Abstract
Background The above experimental results show that SBP-2A isolated and purified from Scutellaria barbata may be a candidate drug for further evaluation in cancer prevention, which provides a clue for further studies on the molecular mechanism of its anticancer activity against human liver cancer cells.Methods The crude polysaccharide of Scutellaria barbata (SBP) was extracted with water and precipitated with alcohol. Optimal extraction conditions were determined by response surface methodology: the solid-liquid ratio was 1:25, the extraction time was 2 h, and the extraction temperature was 90 °C. With these conditions, the average extraction efficiency was 3.85 ± 0.13%. SBP was purified with a DEAE-52 cellulose column and Sephadex G-100 dextran gel column to obtain SBP-1A and SBP-2A fractions. The polysaccharide content, molecular weight, monosaccharide composition and basic structure were preliminarily identified. Then, a MTT assay was used to identify the polysaccharide components with anti-hepatoma effects. The antitumor activity of SBP-2A was evaluated by colony formation tests, morphological observations, apoptosis and cell cycle analyses.Results Structural analysis showed that SBP-1A and SBP-2A were mainly composed of arabinose and galactose, but the molar ratios were different; these were homogeneous acidic polysaccharide components with high purity, and the average molecular weights were 1.15 × 105 Da and 1.4 × 105 Da, respectively. FT-IR spectra showed that SBP-1A and SBP-2A contained uronic acid β-glucan, and the sugar residue of the polysaccharide was mainly pyranose. MTT and colony formation assays showed that SBP-2A significantly inhibited the proliferation of HepG2 cells. The cell distribution at different apoptotic stages was determined by the Hoechst 33258 test and Annexin V-FITC/PI staining. Flow cytometric analysis showed that SBP-2A induced HepG2 cell apoptosis by blocking the G1 phase.Conclusions Two polysaccharides (SBP-1A and SBP-2A) had been isolated from Scutellaria barbata. Preliminary characterization of the SBP-1A and SBP-2A was investigated. The anticancer activities were studied in vitro. SBP-2A significantly inhibited the proliferation of HepG2 cells and induced cells apoptosis by blocking the G1 phase.