Isolation and structural characterization of a novel β-fructan with potent α-amylase inhibitory activity from Polygonatum multiflorum

This study reports the isolation and structural characterization of a novel β-fructan (PMP2) from Polygonatum multiflorum using sequential pressing, macroporous resin adsorption, and ultrafiltration (yield: 0.66 %; purity: 93.8 %). Structural analysis revealed a 4.06 kDa polymer with a fructose-dominated composition (Fru/Glu = 86.5:12.9), featuring a linear backbone of →1)-β-D-Fruf-(2→ with →6)-β-D-Fruf-(2→ and →1,6)-β-D-Fruf-(2→ branches, as confirmed by methylation and NMR. SEM revealed lamellar morphology at 400× magnification and porous fibrous structure at 2000×. PMP2 exhibited potent α-amylase inhibition (84.3 % at 0.25 mg/mL) and limited antioxidant activity (e.g., the DPPH scavenging rate was 15.51 ± 1.53 % at 10 mg/mL). Kinetic analysis confirmed competitive inhibition (3.1-fold Km increase; unchanged Vmax), while molecular docking demonstrated high-affinity binding (-17.6 kcal/mol) to the catalytic site through hydrogen bonding and steric blockade. The branching configuration correlates with enhanced enzymatic inhibition, positioning PMP2 as a structurally unique fructan for glycemia-control functional foods. These findings provide foundational data for P. multiflorum utilization.