Characterization and purification of hypoglycemic components from Rubus suavissimus leaf by affinity ultrafiltration, molecular docking, and macroporous resin

This study developed an environmentally friendly method for extracting polyphenols and rubusoside from Rubus suavissimus leaves. Under optimal extraction conditions, the contents of polyphenol and rubusoside reached 91.89 ± 2.39 mg/g and 47.03 ± 1.45 mg/g, respectively. The extract was purified by twelve types of macroporous resins, among which the ADS-7 resin had the highest static adsorption and desorption capacities. Optimized purification parameters for ADS-7 resin were determined by static and dynamic adsorption-desorption experiments and found to be: loading flow rate, 3 BV/h; loading concentration, 10 mg/mL; loading volume, 24 BV; elution solvent, 80 % (v/v) ethanol; elution speed, 3 BV/h; and elution volume, 20 BV. After purification, the content of polyphenols and rubusoside increased by 2.63 and 2.32 times, respectively. Kinetic and thermodynamic analyses revealed distinct adsorption mechanisms: polyphenols followed a pseudo-second-order model, whereas rubusoside followed a pseudo-first-order model; both exhibited spontaneous (ΔG < 0) and endothermic (ΔH > 0) physisorption. Ultrafiltration-assisted centrifugal fractionation combined with UPLC-ESI-qTOF-MS/MS identified eight potential α-glucosidase inhibitors, including quercetin, apigenin, rutin, ellagic acid, kaempferol-3-O-rutinoside, kaempferol, rubusoside, and steviol. Molecular docking simulations revealed the molecular interactions between these compounds and α-glucosidase. The enriched extract demonstrated enhanced bioactivity, with a 3.35-fold higher α-glucosidase inhibition, and its IC₅₀ values for DPPH and ABTS⁺ radical scavenging decreased from 142.03 μg/mL to 88.45 μg/mL and from 197.63 μg/mL to 107.63 μg/mL, respectively. These results substantiate the effectiveness of the extraction-purification approach for producing R. suavissimus leaf extracts and suggest their potential application as functional hypoglycemic and antioxidant food ingredients.