Optimization of extraction process from Taraxacum officinale polysaccharide and its purification, structural characterization, antioxidant and anti-tumor activity

In order to get high yield polysaccharide from Taraxacum officinale, single factor experiment and an orthogonal experiment were applied to optimize the best extraction conditions. In this experiment, a novel comparison was made to explore and compare the effect of enzyme assisted and ultrasonic assisted hot water extraction of polysaccharide from T. officinale. The optimum conditions were as follows: raw material to water: 1:15, extraction temperature: 65 degrees C, extraction time: 2 h and ultrasound assisted, and the experimental extraction yield was 6.46% +/- 0.19% (n = 3). A novel neutral polysaccharide (TOP, about 1.7 x 10(3) Da) was isolated from the T. officinale, which contents of total sugar, uronic acid and protein were 90.16%, 0.17% and 0.26%, respectively. Monosaccharide analysis, Methylation analysis and NMR analysis revealed that TOP had a backbone composed of (1 -> 4)-beta-D-Glcp with branching at O-2 of (1 -> 2,4)-beta-D-Glcp and four main branches of (1 -> )-beta-D-Glcp (1 -> 3)-alpha-D-Galp (1 -> 3)-alpha-D-Manp and (1 -> )-alpha-L-Araf units. Additionally, the antioxidant activity suggested that TOP had great antioxidant effect, especially scavenging activity for DPPH radical and reducing power. TOP polysaccharide has anti-tumor activity, which can inhibit the proliferation of HepG2 cells. This study has shown that TOP can be explored as a novel natural antioxidant and anti-tumor drug.