of A. unedo have been utilized extensively for both ethnomedicinal and culinary applications. Objectives: The aim of this study was to characterize the structural properties of polysaccharides derived from Arbutus unedo L. and to systematically evaluate their antioxidant, antidiabetic, and antibacterial properties. Methods: Polysaccharide fractions were isolated from the fruit and characterized via Fourier-Transform Infrared (FTIR) spectroscopy. The antioxidant potential was determined by DPPH radical scavenging, Ferric Reducing Power (FRP), and Total Antioxidant Capacity (TAC). The antibacterial activity was assessed through the disk diffusion method, while the antidiabetic potential was evaluated in vitro via the inhibition of porcine pancreatic α-amylase. Results: Two distinct polysaccharide extracts, designated A. unedo P1 and A. unedo P2, were obtained, revealing heterogeneous chemical profiles. Notably, A. unedo P2 exhibited a higher total phenolic content than A. unedo P1. Conversely, A. unedo P1 demonstrated a stronger inhibitory effect against α-amylase (IC₅₀ = 1.97 ± 0.22 mg/mL) than A. unedo P2 (IC₅₀ = 5.66 ± 0.43 mg/mL). Similarly, A. unedo P1 demonstrated greater antioxidant capacity in the DPPH assay (IC₅₀ = 0.051 ± 0.002 mg/mL) and higher ferric reducing assays (IC₅₀ = 0.547 mg/mL) compared with A. unedo P2 (IC₅₀ = 0.395 ± 0.03 mg/mL and 3.56 mg/mL, respectively). Additionally, A. unedo P1 manifested substantial antibacterial activity. Conclusion: Despite its lower phenolic concentration, the A. unedo P1 fraction exhibited superior antioxidant, antidiabetic, and antibacterial properties compared to A. unedo P2. These findings underscore the potential of A. unedo P1 as a high-value natural bioactive ingredient for nutraceutical formulations and functional food applications. Keywords: Arbutus Unedo L.; Polysaccharides; Antibacterial Activity; Alpha-Amylase Inhibition; Strawberry Tree; Antioxidant Potential.