Ultrasonic-assisted enzymatic extraction and characterization of polysaccharides from dandelion (Taraxacum officinale) leaves

Ultrasonic-assisted enzymatic extraction (UAEE) technology was employed to extract the polysaccharides from dandelion leaves (DLP). The extraction conditions were optimized by response surface method (RSM) and Box-Behnken design (BBD). The polysaccharide yield (14.05 ± 0.95%), which well matched with the predicted value of 14.27%, was obtained under the optimum parameters: ultrasound power 500 W, ultrasound time 42 min, cellulase amount 4.90%, and particle size 80 mesh. After purification by AB-8 Macroporous Resin and Sephadex G-100 column, a novel polysaccharide (DLP-I) was isolated and its molecular weight was estimated to be 87,000 g/mol by high performance liquid chromatography (HPLC). Gas chromatography (GC) analysis showed that DLP-I was composed of rhamnose, arabinose, mannose, galactose and glucose in the molar ratio of 1.14:1.00:1.05:4.76:1.52. 1D and 2D NMR spectra confirmed that the backbone of DLP-I was mainly consisted of →4)-α-D-Galp-(1→, →4)-β-D-Manp-(1→, →4)-α-D-Glcp-(1→, →2,4)-α-L-Rhap-(1→, and α-L-Araf-(1→ with branching at O-2 and O-4 of →2,4)-α-L-Rhap-(1→. In addition, the digestion results showed DLP-I could keep its stability during the simulated digestive juices.