Preparation, characterization and bioactivity of polysaccharide fractions from Sagittaria sagittifolia L.

To ascertain the preliminary structural characteristics and biological activity of different fractions of polysaccharides from Sagittaria sagittifolia L. (SPCs) by ultrasonic assisted extraction (UAE), four new polysaccharides (SPC-60, SPC-70, SPC-80 and SPC-90) were successively fractionated by ethanol. The results implied that except for neutral sugar, four contained proteins and uronic acids in their structure, which were further confirmed by the ultraviolet and infrared spectra. Molecular weight and monosaccharide composition analysis exhibited that SPC-60 (52.0 kDa), SPC-70 (294.9 kDa), SPC-80 (230.6 kDa) and SPC-90 (229.4 kDa) were a neutral polysaccharide composed of rhamnose, arabinose, xylose, mannose, glucose and galactose with dramatically different mole ratios. In addition, SPC-70 exhibited stronger antioxidant activity in vitro than the other three components. SPCs could significantly promote macrophage proliferation, NO release and phagocytosis. Thus, these results provided a reference for applications of S. sagittifolia L. polysaccharides which would benefit the development of industry and agriculture.