Extraction, purification, characterization and antioxidant activities of polysaccharides from Cistanche tubulosa

• The CTP yield in UCE and polysaccharide content increased to 44.96% and 70.13%, respectively.
• CTP extracted by HWE, EAE, UAE and UCE were consisted of Rha, Man, Glc and Gal by GC with different ratios.
• CTPs have fundamentally identical functional groups and different structures.
• The TGA and DSC exerted the thermostability of CTP in different temperatures.
• C. tubulosa polysaccharides showed a significant antioxidant activities in vitro.

An efficient ultrasonic-cellulase-assisted extraction (UCE) of Cistanche tubulosa polysaccharide (CTP) was established. The response surface methodology based on Box-Behnken Design was employed to further optimize extraction conditions. After quaternary ammonium salt precipitation, the polysaccharide of C. tubulosa was characterized by different techniques. The results showed that a maximum polysaccharide yield of 22.31 ± 0.45% was achieved at a pH of 5.2 for 31.5 min at 54.1 °C. Compared to hot water extraction, the yield of CTP in UCE and polysaccharide content increased to 44.96% and 70.13 ± 2.19%, respectively. There was no marked difference among polysaccharides extracted using different methods from the infrared spectrum. Ultrasonic-cellulase-assisted extraction polysaccharide showed a fibrous structure from scanning electron microscopy and was composed of rhamnose, mannose, glucose, and galactose in a molar ratio of 2.18:1:28.29:1.43 by gas chromatography. The circular dichroism results indicated that polysaccharides had a maximum positive peak around 210 nm with different peak values. The thermogravimetric analysis and differential scanning calorimetry were used to test the thermostability of CTP. Besides, CTP demonstrated appreciable antioxidant potential on antioxidant experiments in vitro. The results suggested that UCE is an effective method for CTP extraction and its polysaccharide showed appreciable antioxidant activity.