Extraction, structural features, and in vitro bioactivities of polysaccharides from Prunus padus L. berries

Prunus padus L. berries represent an undervalued temperate medicinal fruit with established ethnobotanical applications, yet comprehensive research on its endogenous polysaccharides remains absent. This study established an ultrasound-assisted hot-water extraction protocol optimised via Box-Behnken response surface methodology (RSM-BBD), achieving a crude polysaccharide yield of 13.46%. Two homogeneous polysaccharide fractions (PPLP2, PPLP3) were isolated using DEAE anion-exchange chromatography. Multi-spectroscopic and chromatographic characterisation revealed distinct backbone architectures: PPLP2 (4.6 kDa) is a neutral β-linked arabinogalactan, while PPLP3(4.4 kDa) is an acidic α-type pectic polysaccharide rich in galacturonic acid, as confirmed by FT-IR spectral analysis. In vitro tests revealed dose-dependent radical-scavenging and anti-carbohydrase effects for both fractions. PPLP3 exhibited superior antioxidant activity (IC₅₀: DPPH^· = 1.25 mg mL^-1, ABTS^+· = 0.98 mg mL^-1, hydroxyl radical = 1.42 mg mL^-1). At 1.0 mg mL^-1, both polysaccharides inhibited >80% α-amylase and α-glucosidase activity, with respective IC₅₀ below 0.032 and 0.02 mg mL^-1. This work constitutes the first integrated structural and biofunctional characterisation of P. padus berry polysaccharides, providing empirical evidence for their development as natural antioxidant and antihyperglycemic nutraceutical ingredients.