Decolorization affects the structural characteristics and antioxidant activity of polysaccharides from Thesium chinense Turcz: Comparison of activated carbon and hydrogen peroxide decolorization

Different decolorization methods have different effects on the properties of polysaccharides. In this study, polysaccharides extracted from Thesium chinense Turcz (T. chinense) were decolorized using either hydrogen peroxide (H2O2), which has been previously reported, or activated carbon. To begin, the conditions for decolorization by activated carbon were optimized through single factor experiments and orthogonal modeling and were predicted to be best at 0.5% (w/w) activated carbon, pH 5.0 and 40 °C in a water bath for 60 min. Following treatment by the two methods, the structures of the decolorized polysaccharides were compared. The samples treated by activated carbon (CTP) had higher molecular weight (Mw: 3.064 × 105 g/mol) and more sulfate groups (14.33%, w/w), whereas the samples treated by H2O2 (HTP) had lower Mw (8.349 × 104 g/mol) and more uronic acid (35.02%, w/w). The antioxidant capacities of the two samples were analyzed by free radical scavenging (DPPH, hydroxyl and ABTS) and cell antioxidant activity (CAA). The HTP showed a better scavenging effect on free radicals and a higher CAA. Together, the results showed that various decolorization methods differentially influence the characteristics of the polysaccharides extracted from T. chinense.