Microwave-Assisted Degradation of Polysaccharide from Polygonatum sibiricum and Antioxidant Activity.

Four polysaccharide fractions (P-1: 71.40%, P-2: 1.95%, P-3: 1.14%, P-4: 1.64%) were isolated from crude Polygonatum sibiricum polysaccharide (PSP), processed by water extraction, ethanol precipitation, and further separated with diethylaminoethyl cellulose-52 anion-exchange chromatography. Their molecular weights and monosaccharide compositions were characterized by high performance gel chromatography with evaporative light scattering detector and ultraviolet-visible detector. The antioxidant activity of four polysaccharides fractions were assessed by the electron transfer menchanism (DPPH, ferric reducing power, and ABST assays) and chelation of transition metals (Fe²⁺ and Cu²⁺ chelation ability). The highest content fraction P-1 exhibited the lowest antioxidant activity, and the ranking of antioxidant capacity was P-4 > P-3 > P-2 > PSP > P-1. After processed by microwave-assisted degradation, the molecular weight of P-1 was decreased from 2.99 × 10⁵ to 2.33 × 10³ Da, while the antioxidant activity of degraded P-1 was about eightfold higher than natural P-1. These results indicated that the proposed microwave-assisted degradation approach was an efficacious methodology to improve their bioactivity by lower the molecular weight of polysaccharides. PRACTICAL APPLICATION: This study provided an environmentally friendly, convenient and efficient microwave-assisted degradation technology to process the neutral polysaccharides from Polygonatum sibiricum. The results could be used for the development and utilization of various plant polysaccharides as a kind of food supplement in our daily life.