Characterization, antioxidant and immunomodulatory effects of selenized polysaccharides from dandelion roots

The polysaccharide (DRP) was gained from dandelion roots by ultrasonic-assisted enzymatic extraction (UAEE) followed by two-step column purification. Then selenylation of DRP has been accomplished by HNO3-Na2SeO3 method. sDRP-1 and sDRP-2 with the selenium content of 170 ± 1.13 and 710 ± 4.00 μg/g were prepared for further structural characterization and bioactivity determination. DRP, sDRP-1, and sDRP-2 were composed of the same monosaccharides in different molar ratios, and the molecular weights of DRP, sDRP-1 and sDRP-2 were 8700, 7900, and 5600 Da, respectively. Fourier transform infrared (FT-IR) spectra confirmed that DRP, sDRP-1, and sDRP-2 possessed similar functional groups. The results of Congo red test, X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that DRP, sDRP-1, and sDRP-2 had no three helix structure, did not form single crystal, and all belonged to amorphous morphology. sDRP-1 and sDRP-2 possessed greater antioxidant activities in vitro than the native polysaccharide DRP. At the same time, the selenized polysaccharides showed better immunomodulatory ability and could be used as new-type immunoenhancer. The present conclusions provided theoretical basis for the new application of dandelion polysaccharides and the development of dandelion resources.